Vacuum Tubes Valves
Musical & effects
Yagi Uda Antennas
Metal Detector Circuits
Liquid Sensing Circuits
Light Sensing Circuits
Voltage Detector Circuits
Air-Gas Detection Circuits
Human Sensing Circuits
RF & Radiation
Optical Sensing Circuits
Free Energy Circuits
AC to DC & DC to DC
Solar Cell Circuits
Micro Power Circuits
Switching Power Supplies
Light Laser LED
Digital to Analog
Analog to Digital
Data Bus Circuits
Voltage to Pulse
Current to Voltage
Frequency to Voltage
RF Converter Circuits
Sine to Square Wave
Voltage to Current
voltage to frequency
Period to Voltage
Video Wall circuits
TV Video Circuits
Motor Control Circuits
8051 / 8052
PCB CAD Software
Car bike Circuits
555 Timer Circuits
Remote Control Toy
H Bridge Circuit
Interconnection & Timing
Digital Signal Integrity
Digital & Bipolars
Sensors & Detectors
Regulated Power Supply
4 Band Resistor
5 Band resistor
6 Band resistor
Meter Counter Circuits
Fuel-cell battery tester
This circuit was designed for testing fuel cells, but it could also be used for testing batteries under a constant current load. It provides a dynamic, constant current load, eliminating the need to manually adjust the load to maintain a constant load. For fuel cell application, the load must be able to absorb 20-40 A, and since a single cell...
Continually monitors battery voltage during use and consumes only about 250 ? A (until the end point is reached). Near the end point Trl turns off, allowing Tr2 to illuminate the LED to increase current drain further leading to a distinct turn off point.
Voltage monitor circuit
This circuit gives an early warning of the discharge of batteries. Zener diode Dl is chosen for the voltage below which an indication is required (9 V). Should the supply drop to below 7 V, Dl will cease conducting causing Ql to shut off.
Bargrapk car voltmeter
The LM39X4 acts as a LED-driving vol-tometer that has its basic maximum and minimum readings determined by the values of R2 and RV2. When correctly adjusted, the unit actually covers the 2 volt to 3 volt range, but it is made to read a supply voltage span of 10-10 volts to 15 volts by interposing potential divider R1-RV1 between the supply line...
Suppressed zero meter
A zener diode placed in series with a voltmeter will prevent the meter from reading until the applied voltage exceeds the zener voltage
The sensing circuit rapidly disconnects the battery voltage and load whenever the voltage drops below a preset threshold. One-way operation prevents the circuit from reconnecting the load if the voltage should then rise above the threshold. Cl ensures that the circuit doesn"t activate while making connections to the battery; if you...
When Sl is depressed, Cl begins to charge to the supply voltage. That places a forward bias on the gate of Ql turning it on and supplying current to load resistor RL. When the charge on Clleaks off, the transistor shuts off, cutting off current to the load. That load could be anything from a transistor radio to a child"s toy.
If a NiCad battery is discharged to a point at which the lowest capacity cell becomes fully discharged and reverses polarity, that cell will usually short internally and become unusable. To prevent this type of damage, this circuit detects a one-cell drop of 1.25 V and turns the load off before cell reversal can occur. Low-current zener or other...
Circuit provides a minimum of 7 V until the 9-V battery voltage falls to less than 2 V. When the battery voltage is above 7 V, the MAX630"s IC pin is low, putting it into the shutdown mode which draws only 10 nA. When the battery voltage falls to 7 V, the MAX8212 voltage detector"s output increases. The MAX630 then maintains the output...
Most of the circuitry is contained in the LM3914 dot/bar-graph driver IC chip. In addition to the comparator circuitry within the package, it also contains a stable reference supply and the drivers for the LEDs. Resistor R2 acts as the current limiter for all the LEDs. Resistor R2 may be varied for LED brightness. The unit will illuminate...
Because NiCad batteries maintain a constant output voltage, it is difficult to determine how much of the battery"s charge remains. The circuit provides a way of determining the capacity of a battery by draining it at a preset current to its depleted voltage of 1 Vi cell. Measure the discharge time ofthe cells and perform a simple calculation to...
To prevent battery damage due to over -disc barge, a low-voltage detector and switch should be included in the design of the battery backup circuit. The detector circuit should consume extremely low current. The switch should exlnbit a low-voltage drop and be easy to control. R1 and D2 provide a trickle charge for the battery. Chosen for its low...
NiCad batteries are excellent rechargeable power sources for portable equipment, but ~care must be taken to ensure that the batteries are not damaged by overdischarge. Specifically, a NiCad battery should not be discharged to the point where the polarity of the cell is reversed and is reverse-charged by the higher-capacity cells. This reverse...
The test circuit gives an indication of the capacity remaining in a battery. By noting the time in seconds that the LED remains on after you depress the test switch Sl. The circuit has proven reliable in testing NiCad-, carbon-, and alkaline-type batteries. Closing Sl activates the circuit by applying voltage from the battery under test.
A common need in many systems is to obtain positive and negative supplies from a single battery. Where current requirements are small, the circuit shown is a simple solution. It provides symmetrical Â± output voltages, both equal to one half the input voltage. The output voltages are referenced to pin 3, output common. If the input voltage...
The battery life and operating cost of an electric vehicle is severely affected by overdischarge of the battery. This circuit provides both warning and shutdown. An electronic switch is placed in series with the propulsion motor contactor coil. Three modes of operation are possible: When the propulsion power pack voltage is above the 63-V...
A tricolor LED, acts as the visual indicator of the voltage level. The voltage to be measured is connected to the two comparators in parallel. The first 20-KO trimmer defines a voltage between Â±5 V and this becomes the full-scale value of the reference voltage. The second trimmer is a fine adjustment to give any reference voltage between 0 V...
Any potential from 1 to 15 V can be monitored with this circuit. Two lamps alert any undesirable variation. The voltage differential from lamp tum-on to tum-off is about 0.2 Vat any setting. High and low set points are independent of each other. The SCRs used in the circuit should be the sensitive gate type. R3 must be experimentally...
This voltmeter exploits a number of tbe CA3160 BiMOS op amp"s useful characteristics. The available voltage ranges from 10 mV to 300 V. Powered by a single 8.4-V mercury battery, this circuit, with zero input, consumes approximately 500 p,A.
This de voltmeter, with high input resistance, uses a CA3130 BiMOS op amp and measures voltages from 10 m V to 300 V. Resistors R12 and Rl4 are used individually to calibrate tbe meter for full:scale deflection.
A2N3819 FETprovides a solid-state VOM. The 2N3819 acts as a cathode follower in a VOM. The bias offset (meter null) is obtained with R14 and R12 sets full-scale calibration. R2 through R9 should total about 10 MO.
This schematic shows a peak-reading diode voltmeter driven by two stages of amplification. A 100-ILF capacitor provides a fairly large time constant, which results in satisfactory meter damping. The limited differential output voltage coupled with an overdamped meter prevents most needle pinning when you select an incorrect range position, or...
If the battery voltage exceeds about 11 V, current flows through R1, D1, and R2. The voltage produced as a result of current flow through R2 is sufficient to bias transistor Q1 into conduction. That places the collector voltage of Q1 virtually at ground. Therefore, Q2, driven from the collector of Q1, is cut off, LED1 and current-limiting...
Capacitor C4 couples the output of U1 to a simple attenuator, which is used to provide a loss of 0 dB, 20 dB, or 40 dB, depending on the setting of range switch Sl. The circuits sensitivity is 10-V rms for fullscale deflection, so the attenuator gives additional ranges of 100-mV and 1-V rms. The attenuator output is connected through...
Input terminal VIN is connected to the +V line of tbe circuit that the indicator is to monitor, and the grounds of botb circuits are connected togetber. The position of potentiometer Rl"s wiper determines Q1"s base voltage. As long as the transistor gets enough bias voltage to remain on, the low voltage at tbe collector will keep the SCR...
This circuit uses only one JC, either 1, LM393 dual comparator or 1/z, LM339 quad comparator. RV1 and RV3 set the full scale reference voltage, and RV2 and RV4 set the switching thresholds to a value between 0 V and the full-scale reference.
This circuit will allow a multimeter to display the positive or negative peaks of an incoming signal. A 741, JC1, is used in the noninverting mode with R1 defining the input impedance. D1 or D2 will conduct on a positive or negative peak, charging C2 until the inverting input is at the same de level as the incoming peak. This level will...
This current source has continuous control of the magnitude and polarity of its amplifier gain and needs only one voltage reference. The circuit includes reference ~, voltage-amplifier circuit A1 with gainsetting resistor Rs, and bootstrap-follower amplifier A2. The bootstrapping converts the circuit to a current source and allows the load to...
This circuit shows a simple method of achieving a voltage reference which can be trimmed using an 8bit DAC with an on-chip voltage reference. The analogue output from the DAC drives the trim pin of the ZNREF025 via a resistor, R,. When Rs = 0, this circuit will produce a trim range exceeding Â± 5% of the nominal reference voltage. When Rs is...
Digital Led Voltmeter
The voltage to be measured is digitized in an analog-to-digital (A/D) converter and then displayed in three decimal d
The current range in multimeters, particularly the more inexpensive ones, is restricted by the load limits of the internal
Latching Continuity Checker
This circuit detects brief shorts or opens. When S2 is in the up position, the circuit indicates if there is or
Frequency Meter Circuits
VU Meter Circuits
255W Valve RF Transmitter circuit
This transmitter of 255W is depended on the coils we put at it to work in both the middle and the short waves. The power in the antenna is 255W and includes 4 states. The first consists of the EF80 that works as a COLLPITS CLAPP oscillator. Frequency selection is done in a somewhat unusual way: Instead of the variable capacitor, it uses a...
Arduino DAC Signal Generator project
Once the circuit gets current, all variables are initialized and the loop function is continually running. Initially all LEDs are off and there is no signal at the output. By pressing the signal switch, the first light that shows the most signal is at the output and the D0-D7 terminals give the appropriate signal which, when passing from the...
Recording circuit of phone conversations using PC
This circuit is used to record telephone conversations on your landline telephone. All you will need is this small circuit and subscription of your PC. There are few times when we forget what we said or told us. So we need recording. Sometime, not many years ago, recording of this kind of conversation was done with a small tape recorder. The...
FM Micro-Transmitter Bug Surveillance Circuit
The transmitter we recommend to build is quite simple. It can even be built by a beginner. However, unlike the ease of construction and its small size, it is almost certain that it will impress you with its outstanding performance. Its autonomy is 12-15 hours, with a 9 volt battery and its range is from 100 to 300 meters depending on the...
Construction of 50Watt 8Ω two-way Hi-Fi Speakers
The presented speakers are distinguished for their small dimensions and their extraordinary sound. Our home space is often limited and prohibitive for large speakers. This limitation does not mean that we will stay without high Sound Quality. Its design is simple, low cost and is easy to construct. Speaker types are too many and are designed in...
GSM modem circuit with Wavecom WMOi3
Modems are devices that connect either remote devices to a computer, or two or more computers to each other. Their connection is usually wired. The GSM modem we present is wireless. It can connect two computers, a computer with the internet or even be the central unit for a data acquisition system. Generally the construction is a GSM phone...
1W UHF Linear Amplifier with BLW33
This circuit is an amplifier for small transmitters operating in the UHF band, specifically in the 450-800MHz range. The amplifier works in class A and we used the well-known Philips BLW33 transistor for its manufacture. The construction, although simple, can be said to be quite critical due to the high frequency singularity. To achieve this, a...
8W Amplifier with TDA2003 circuit
Many times a small amplifier is needed to meet the needs of small spaces. This amplifier can be either mono or stereo, with this circuitry you can comfortably drive two small speakers. To build the amplifier you do not need anything but a few materials and a small power supply. The power of the amplifier, although low power, will solve many...
FM Linear Amplifier 400mW
This amplifier is intended for amplifying low signals from oscillators in the FM band. It does not have frequency regulators with variable capacitors and coils, it has a wide range and moderate power capable of driving several linear amplifiers. The whole construction is based on the two low-power 2N4427 transistors, which are designed for the...
Digital Signal Integrity
Interconnection and Timing of Digital Circuits
CMOS Circuits Tutorial
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Measuring a Low Ground Resistance Is Key to a Proper Ground System
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Wipers And Tach Problem
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Wizard of Woz: Eleven Things You Might Not Know about Steve Wozniak
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Fuel Pump Problem On My 1987 Foxbody
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