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8051 / 8052
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Remote Control Toy
H Bridge Circuit
Interconnection & Timing
Digital Signal Integrity
Digital & Bipolars
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Regulated Power Supply
4 Band Resistor
5 Band resistor
6 Band resistor
The circuit is a simple rf-actuated switch which will respond to any strong field in the region of the pickup wire. The length of the wire will depend on how much coupling is needed, but a 250-mm length wrapped around the outside of the coaxial cable feeding the antenna should suffice for most power levels. If only one band is used, the wire...
When the digital logic level at the control input is low, the PIN diode is forward-biased by the CMOS gates. The two 1-KO bias resistors limit this current to the PIN diode"s safe forward current limit. In this state, the switch is on. When the control input is high, the diode is reverse-biased and the switch is ~ott. This switch is...
A basic circuit to trigger an SCR is shown in Fig. 67 -lA. This circuit has the disadvantage that the blocking voltage of the photon-coupler output device determines the circuit-blocking voltage, irrespective of higher main SCR capability. Adding capacitor Cl to the circuit, as shown in Fig. 67-lB, will reduce the dV!dt seen by the...
This circuit is effective for lamp and heater loads. Some circuits driving reactive loads require integral cycling and zero-voltage switching-when an identical number of positive and negative half cycles of voltage are applied to the load during a power period. The circuit, although not strictly a relay because of the three-terminal power...
Snubber circuit R2C2, as shown, might be necessary since Rl and Cl are tailored for optimized triggering and not for dV!dt protection. Fiber-optic pairs can be used with discrete SCRs to switch thousands of volts. A photon coupler with a transistor output will limit the trigger-pulse amplitude and rise time because of CTR and saturation...
Since standard CMOS logic operates down to 3-V supply voltages and is specified as low as 30 p.A maximum current sinking/sourcing capability, it is necessary to use a buffer transistor to provide the required current to the IRED if CMOS is to drive the optocoupler. As in the case of the low output TTL families, the H74A output can drive a...
Detection of line-current flow and indicating the flow to an electrically remote point is required in line status monitoring at a variety of points in theJelephone system and auxiliary systems. The line should be minimally unbalanced or loaded by the monitor circuit, and relatively high levels of 60-Hz induced voltages must be ignored. The...
For higher speed applications, up to 1-MHz NRZ, the Schmitt-trigger output HllL series optoisolator provides many features. The 1.6-mA drive current allows fan-in circuitry to drive the IRED,
Al and A2 are two sections of a quad comparator. The first, Al, functions as an amplifier and detector. Resistors R~and R6 set the gain at 100; the output of Al is an open collector to negative-peak-rectify the output with a decay time constant determined by R9 and C3. This de output is then compared with the reference level selected by RB.
This rf power switch operates at 1. 7 MHz with a 50-V source and load. Its on loss is 0.2 dB and its off isolation is 30 dB. It provides 40-W PEP, 45 VrEAK and 0.9 APEAKÂ· The control input can come from CMOS, TTL, LS, etc.,
TTL inverter 74LS14 has an internal 16-Kohm, pull-up resistor that pulls the gate input high when the switch is open. As you close the switch, the 4.7uF capacitor discharges on the first contact. If the switch contacts bounce open, the internal resistor limits the capacitor"s recharge to a rate sufficiently slow to prevent an undesired gate...
This circuit provides the tum-on characteristics of an SCR, but turns off with ease. The switch is comprised of three transistors with descending current ratings: Q3 has a high-current rating and Q2 has a medium rating. The current, !1, to be switched is 15 A.
Using four diode in an array allows using only one MOSPOWER transistor for analog switching. The current flow is controlled by keeping the source-base connection of the MOSFET towards the load. Be sure to use diodes capable of handling the load current and a transistor whose breakdown voltage specification exceeds the peak analog voltage...
Each time the switch closes, the voltage on Cl causes inverter A to change state, with positive feedback from inverter B. Resistor Rl delays the charging and discharging of Cl, making the circuit virtually immune to contact bounce. The circuit works with either CMOS or TTL gates. The values of R1 and C1 are not critical and can be...
A single op amp-one of four contained in the popular LM324-is operating in a variable pulsewidth, free-running squarewave oscillator circuit, with its timed output driving two transistors that control the on/ off cycle of the tape-drive motor. The Dscillator" s positive feedback path holds the secret to the successful operation of the...
A sensitive electret microphone picks up the sound and feeds the signal to a two-stage amplifier circuit, consisting of Ula and Ulb. The amplified output of Ulb is fed Â·to a voltage-doubler circuit (comprised of Dl, D2, C4, and C5). The output of the doubler is input to the gate of Ql.
This circuit can cause a cassette recorder to automatically tum on and record when a sound or noise is present. Another use, is when the sound-activated switch is used to tum on a cassette player so that it operates as a burglar-alarm detector and sounder. Op amps Ula and Ulb are connected in tandem to amplify the sounds picked up by the...
Battery-Saving Disconnect Switch
At a predetermined level of declining terminal voltage, the circuit disconnects the battery from the load
Switch Debouncer With Auto Repeat
This circuit produces an output pulse when SW1 (pushbutton) is depressed. It also becomes a hysteresis ga
Child-Proof Reset Switch
The reset switch on a computer is very important. If an operating instruction threatens to wreck the internal mana
Flip-Flop Debouncer Switch
Although this circuit uses a 74HC74, any CMOS variant of this flip-flop will work. IC1A acts as a true/ compleme
Universal Power Controller
Relay K1 has a low-impedance coil and K2 has a high-impedance coil. When a sensor opens, current is routed throu
This circuit provides either latched switching or timed switching. U1A and UlB provide audio amplification from the
This sound-operated switch will sense the ring of the phone and translate this to a lamp that will go on and off. The
This single-chip circuit adjusts its audio gain according to the ambient noise picked up by the microphone. When
This circuit is a two-channel baseband video switcher. Buffer amps Ul/Ql, U4/Q4, and associated components produce a b
Precision Narrow-Band Tone Switch
This signal tracker and lock detector combine to make a precision tone switch. Filter R3/R4/C2 determines
Satellite Tv Audio Switcher
Some channels offer a separate audio mode (SAP) in a second language. It is usually transmitted on 6.8 MHz, whi
This switching circuit acts like a bank of interlocked mechanical switches; pushing one of the buttons latches its corres
Inexpensive Vhf/Uhf Diode Rf Switch
This circuit uses low-cost IN4148 diodes and exhibits about 1.5 dB insertion loss from 10 to 1000 MHz w
Transistor Turns Op Amp On Or Off
When transistor Q1 is switched off, the circuit behaves as a voltage follower. By applying a positive vol
Touch Switch I
This switch reacts to the touch of a finger to turn lights and/or appliances on or off. The device uses the human body as an
555 Timer Circuits
RC Model Toy Circuits
H Bridge Circuits
Ultrasonic distance finder circuit
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is measured. There are three main categories of distance measurement methods in use: a) By...
Simple Metal detector circuit with CD4030
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to find something potentially valuable, hidden a few centimeters below the soil. So many...
Fully automatic watering circuit for flower pots
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This circuit comes as a solution to this problem. Depending on humidity of the pot at...
Simple deep searching metal detector circuit
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the circuit of this metal detector, it is possible to detect a metal coin in depth of 90 to...
Sub-Harmonic Bass Converter for Electric Guitars
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound, such as filtering or distortion. Instead, a frequency division system produces outputs...
Echo Depth Sounding Sonar for Boats
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the calibration of the rope. This arrangement still exists in some yachts. The big...
100W HiFi Audio Amplifier Circuit
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power supply must be symmetrical so that no electrolytic capacitors are needed at the outlet....
Plant-Pot Water Level Indicator Circuit
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower. The circuit of the device is shown in Figure 2. The water detection is made from the bottom...
Analogue Sound Preasure dB-Meter Circuit
The best human ear can capture sounds from 20Hz to 20KHz. These limits are known to be the broadest that can exist. Normally the normal limits range from 100Hz to about 13KHz and depend on the age and health of the individual. We for our measurements and to have a good accuracy we will get the limits of 20Hz to 20KHz. A sound to be heard does...
Digital Signal Integrity
Interconnection and Timing of Digital Circuits
CMOS Circuits Tutorial