New Circuits Page 213
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The Gate Boost SE uses a 1381, a 2N7000 MOSFET and a 2N3906 with a unique voltage doubler to increase the voltage applied to the gate of the MOSFET. Normally the 2.6V output of a 1381C is barely able to turn on the 2N7000. As a result the "on....
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The circuit is based on a low noise, high gain two stage PNP and NPN transistor amplifier, using DC negative feedback through R6 to stabilize the working conditions quite precisely. Output level is attenuated by P1 but, at the same time, the stage gain is....
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This encoder uses a single contact per key keyboard and provides all other switching function electronically. The diode between terminals 8 and 15 prevents the output going more than 1 volt negative with respect to the negative supply V-..
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This is a circuit for controlling the speed of small DC motors, it works nicely as a speed controller for an HO or N gauge model railroad...
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This circuit uses two transistors and one IC (555 timer IC) to produce a pulsating ultrasonic frequency. Transistors Ql and Q2 are connected in a direct-coupled oscillator. The frequency of that oscillator is set by capacitor CI. The oscillator output is....
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The timing must be exact to get those high voltage spikes. I used a tiny magnet on the rotor, that triggered a reedswitch allowing the relay to pulse the energy from the recovery coil to the primary battery. In the same time the rest of the circuit is....
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The NE570 can be used to make a high performance compressor FTA, except that the rectifier is connected to the input. This makes gain inversely proportional to the input level so that a drop of 20 dB input level will produce an increase of 20 dB gain. The....
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Study the Analog to Digital capabilities of Atmel ATtiny26. This tiny but mighty IC is really a miracle. One special thing is the internal 10-inputs multiplexed ADC circuit which can covert analog voltages to bytes. This check circuit uses only 3 inputs. Of....
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The amp was called "El Cheapo 2-30", and was rated at a maximum of 30W per channel into 16 Ohms. It used a single regulated power supply and capacitor coupled speaker. Having a scan of the original, I can now reproduce the exact circuit details. It was a....
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This small amplifier circuit is ideal for boosting small audio units...
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Here is a nice little receiver for narrow-band FM reception. It can also be used to receive FSK, RTTY and PACKET signals from the HF bands. Basic receiver sensitivity is in the region of 1uV PD and the receiver can be tuned to almost any frequency from....
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Simple construction, reliable operation, very small power consumption, and, most of all, small size. I started with CMOS logic gates, but was soon forced to abandon the concept after a few unsuccessful (and far too complicated) attempts. Then I suddenly....
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Two soft start power supplies. The output voltage slowly increases to the desired output..
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How many times have you wished that there was a simple way to turn on that sub-woofer or some other piece of audio equipment, simply by sending it a signal? This ability is fairly common in commercial subs and some other gear, but there seems to be a....
-
Up to 10 A continuous output current, or operation with 50 % ESD and 18 A peak current are possible without a fan if sufficient natural air flow is present and the ambient temperature does not exceed 30 °C. A small CPU fan (40 x 40 mm) should be used for....
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Most of the ideas in this chapter can be found on the pages of this website, but just in case you want to go over the capabilities of the `508A, we have brought them together. Quite often when you are programming, the first thing you will run out of is....
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By using a low-cost RS-170 camera and this circuit, a voltage that trades the position of an object in ..
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This is a 1-amp variable-voltage PSU. It adjusts from about 3v to 24v: and has the added feature that you can limit the maximum output current. This is invaluable when (for example) you power-up a project for the first time or soak-test a piece of equipment...
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Your 5x7 display is my favourite toy; the tunes and graphics in the elevator display always impress my mates!
Since building the display I developed my own 400 dot matrix using a pic and the SN74154 [4bit binary to 1 of 16 demultiplexer\counter] - in place....
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The idea is simply to turn off the negative voltage load. Some examples:-
- Bias votlages for LCD panels
- RF Amplifiers
- Audio Amplifiers
The good thing about this design is that i can make use of the system i/o voltage to control the on/off and this....
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This is a High Voltage switching device for driving coils and which have big impedance when it is switched off. It can be use in Back-EMF energy recovery tests, Newman coils electronic commutator.....This device is drived by an opto-coupler and can be easily....
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The particular circuit is substantially a generator of accidental numbers, from 1 until the 6. The clue him we see in a line from led, that each one corresponds also in a number from the 1-6, if push and leave, the S1 (push button). This movement corresponds....
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A small circuit that can find a lot applications of measurement time. She has the possibility us inform with sound signal from the BZ1. At the same time, exist the possibility drive a external circuit via the optocoupler IC2, after we connect the applicable....
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Using a modified equal-element design for a lumped-circuit lowpass filter has several advantages over the well-known equal-element design (Reference 1 and Reference 2). The modified design exhibits superior passband performance with only modest degradation....
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This circuit toggles on and off a NE555 with a single momentary switch. Unlike a mechanical bistable relay the circuit backs to the start condition if you switch off the power supply. No relay contact is used...
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Transistors are used for current sources. Base drive for these transistors is derived from the main power supply VA, so that their collector current is proportional to the rail voltage. This feature holds the voltage on the cliff-amp collectors close to....
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The EQ-2 it is a circuit of graphic equalizer 6 band of regulation. Each band is regulated from the potesometers RV1-6, that are, for better optical indicate of regulations, Fader. This does not mean that we cannot him replace with simply potesometer. In the....
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The electronic diagram of the monophonic FM receiver made with TDA7088T is shown on Pic.4.12. If built with SMD components it can be placed in a matchbox, altogether with two button-type batteries. The operating principle of this device is given in the....
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This is a very simple circuit utilising a 555 timer IC to generate square wave of frequency that can be adjusted by a potentiometer.
With values given the frequency can be adjusted from a few Hz to several Khz.
To get very low frequencies replace the....
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This simple circuit is sure to have the police beating a path to your door - however, it has the added advantage of alerting you to their presence even before their footsteps fall on the doormat...
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The input transformer is likely to be the most expensive part of the entire project. As an alternative, a couple of 12 Volt car batteries could be used. The input voltage to the regulator must be at least several volts higher than the output voltage (12V) so....
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This board layout was created using the SOIC version of a PIC16F627A without drawing the usual schematic first. Most of the part values are etched on the Layout. The SIP resistor packs I used are 10k ohm, some experimentation with this value may be....
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This device consists of a ring detector connected to the telephone line. When the telephone rings, the ring detector impresses high-frequency pulses on the ac power line...
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Ql is a pnp power transistor used in conjunction with a ferrite transformer to form a blocking-type oscillator. This oscillator is a fixed- frequency type, and the feedback to sustain oscillations is from capacitor CI. Because of the turns ratio of Tl, the....
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The IR2166 Demo Board is a high efficiency, high power factor, fixed output electronic ballast designed
for driving rapid start fluorescent lamp types. The design contains an EMI filter, active power factor
correction and a ballast control circuit using....
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This circuit is a double direction flash. Similar to Digital Ping- Pong 1, there is a movement of a lit dot, up and down along the LED's length. When the D16 lit the situation changes and there is a reverse movement. Lit D15-14 ??D16, is lit making circles....
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The noise limiter circuit has a preamplifier clipper, and a switchable audio bandpass filter. Audio levels in the 5- to 50-mV range are amplified in a preamp to several volts p-p, fed to a clipper, voice band filter, ..
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This op amp offers a straightforward method of developing a single-polarity stable voltage source (see the figure). TVansi..
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The circuit will accept a video signal, separate the sync pulses, invert the video, and add new video to the old sync pulses. The video signal is brought in through Jl and applied to a clamping circuit consisting of Cl, Dl, D2,D3, Rl, and R2. The clamp....
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It's very simple actually. The idea is that we use what we have learned from the capacitor tests to create a circuit that uses the capacitors to run the load and then by discharging the 1/2 full capacitor into a DC-DC converter we can recharge the initial....
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This counter uses a four-digit display, but with a flip of the range switch, it can display frequencies from 1 to 40 MHz, with a resolution of 100Hz. The MM74C926 CMOS IC contains a four-digit decimal counter that can latch a given count and then use this....
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This general-purpose low-power (5 W) audio amplifier is suitable for driving a spe..
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This is an image Schematic. No Description available...
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The circuit has a frequency response ranging from 100 Hz to 3 MHz; gain is about 30 dB. Field-effect transistor Ql is configured in the common-source self-biased mode; optional resistor Rl sets the input impedance to any desired value. Commonly, it will be....
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I made the power supply which makes about +30V with +5V power supply.
The direct current is changed into the alternating current by the oscillator which used the schmitt trigger inverter which has the hysteresis characteristic and the resonance circuit. The....
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A TMOS power FET, Ql, and an LM393 comparator provide a high-efficiency rectifier circuit. When V,. exceeds V,, Ul"s output becomes high and Ql conducts. Conversely, when VB exceeds V,., the comparator output becomes low and Ql does not conduct. The....
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The monitor senses an ajar door and, if the situation isn"t corrected within 20 seconds, sounds a beeping alarm. The circuit is controlled by a magnetic reed switch and magnet on the door. With the door closed, the switch is closed and the alarm is....
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The circuit uses the exceptionally low input current (O.lpA) of the CA3420 BiMOS op amp. With only a single 10 megohm resistor, the circuit covers the range from ±50 pA maximum to a full-scale sensitivity of ±1.5 pA.
..
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This project displays telephone numbers decoded from tones. A microphone picks up the tones, a preamplifier boosts the signals, an SSI-202 DTMF chip decodes the tones, a Basic Stamp acts as an interface to an LCD display and also provides "RS-232" serial....
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The ac ringing voltage (typically 40 to 90 V at 26 Hz) is rectified by U1, the tone-ringer IC, and is used to drive ..
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A bridge rectifier and 12-volt regulator powers the MOSFET sensing circuit. The unregulated output of the bridge rectifier operates the drain solenoid via switch SI. The sensor itself is built from two electrodes, one made of copper, the other of lead. In....
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Whoever thinks about reproducing an interface for the Aladin, should first of all be aware of the fact that there are two different versions of the interface. The first version, easier to assemble, enables the user to transfer dive data from the Aladin to....
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This circuit turns on the brake lights of a parked car when the headlights of an oncoming car are detected, wa..
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A variable Wien bridge provides frequency tuning from 20 Hz to 20kHz. Gain control comes from the positive temperature coefficient of the lamp. When power is applied, the lamp is at a low resistance value, the gain is high, and oscillation amplitude....
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The dc values of op-amp offsets can`t always be taken for granted when delivering ac outputs. No device is ever exactly symmetrical for maximum positive slew rate versus maximum negative slew rate. Consequently, there is always some range of output slew....
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That circuit protects the overdriven signals going into an amplifier.
Instead of a zener diode we use a transistor.
That way we ensure that the above the ordinary input voltages ( 1 volt r.m.s.) can be acheaved without distortion.
Also the use of a....
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These two simple circuits provide zero voltage switching. They can be used with full wave bridges or in antiparallel to provide full wave control and are normally used to trigger power thyristors. If an input signal is present during the time the ac voltage....
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The converter generates an output voltage which is linearly proportional to the input frequency waveform. Each zero crossing at the comparator"s input causes a precise amount of change to be dispensed into the op amp"s summing junction. This charge in turn....
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Portable systems often include circuitry that derives power from an external source, such as USB. When the system disconnects from the USB supply, a battery takes over and supplies current via a dc/dc converter. A diode-OR connection (Figure 1 offers the....
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The circuit in Figure 1 accommodates lower cutoff frequencies without sacrificing the step-response time. A window comparator monitors the delta (difference) between the filter's input and output. When the delta exceeds ±50 mV, the filter increases its slew....
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You can use this powerfull amplifier in any small audio project. It is very small (6.5 x 4.5 cm).It outputs 10W and uses a 9V battery...
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This simple audio power amplifier was originally designed for a circuit board workshop, conducted by the OSU IEEE Student Group. At the workshop, 20 participants each constructed this amplifier, by etching and drilling the single sided circuit board,....
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This circuit generates sinusoidal, square, and triangle waveforms simultaneously. Set the frequency to a particular value or vary it, as-shown above. An op amp can be added for extra drive capability and simplified amplitude adjustment. ..
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This unit delivers 0 to 20 volts at up to 4 amps in 0.1 volt increments. The entire device runs on a PIC16F870 (about $3 in small quantities). This is basically a switching power supply with the voltage regulation done in software. The PIC used here has....
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A fixed current flows through any load that is connected between the positive supply and Ql"s collector. The noninverting..
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This circuit passes the input signal at unity gain, either unchanged or inverted, depending on the digital control input. A buffered input is shown, since low-source impedance is essential. Gain can be added by modifications to the feedback networks.....
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For checking resonances, tuned circuits, antennas, etc., this circuit covers the 2-to 20-MHz range. Ql serves a..
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The working principle of this cheap and easy to build metal detector circuit consists in mixing two equal frequencies which causes a low-frequency interference. When one of the oscillators become unstable then the frenquency of the interference will be....
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Its a very easy interface to build an requires only a few £/$ worth of components. A you can see by the picture on the right, there`s not much to it. To be honest, the pictur is misleading. This hamcomm interface has an added `extra` facility. The original....
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NOTE: FOR BRIDGE CONFIGURATION: t install jumpers ju2 and ju4 2.remove j 1)3 3.remove rio 4replace ..
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This circuit is often used by amateur radio operations, shortwave listeners, and other operators of shortwave receivers to calibrate the dial pointer. The oscillator operates at a fundamental frequency of 100 kHz, and the harmonics are used to locate points....
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Despite exhaustive searching, every reasonably priced solenoid valve for controlling propane during pushbutton start required 12VDC, beyond the capabilities of a normal pump battery. I know that there are methods to generate HV pulses which will actuate the....
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This switch uses four CD4013 BE dual flip-flops, an inverter, and an optoisolator to drive a triac. The circuit can switch 25-A ac load current. A standard 4x3 telephone keyboard is used to enter a 6-digit code. In case of a wrong code, a signal is....
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This cross fader circuit can be used for fading between two slide projectors. As R3 is moved to either side of center, one triac is fired earlier in each half cycle, and the other iater.
..
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The MAX420 is operated at a gain of 191 to convert the 52 p.VI o C output of the type J thermocouple to a 10 mV/°C signal. The -2.2 mV/°C tempco of the 2N3904 is added into the summing junction with a gain of 42.2 to provide cold-junction....
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Adding an unity-gain buffer to your analog circuit can increase its precision. For example, by itself, the op a..
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This simple PC Smartcard reader was shown in Electronics Design magazine February 17, 1997 issue on page 172 in the ideas for design section. The circuit is designed by Jose Carlos Cossio and is based on simple smartcard reader design shown on the same....
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The current tracer helps locate a defective IC that is loading down the power supply. The tracer amplifies the small voltage drop caused by current flow along a fraction of an inch of PC wiring and drives an ordinary microammeter. Needle-point test probes....
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Output-clamp diodes are mandatory because loudspeakers are inductive loads. Output LR isolation is also used because audio amplifiers are usually expected to handle up to 2 µ¥ load capacitance. Large, supply-bypass capacitors located close to the IC are....
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Its based on inductive pickup and very easy to install. Have a look at the pic. (remove LED and connect transistor collector to pin4). I hope it will exactly suits to your tachometer...
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This circuit produces a 20-MHz clock phase locked to a 10-MHz clock present in the Apple MAC II. To generate..
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Capacitor CI charges through resistor Rl, and when the gate level established by potentiometer R2 is high enou..
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A flip of 51 puts the system in action. Power for the circuit is captured from the ignition switch, and circuit receives no power until the ignition switch is closed. When the camera is turned on, the capacitor C1 is charged and the emitter follower....
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The proposed capacitance is a very powerful assembly to measure in 7 ranges
capacitors of 1 pF to 999 uF, avecune excellent precision of about 10 -3 .
The range change is fully automatic. The display shows 3 digits
with decimal point. Three LEDs....
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This is a simple Laser communication system. It can transmit and receive signal from any audio device.Communication distance is few meters. All components are not critical. Transistor 2N2222 may be on the coolrib. Laser diode is from laser pointer...
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Figure 1 shows a method for driving all the LEDs with a single driver IC from Catalyst Semiconductor (www.catsemi.com), the CAT32. Power comes from a single lithium-ion battery cell. A FET switch can independently turn off the group of six LEDs. The shutdown....
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In the circuit the frequency trimming component is arranged so that the voltage across it is in quadrature with the voltage V0 from the bridge so that as it is adjusted the attenuation of the bridge only changes a little, avoiding the need for a two gang....
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Where it really shines is in the univibe. The 'vibe uses a dual section, reverse log taper pot that's just a bit easier to find than a dinosaur's tooth. If we notice that the pot is really wired as two variable resistors, we can use an LED/dual LDR module....
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Half of the effort in this project was to achieve the original timing. When I removed the old coils from the stator poles, I concluded that the timing signal was coming from this pole. The coil that was on this pole had many turns of very fine wire, hardly....
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This is quite a nice chip, and has myriad uses, but we only need it to perform one function here. Since most game systems output the composite sync information along with the NTSC video output, and since most RGB monitors will not accept this extraneous info....
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The dimming action is controlled by varying the amount of current passed through triac Q4 and, thus, the lamp plugged into ac receptacle SOL Unijunction transistor Q3 operates as a relaxation oscillator whose output pulse frequency depends on how fast....
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The circuit board and switches must be protected from the elements. Dampness or condensation will cause malfunction. Without its terminal blocks, the board is small. Ideally, you should try to find a siren with enough spare space inside to accommodate it.....
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High Quality simple design
No need for a preamplifier Can be directly connected to CD players, tuners and tape recorders. Simply add a 10K Log potentiometer (dual gang for stereo) and a switch to cope with the various sources you need...
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This audio amplifier circuit, connected to 32 Ohm impedance mini-earphones, can detect very remote sounds. Useful for theatre, cinema and lecture goers: every word will be clearly heard. You can also listen to your television set at a very low volume,....
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With all the holidays upon us, understandably some of us will be drinking alcoholic beverages. This circuit can be used as a guideline how much you have had to drink and how good your reaction time is. This circuit does not tell you whether you are over the....
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For it`s maximum result, the final stage of the amplifier should have the proper power supply, as the flowing, currents are very high. An Class A amplifier, requires attention. These are the rules for the power supply for the Class A audio amplifier. The....
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This circuit de-energizes a normally energized relay if the input voltage goes above or below two individually set voltages. The transistor driving the relay is normally turned on by R4, so the relay is normally energized. Ifthe cathode of Dl or D2 is....
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This basic oscillator will detect the Earth magnetic field. The ferrite rod and coil are taken from an old Medium Wave receiver and a small magnet is glued at one end. Tune to a medium wave commercial station until you hear a beat note. Any movement of the....
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Two inputs, A and B, control the bridge. With both high (or open circuit) both ends of the motor are connected to 0v. Connect A low and Tr2 turns on causing the motor to go forward. Connect B low and Tr6 turns on, reversing the motor. If A and B are both....
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The battery powered light turns on easily, stays on for just a few seconds, and then turns off again. The circuit is triggered when you place a finger across the gap between two strips of metal, about l/16th inch apart. Enough current will flow through your....
The Gate Boost SE uses a 1381, a 2N7000 MOSFET and a 2N3906 with a unique voltage doubler to increase the voltage applied to the gate of the MOSFET. Normally the 2.6V output of a 1381C is barely able to turn on the 2N7000. As a result the "on....
The circuit is based on a low noise, high gain two stage PNP and NPN transistor amplifier, using DC negative feedback through R6 to stabilize the working conditions quite precisely. Output level is attenuated by P1 but, at the same time, the stage gain is....
This encoder uses a single contact per key keyboard and provides all other switching function electronically. The diode between terminals 8 and 15 prevents the output going more than 1 volt negative with respect to the negative supply V-..
This is a circuit for controlling the speed of small DC motors, it works nicely as a speed controller for an HO or N gauge model railroad...
This circuit uses two transistors and one IC (555 timer IC) to produce a pulsating ultrasonic frequency. Transistors Ql and Q2 are connected in a direct-coupled oscillator. The frequency of that oscillator is set by capacitor CI. The oscillator output is....
The timing must be exact to get those high voltage spikes. I used a tiny magnet on the rotor, that triggered a reedswitch allowing the relay to pulse the energy from the recovery coil to the primary battery. In the same time the rest of the circuit is....
The NE570 can be used to make a high performance compressor FTA, except that the rectifier is connected to the input. This makes gain inversely proportional to the input level so that a drop of 20 dB input level will produce an increase of 20 dB gain. The....
Study the Analog to Digital capabilities of Atmel ATtiny26. This tiny but mighty IC is really a miracle. One special thing is the internal 10-inputs multiplexed ADC circuit which can covert analog voltages to bytes. This check circuit uses only 3 inputs. Of....
The amp was called "El Cheapo 2-30", and was rated at a maximum of 30W per channel into 16 Ohms. It used a single regulated power supply and capacitor coupled speaker. Having a scan of the original, I can now reproduce the exact circuit details. It was a....
This small amplifier circuit is ideal for boosting small audio units...
Here is a nice little receiver for narrow-band FM reception. It can also be used to receive FSK, RTTY and PACKET signals from the HF bands. Basic receiver sensitivity is in the region of 1uV PD and the receiver can be tuned to almost any frequency from....
Simple construction, reliable operation, very small power consumption, and, most of all, small size. I started with CMOS logic gates, but was soon forced to abandon the concept after a few unsuccessful (and far too complicated) attempts. Then I suddenly....
Two soft start power supplies. The output voltage slowly increases to the desired output..
How many times have you wished that there was a simple way to turn on that sub-woofer or some other piece of audio equipment, simply by sending it a signal? This ability is fairly common in commercial subs and some other gear, but there seems to be a....
Up to 10 A continuous output current, or operation with 50 % ESD and 18 A peak current are possible without a fan if sufficient natural air flow is present and the ambient temperature does not exceed 30 °C. A small CPU fan (40 x 40 mm) should be used for....
Most of the ideas in this chapter can be found on the pages of this website, but just in case you want to go over the capabilities of the `508A, we have brought them together. Quite often when you are programming, the first thing you will run out of is....
By using a low-cost RS-170 camera and this circuit, a voltage that trades the position of an object in ..
This is a 1-amp variable-voltage PSU. It adjusts from about 3v to 24v: and has the added feature that you can limit the maximum output current. This is invaluable when (for example) you power-up a project for the first time or soak-test a piece of equipment...
Your 5x7 display is my favourite toy; the tunes and graphics in the elevator display always impress my mates! Since building the display I developed my own 400 dot matrix using a pic and the SN74154 [4bit binary to 1 of 16 demultiplexer\counter] - in place....
The idea is simply to turn off the negative voltage load. Some examples:- - Bias votlages for LCD panels - RF Amplifiers - Audio Amplifiers The good thing about this design is that i can make use of the system i/o voltage to control the on/off and this....
This is a High Voltage switching device for driving coils and which have big impedance when it is switched off. It can be use in Back-EMF energy recovery tests, Newman coils electronic commutator.....This device is drived by an opto-coupler and can be easily....
The particular circuit is substantially a generator of accidental numbers, from 1 until the 6. The clue him we see in a line from led, that each one corresponds also in a number from the 1-6, if push and leave, the S1 (push button). This movement corresponds....
A small circuit that can find a lot applications of measurement time. She has the possibility us inform with sound signal from the BZ1. At the same time, exist the possibility drive a external circuit via the optocoupler IC2, after we connect the applicable....
Using a modified equal-element design for a lumped-circuit lowpass filter has several advantages over the well-known equal-element design (Reference 1 and Reference 2). The modified design exhibits superior passband performance with only modest degradation....
This circuit toggles on and off a NE555 with a single momentary switch. Unlike a mechanical bistable relay the circuit backs to the start condition if you switch off the power supply. No relay contact is used...
Transistors are used for current sources. Base drive for these transistors is derived from the main power supply VA, so that their collector current is proportional to the rail voltage. This feature holds the voltage on the cliff-amp collectors close to....
The EQ-2 it is a circuit of graphic equalizer 6 band of regulation. Each band is regulated from the potesometers RV1-6, that are, for better optical indicate of regulations, Fader. This does not mean that we cannot him replace with simply potesometer. In the....
The electronic diagram of the monophonic FM receiver made with TDA7088T is shown on Pic.4.12. If built with SMD components it can be placed in a matchbox, altogether with two button-type batteries. The operating principle of this device is given in the....
This is a very simple circuit utilising a 555 timer IC to generate square wave of frequency that can be adjusted by a potentiometer. With values given the frequency can be adjusted from a few Hz to several Khz. To get very low frequencies replace the....
This simple circuit is sure to have the police beating a path to your door - however, it has the added advantage of alerting you to their presence even before their footsteps fall on the doormat...
The input transformer is likely to be the most expensive part of the entire project. As an alternative, a couple of 12 Volt car batteries could be used. The input voltage to the regulator must be at least several volts higher than the output voltage (12V) so....
This board layout was created using the SOIC version of a PIC16F627A without drawing the usual schematic first. Most of the part values are etched on the Layout. The SIP resistor packs I used are 10k ohm, some experimentation with this value may be....
This device consists of a ring detector connected to the telephone line. When the telephone rings, the ring detector impresses high-frequency pulses on the ac power line...
Ql is a pnp power transistor used in conjunction with a ferrite transformer to form a blocking-type oscillator. This oscillator is a fixed- frequency type, and the feedback to sustain oscillations is from capacitor CI. Because of the turns ratio of Tl, the....
The IR2166 Demo Board is a high efficiency, high power factor, fixed output electronic ballast designed for driving rapid start fluorescent lamp types. The design contains an EMI filter, active power factor correction and a ballast control circuit using....
This circuit is a double direction flash. Similar to Digital Ping- Pong 1, there is a movement of a lit dot, up and down along the LED's length. When the D16 lit the situation changes and there is a reverse movement. Lit D15-14 ??D16, is lit making circles....
The noise limiter circuit has a preamplifier clipper, and a switchable audio bandpass filter. Audio levels in the 5- to 50-mV range are amplified in a preamp to several volts p-p, fed to a clipper, voice band filter, ..
This op amp offers a straightforward method of developing a single-polarity stable voltage source (see the figure). TVansi..
The circuit will accept a video signal, separate the sync pulses, invert the video, and add new video to the old sync pulses. The video signal is brought in through Jl and applied to a clamping circuit consisting of Cl, Dl, D2,D3, Rl, and R2. The clamp....
It's very simple actually. The idea is that we use what we have learned from the capacitor tests to create a circuit that uses the capacitors to run the load and then by discharging the 1/2 full capacitor into a DC-DC converter we can recharge the initial....
This counter uses a four-digit display, but with a flip of the range switch, it can display frequencies from 1 to 40 MHz, with a resolution of 100Hz. The MM74C926 CMOS IC contains a four-digit decimal counter that can latch a given count and then use this....
This general-purpose low-power (5 W) audio amplifier is suitable for driving a spe..
The circuit has a frequency response ranging from 100 Hz to 3 MHz; gain is about 30 dB. Field-effect transistor Ql is configured in the common-source self-biased mode; optional resistor Rl sets the input impedance to any desired value. Commonly, it will be....
I made the power supply which makes about +30V with +5V power supply. The direct current is changed into the alternating current by the oscillator which used the schmitt trigger inverter which has the hysteresis characteristic and the resonance circuit. The....
A TMOS power FET, Ql, and an LM393 comparator provide a high-efficiency rectifier circuit. When V,. exceeds V,, Ul"s output becomes high and Ql conducts. Conversely, when VB exceeds V,., the comparator output becomes low and Ql does not conduct. The....
The monitor senses an ajar door and, if the situation isn"t corrected within 20 seconds, sounds a beeping alarm. The circuit is controlled by a magnetic reed switch and magnet on the door. With the door closed, the switch is closed and the alarm is....
The circuit uses the exceptionally low input current (O.lpA) of the CA3420 BiMOS op amp. With only a single 10 megohm resistor, the circuit covers the range from ±50 pA maximum to a full-scale sensitivity of ±1.5 pA. ..
This project displays telephone numbers decoded from tones. A microphone picks up the tones, a preamplifier boosts the signals, an SSI-202 DTMF chip decodes the tones, a Basic Stamp acts as an interface to an LCD display and also provides "RS-232" serial....
The ac ringing voltage (typically 40 to 90 V at 26 Hz) is rectified by U1, the tone-ringer IC, and is used to drive ..
A bridge rectifier and 12-volt regulator powers the MOSFET sensing circuit. The unregulated output of the bridge rectifier operates the drain solenoid via switch SI. The sensor itself is built from two electrodes, one made of copper, the other of lead. In....
Whoever thinks about reproducing an interface for the Aladin, should first of all be aware of the fact that there are two different versions of the interface. The first version, easier to assemble, enables the user to transfer dive data from the Aladin to....
This circuit turns on the brake lights of a parked car when the headlights of an oncoming car are detected, wa..
A variable Wien bridge provides frequency tuning from 20 Hz to 20kHz. Gain control comes from the positive temperature coefficient of the lamp. When power is applied, the lamp is at a low resistance value, the gain is high, and oscillation amplitude....
The dc values of op-amp offsets can`t always be taken for granted when delivering ac outputs. No device is ever exactly symmetrical for maximum positive slew rate versus maximum negative slew rate. Consequently, there is always some range of output slew....
That circuit protects the overdriven signals going into an amplifier. Instead of a zener diode we use a transistor. That way we ensure that the above the ordinary input voltages ( 1 volt r.m.s.) can be acheaved without distortion. Also the use of a....
These two simple circuits provide zero voltage switching. They can be used with full wave bridges or in antiparallel to provide full wave control and are normally used to trigger power thyristors. If an input signal is present during the time the ac voltage....
The converter generates an output voltage which is linearly proportional to the input frequency waveform. Each zero crossing at the comparator"s input causes a precise amount of change to be dispensed into the op amp"s summing junction. This charge in turn....
The circuit in Figure 1 accommodates lower cutoff frequencies without sacrificing the step-response time. A window comparator monitors the delta (difference) between the filter's input and output. When the delta exceeds ±50 mV, the filter increases its slew....
You can use this powerfull amplifier in any small audio project. It is very small (6.5 x 4.5 cm).It outputs 10W and uses a 9V battery...
This simple audio power amplifier was originally designed for a circuit board workshop, conducted by the OSU IEEE Student Group. At the workshop, 20 participants each constructed this amplifier, by etching and drilling the single sided circuit board,....
This circuit generates sinusoidal, square, and triangle waveforms simultaneously. Set the frequency to a particular value or vary it, as-shown above. An op amp can be added for extra drive capability and simplified amplitude adjustment. ..
This unit delivers 0 to 20 volts at up to 4 amps in 0.1 volt increments. The entire device runs on a PIC16F870 (about $3 in small quantities). This is basically a switching power supply with the voltage regulation done in software. The PIC used here has....
A fixed current flows through any load that is connected between the positive supply and Ql"s collector. The noninverting..
This circuit passes the input signal at unity gain, either unchanged or inverted, depending on the digital control input. A buffered input is shown, since low-source impedance is essential. Gain can be added by modifications to the feedback networks.....
For checking resonances, tuned circuits, antennas, etc., this circuit covers the 2-to 20-MHz range. Ql serves a..
The working principle of this cheap and easy to build metal detector circuit consists in mixing two equal frequencies which causes a low-frequency interference. When one of the oscillators become unstable then the frenquency of the interference will be....
Its a very easy interface to build an requires only a few £/$ worth of components. A you can see by the picture on the right, there`s not much to it. To be honest, the pictur is misleading. This hamcomm interface has an added `extra` facility. The original....
NOTE: FOR BRIDGE CONFIGURATION: t install jumpers ju2 and ju4 2.remove j 1)3 3.remove rio 4replace ..
This circuit is often used by amateur radio operations, shortwave listeners, and other operators of shortwave receivers to calibrate the dial pointer. The oscillator operates at a fundamental frequency of 100 kHz, and the harmonics are used to locate points....
Despite exhaustive searching, every reasonably priced solenoid valve for controlling propane during pushbutton start required 12VDC, beyond the capabilities of a normal pump battery. I know that there are methods to generate HV pulses which will actuate the....
This switch uses four CD4013 BE dual flip-flops, an inverter, and an optoisolator to drive a triac. The circuit can switch 25-A ac load current. A standard 4x3 telephone keyboard is used to enter a 6-digit code. In case of a wrong code, a signal is....
This cross fader circuit can be used for fading between two slide projectors. As R3 is moved to either side of center, one triac is fired earlier in each half cycle, and the other iater. ..
The MAX420 is operated at a gain of 191 to convert the 52 p.VI o C output of the type J thermocouple to a 10 mV/°C signal. The -2.2 mV/°C tempco of the 2N3904 is added into the summing junction with a gain of 42.2 to provide cold-junction....
Adding an unity-gain buffer to your analog circuit can increase its precision. For example, by itself, the op a..
This simple PC Smartcard reader was shown in Electronics Design magazine February 17, 1997 issue on page 172 in the ideas for design section. The circuit is designed by Jose Carlos Cossio and is based on simple smartcard reader design shown on the same....
The current tracer helps locate a defective IC that is loading down the power supply. The tracer amplifies the small voltage drop caused by current flow along a fraction of an inch of PC wiring and drives an ordinary microammeter. Needle-point test probes....
Output-clamp diodes are mandatory because loudspeakers are inductive loads. Output LR isolation is also used because audio amplifiers are usually expected to handle up to 2 µ¥ load capacitance. Large, supply-bypass capacitors located close to the IC are....
Its based on inductive pickup and very easy to install. Have a look at the pic. (remove LED and connect transistor collector to pin4). I hope it will exactly suits to your tachometer...
This circuit produces a 20-MHz clock phase locked to a 10-MHz clock present in the Apple MAC II. To generate..
Capacitor CI charges through resistor Rl, and when the gate level established by potentiometer R2 is high enou..
A flip of 51 puts the system in action. Power for the circuit is captured from the ignition switch, and circuit receives no power until the ignition switch is closed. When the camera is turned on, the capacitor C1 is charged and the emitter follower....
The proposed capacitance is a very powerful assembly to measure in 7 ranges capacitors of 1 pF to 999 uF, avecune excellent precision of about 10 -3 . The range change is fully automatic. The display shows 3 digits with decimal point. Three LEDs....
This is a simple Laser communication system. It can transmit and receive signal from any audio device.Communication distance is few meters. All components are not critical. Transistor 2N2222 may be on the coolrib. Laser diode is from laser pointer...
In the circuit the frequency trimming component is arranged so that the voltage across it is in quadrature with the voltage V0 from the bridge so that as it is adjusted the attenuation of the bridge only changes a little, avoiding the need for a two gang....
Where it really shines is in the univibe. The 'vibe uses a dual section, reverse log taper pot that's just a bit easier to find than a dinosaur's tooth. If we notice that the pot is really wired as two variable resistors, we can use an LED/dual LDR module....
This is quite a nice chip, and has myriad uses, but we only need it to perform one function here. Since most game systems output the composite sync information along with the NTSC video output, and since most RGB monitors will not accept this extraneous info....
The dimming action is controlled by varying the amount of current passed through triac Q4 and, thus, the lamp plugged into ac receptacle SOL Unijunction transistor Q3 operates as a relaxation oscillator whose output pulse frequency depends on how fast....
The circuit board and switches must be protected from the elements. Dampness or condensation will cause malfunction. Without its terminal blocks, the board is small. Ideally, you should try to find a siren with enough spare space inside to accommodate it.....
High Quality simple design No need for a preamplifier Can be directly connected to CD players, tuners and tape recorders. Simply add a 10K Log potentiometer (dual gang for stereo) and a switch to cope with the various sources you need...
This audio amplifier circuit, connected to 32 Ohm impedance mini-earphones, can detect very remote sounds. Useful for theatre, cinema and lecture goers: every word will be clearly heard. You can also listen to your television set at a very low volume,....
With all the holidays upon us, understandably some of us will be drinking alcoholic beverages. This circuit can be used as a guideline how much you have had to drink and how good your reaction time is. This circuit does not tell you whether you are over the....
For it`s maximum result, the final stage of the amplifier should have the proper power supply, as the flowing, currents are very high. An Class A amplifier, requires attention. These are the rules for the power supply for the Class A audio amplifier. The....
This circuit de-energizes a normally energized relay if the input voltage goes above or below two individually set voltages. The transistor driving the relay is normally turned on by R4, so the relay is normally energized. Ifthe cathode of Dl or D2 is....
This basic oscillator will detect the Earth magnetic field. The ferrite rod and coil are taken from an old Medium Wave receiver and a small magnet is glued at one end. Tune to a medium wave commercial station until you hear a beat note. Any movement of the....
Two inputs, A and B, control the bridge. With both high (or open circuit) both ends of the motor are connected to 0v. Connect A low and Tr2 turns on causing the motor to go forward. Connect B low and Tr6 turns on, reversing the motor. If A and B are both....
The battery powered light turns on easily, stays on for just a few seconds, and then turns off again. The circuit is triggered when you place a finger across the gap between two strips of metal, about l/16th inch apart. Enough current will flow through your....
