Top Circuits Page 25
- Page 25
-
The purpose of the circuit is to hold the peak of the input voltage on capacitor Cl, and read the value, V0, at the output of U2. Op amps Ul and U2 are connected as voltage followers. When a signal is applied to Vj, Cl will charge to this same voltage....
-
-
The SN75604, with input control logic but requiring only one supply rail, can be used in the "lights on" sensor and alarm driver. The device Vqq and enable inputs are connected to a voltage lead from the light switch. The direction control input is connected....
-
The circuit is used to indicate two different water temperature trip points by turning on LEDs when the temperatures are reached. The circuit is constructed around the LM2904 dual operational amplifier powered from the 12 V auto system. The thermistor is in....
-
The circuit warns car drivers when the air temperature close to the ground approaches 0°C, thereby indicating possible formation of ice on the road surface. Op amp A1 is wired as a voltage level sensor. Op amp A2 is wired as an astable multivibrator which,....
-
The Digi-Tach contains a master-clock circuits (U6)v latch and reset pulse generators (U2-b-U2-d), input signal bonditioner (Ul, U2-a), pulse counter (U3), display and display drivers (DIS1, DIS2, U4, and U5), and a voltage regulator (U7)...
-
A PC usually requires a plug-in ADC card to process analog signals. However, with the circuitry in Figure 1, a PC can communicate with an 18-bit ADC through its serial port. The port provides both positive and negative power supplies as well as control....
-
-
Here is a circuit for using the printer port of a PC, for control application using software and some interface hardware. The interface circuit along with the given software can be used with the printer port of any PC for controlling up to eight equipment .....
-
The circuit can be easily built to a small plastic box with telephone connectors in both ends. The circuit takes about 10-20 mA current, so if the circuit is not in use all the time it is best to use batteries. You can also use small wall transformer to....
-
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....
-
This article describes an I-V curve tracer circuit that uses a computer for display and control. The circuit is controlled via the PC parallel port. Software is provided, written in BASIC, to control the measurement and display the results on the monitor.....
-
PC parallel port can be very useful I/O channel for connecting your own circuits to PC. The PC`s parallel port can be used to perform some very amusing hardware interfacing experiments. The port is very easy to use when you first understand some basic....
-
-
Using the simple circuit in Figure 1, you can control the light intensity in your room or work area from your PC. The heart of the circuit is a low-power D/A converter that converts digital words from a computer's parallel port to analog-voltage signals. To....
-
This project was begun as a means to charge and cycle NiCad batteries but has become a versatile tool for experiments requiring either a controlled voltage up to +30V and/or a current of +/- 2.5 Amps. If all you want to do is charge and recycle NiCad....
-
The circuit in Figure 1 controls 32 voltage-output channels from the parallel port of a PC. The circuit comprises eight DAC7615 quad voltage-output, serial-data programmable, 12-bit DACs. The controlling PC individually programs each of the 32 DAC channels,....
-
The Dallas Semiconductor (www.dalsemi.com) DS1722 digital thermometer allows measurement resolution as fine as 0.0625°C in digital form and with linear response. The accuracy specification is only 2°C, but you can improve this figure by careful calibration.....
-
You can use the parallel port of your PC and a few additional components to generate a powerful, easy-to-use arbitrary-waveform generator. By using a Visual Basic program with the circuit in Figure 1, you can generate any waveform (for example, sinusoid,....
-
This is a very easy and fun to build project that will allow you to control up to eight external devices through your computer`s parallel port. You may for instance control different appliances such as lamps, computers, printers, tv sets, radios, music....
-
Differential multiplexers are generally used in process control applications to eliminate errors due to common mode signals. In this circuit however, advantage is taken of the dual multiplexing capability of the switch. This is achieved by using the....
-
a low cost, high-speed monolithic analog multiplexer. The system works as follows: Selects a channel and initiates a conversion at G = 1 and then looks at the MSB of the conversion result. If the MSB = 1, the ?? will store the value. If the MSB = 0, the ??....
-
When computer peripheral equipment is interfaced, it is convenient to work with logic signal levels. With a nominal 4 V at the output dropping to - 0.6 V on illumination, this circuit reflects the requirements of a high-speed, paper tape optical reader....
-
Anyway, Fluffy is a SX programmer for people who have already experimented with PIC chips, and want to try out the Scenix SX family. I built Fluffy because I wanted to experiment with the SX's, but didn't want to spend $300 or so bucks on the official....
-
The preamplifier is protected from excessive input signals of either polarity by the 2N5909 junction field-effect transistor. A nulling circuit makes it possible to set the preamplifier output voltage to zero at a fixed low level (up to + 10~8A) of the input....
-
The circuit utilizes CA3160 and CA3140 BiMOS op amps to provide a full-scale meter deflection of ± 3 pA. The CA3140 serves as an 1T0 gain stage to provide the required plus and minus output swing for the meter and feedback network. ..
-
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.
..
-
The circuit consists of two basic circuits, the oscillator and the detector. The oscillator uses an FET in a Colpitts configuration. The energy circulating in the oscillator tank is coupled through C4 to the detector circuit, where a small diode (D2)....
-
The circuit uses two general-purpose npn transistors, Ql and Q2, and a special hand-wound, dual-coil probe ferrets out the magnetism. Ql and its associated components form a simple VLF oscillator circuit, with LI, C2, and C3 setting the frequency. The VLF....
-
A simple tester can be used for routine checks for resistance on production lines of relays, coils, or similar components where frequent changes in resistance to be tested are not required. The tester is built around a single quad op amp chip, the LM324. R,....
-
The pitch of the tone is dependent upon the resistance under test. The tester will respond to resistance of hundreds of kilohms, yet it is possible to distinguish differences of just a few tens of ohms in low-resistance circuits. Ql and Q2 form a....
-
A bubble vial with external aluminum-foil electrodes is the sensing element for a simple indicating tiltmeter. To measure bubble displacement, a bridge circuit detects the difference in capacitance between the two sensing electrodes and the reference....
-
The device is a dc switch that is normally on via the forward biasing of Ql via R3. Ql now clamps Q2 into a forward state by biasing its complement well into a saturated state via R4. The dc switch is turned off via a negative voltage above that of the zener....
-
A small neon lamp is triggered into conduction by the telephone's ringing voltage, passes just enough current to activate the LED in optocoupler Ul, which in turn triggers the 6-A Triac that controls 12—a 117-Vac lamp or bell. (Capacitor Cl is necessary....
-
The heart of the circuit is IC1, General Instrument's AY-3-1350 melody-synthesizer IC. IC2 is a TCM1512 telephone ring detector IC that is powered by the telephone line. The circuit's operation begins when IC2 senses a ring pulse on the telephone line. The....
-
A 2N5777 photo-Darlington cell picks up blinking light from the transparent plastic buttons. The power is switched ON and OFF by a hi-beta 2N3904 transistor. The circuit's 9 V battery can be left continuously connected. Less than a micro-ampere is drawn-even....
-
This circuit functions as a line-current sensor and can be connected in series with either of the phone lines. For the circuit to indicate an "in use" status for all phones on a single line, it must be connected in series with the phone line before, or ahead....
-
As you can see, there is only one regulated 12 volt supply operating the entire circuit. I was able to do this simply by AC coupling the received signal to U3 via C10. This allowed me to adjust the offset within an operating window. By using a tantalum....
-
Locator uses a transistor radio as the de-tector. With the radio tuned to a weak station, adjust Cl so the locator oscillator beats against the received signal. When the search head pas¬ses over metal, the inductance of LI changes thereby changing the....
-
When the soil is moist, the LED glows. If the moisture falls below a certain predetermined level, the LED begins to flash. If there is still less moisture, the LED turns off. To calibrate, connect the battery and insert the probe into a container of dry....
-
When the 14B-12B pair opens, 12B is connected to Al's summing point via 13B. The sensor now discharges into the summing point through the 1 µ capacitor. Since the charge voltage is fixed, the average current into the summing point is determined by the....
-
The laser light detector utilizes a sensitive photo transistor (Q5) placed at the focal point of a lens (LE2). The output of Q5 is fed to a sensitive amplifier consisting of array (Al) and is biased via the voltage divider consisting of R14 and Rl. The base....
-
A cadmium sulfide photocell (LDR1, which is a light-dependent resistor) is connected to the base and collector of an npn transistor, Ql. When light hits LDR1, the internal resistance goes from a very high (dark) value to a low (light) value, supplying base....
-
The circuit is light seeking; it will follow a flashlight around a darkened room. A pair of photocells determine the direction in which the robot will move. Each photocell is connected to an op amp configured as a comparator. When sufficient light falls on....
-
M1 is a stepper taken from an old disk drive. There are five pins, i.e., common, coil 1, 2, 3 and 4. Resistance measured between common pin and each coil is about 75 Ohms. Driving current for each coil is then needed about 60mA at +5V supply. A darlington....
-
Some applications may not need user display and key interface, dump terminal is an alternative way for program setting, displaying user interfacing command.Debugging, dump terminal connects with serial port, use only 2-i/o pin, P3.0 for Rxd and P3.1 for Txd.....
-
This circuit was designed to control a 32 channel Christmas light show from the PC serial port. Originally designed with TTL logic, it has been simplified using CMOS circuits to reduce component count. It is a fairly simple, reliable circuit that requires....
-
If you are looking at this page, you probably feel like I did when I tried to run a self-powered PIC programmer with my notebook computer. Yes, the serial port was the ultra-low-power type and wouldn`t provide enough current to power the programmer. The....
-
This is a page of analogue interfaces for joysticks. Although these interfaces have been developed for use with 4QD`s controllers they will have plenty of other uses. Also because of the development history, we have printed circuit boards available (either....
-
If you have access to a Lowe HF-225 shortwave receiver, then you might be interested in this page. If you don`t, then you`d probably be better off leaving now. What follows is a project I completed some time ago, which allows the Lowe HF-225 to be controlled....
-
The circuit in Figure 1 is an RS-232/485 converter that uses the transmitted signal itself to control the flow. The circuit uses MAX232 and MAX483 interface circuits, IC1 and IC2 from Maxim Integrated Products (http://www.maxim-ic.com) to convert between the....
-
I got a problem with my notebook, because it has only COM1. My programmer board, Easy-Downloader must use serial port and the application board also needs to communicate via the same serial port. I do remembered I have to swap DB9 connector of both devices....
-
The circuit will operate reliably from below 1 MHz to above 400 MHz. With Vcc = 5 V the output of the second inverter essentially attains a full swing from 0 V to 5 V. Such large logic output levels and broad frequency range capabilities make this oscillator....
-
This circuit has been designed to provide a clearly visible light, formed by 13 high efficiency flashing LEDs arranged in a pseudo-rotating order. Due to low voltage, low drain battery operation and small size, the device is suitable for mounting on bicycles....
-
The first circuit energizes the relay when the light rises above the preset level. The second circuit energizes the relay when the light falls below the preset level. The two circuits are practically identical. The only difference between them is the....
-
The circuit uses a free-running push-pull dc to dc high voltage converter to get the necessary voltage for the laser plasma tube supply. The supply voltage Vc of this converter, is adjusted by a switch-mode power supply in order to keep the load current....
-
This project flashes eight LEDs in an apparently random manner. It uses a 4060 combined counter and display driver IC which is designed for driving 7-segment LED displays. The sequence is not really random because seven of the LEDs would normally be the....
-
A very simple LED flasher circuit. With HT-2014L the circuit produces 1 flash per second and the HT-2014M produces 2 flashes per second...
-
A relaxation oscillator is used to flash an LED in the base circuit. Cl is charged slowly through R1 by the power source, then discharged periodically through R3 and the LED by the UJT.
..
-
The LED is the CSL310L which contains a red LED and a green LED connected back to back and mounted close together in a single moulding. The LED can emit red or^green light by controlling the polarity of the applied voltage and if the polarity is switched at....
-
A simple and effective receiver for actuating garage doors, alarms, warning systems, etc. The SCR, which has a very low trigger current 30 µ is typical—it requires an input power of only 30 juW to activate the relay. A high Q tuned antenna circuit assures....
-
This general purpose signal source serves very well in signal-tracing applications. The output level is variable to more than 1 Vrms into a 50 O load. Almost any crystal in the 1 to 15 MHz range can be used. Ql forms a Colpitis oscillator with the output....
-
A high speed oscillator is possible by combining an MECL 10 crystal oscillator with an MECL III frequency doubler as shown. One section of the MC10101 is connected as a 100 MHz crystal oscillator with the crystal in series with the feedback loop. The LC....
-
The FET input amplifier has fixed bias with source feedback. This provides a very high input impedance with very low capacitance. The FET amplifier drives an emitter follower which, in spite of the fact that it has a low output impedance, feeds a transformer....
-
Digital ICs and opto-isolators provide the drive for this TMOS servo amplifier, resulting in fewer analog circuits and less drift. Fast and consistent turn-on and turn-off characteristics also enable accurate analog output results directly from the digital....
-
The signal from a synchro receiver or a variable resistive cam follower (potentiometer) is boosted by operational amplifier Ul, whose output swing is limited by back-to-back zeners D3 and D4. The signal is then applied to operational amplifiers U2 and U3,....
-
U1A, an op amp, oscillates at the frequency at which the phase shift in the Wien bridge network is exactly zero degrees. Changing bridge component values changes the oscillator frequency. In this circuit, we need change only the two resistors to do this. S1A....
-
L1 is a loop of 10 to 20 turns of insulated wire with a diameter anywhere between 4" to 4'. Oscillator frequency (7 to 30 MHz) shifts substantially when a person comes near or into the loop. This oscillator together with a resonant detector might make a very....
-
This circuit generates simultaneously, a triangle and a square waveform. It is self starting and has no latch up problems. IC1 is an integrator with a slew rate determined by CT and RT and IC2 is a Schmitt trigger. The output of IC1 ramps up and down between....
-
With only three components and a buffer, a line frequency square wave having a 1:1 duty cycle may be derived from the power supply. During the alternate half-cycle, however, A is effectively clamped to - 0.7 V by Dl in the bridge which offsets the forward....
-
This circuit gives a 3 phase square-wave output for a variable speed motor drive. Operation is straightforward, the 4017 counter is synchronously reset after six clock inputs. The she outputs are combined to give the required waveforms. It is interesting to....
-
The current source formed by Ql in conjunction with capacitor Cl set the duration time of the ramp. As the positive dc voltage at the gate is changed, the peak point firing voltage of the PUT is changed, which changes the duration time...
-
A1 and its associated components furnish an amplitude stable sine wave source. All positive feedback path is a Wein bridge, tuned for 1.5 kHz, Ql, the LT1004 reference, and additional components in Al's negative loop unity-gain stabilize the amplifier. Al's....
-
This is the timekeeping test circuit. It includes a one-transistor circuit to switch in the 5V power supply when present and drop back to the 3v battery the rest of the time. That loop of blue wire-wrapping wire is a lariat used to quickly and easily pull....
-
Nowadays the batteries are gaining more and more power, being the only components that fail to provide energy for portable electronic devices. The evolution is rapid, leading manufacturers electronic equipment to attempt to minimize the consumption of their....
-
The governor following is intended to regulate the light intensity incandescent 220 V. The components in a relatively few, which means it can easily be mounted onto a small plate. After the build, we recommend you place it inside the box which is flush....
-
Door open alarms are used chiefly in automotive, industrial, and appliance applications. This type of circuit can sense the opening of a refrigerator door. When the door opens, a triac could be activated to control the inside light. The figure shows a door....
-
A negative pulse at the input is fed via capacitor Cl to the input pin (2) of the IC, Pin 2 is held slightly above its triggering voltage of 1/3 Vcc by the voltage divider comprising Rl, R2 and RV1, The negative pulse triggers the IC and the output (pin 3)....
-
Liquid crystal displays are currently available in several versions and various sizes. The wide variety of features, has resulted in there a little chaos in the provision of the pin. So that even when, after much effort, we can find a screen that fits our....
-
This circuit shows how to cascade counters and retain correct leading zero blanking. The NAND gate detects whether a digit is active since one of the two segments a or b is active on any unblanked number. The flip flop is clocked by the least significant....
-
The circuit provides a simple means of determining the succession of phases of a 3-phase 120 V source used in synchro work. Terminals A, BT and C are connected to the three terminals of the source to be checked. If the neon bulb lights, interchange any two....
-
The circuit uses a CA3130 BiMOS op amp as the sample-readout amplifier for the storage (sample-holding) capacitor Cl, and a CA3080A as the sample-control amplifier. ..
-
This circuit rapidly charges capacitor CST0 to a voltage equal to an input signal. The input signal is then electrically disconnected from the capacitor with the charge still remaining on CSTO. Since CST0 is in the negative feedback loop of the operational....
-
When switch SWl is positive, the FET is turned on, and has a resistance of about 400 ohm. The input voltage charges up the capacitor through the FET. When SWl is negative, the FET is turned off (pinched off). To get a long storage time, the op amp must have....
-
During normal' 'hold'' mode, the replicated analog voltage is buffered straight through the S/H amplifier to the output. Upon issuance of a SAMPLE signal, the S/H amplifier is placed in the hold mode, holding the voltage until the new analog voltage is....
-
Any good power transistor can be used in this circuit. The base resistor should be adjusted to obtain a pulse rate of about 50 pulses per minute. The range of values shown can go from 10 pulses to 100 pulses per minute. The single fence wire must be....
-
The output of a video amplifier is differentiated before being fed to a Schottky comparator. The propagation delay is reduced to typically 10ns. The output pulse width is set by the value of C, lOOpf giving a pulse of about 90ns duration.
..
-
A photocell circuit provides automatic threshold adjustment. Monostable action prevents undesired retriggering of the output. With only one op amp IC, the circuit offers: Automatic adjustment of its trigger level to accommodate various light sources, changes....
-
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 is a 3 stage discrete amplifier with gain control. Alternative transistors such as BC109C, BC548, BC549, BC549C may be used with little change in performance. The first stage built around Q1 operates in common base configuration. This is unusuable in....
-
Well, it's pretty much a PAiA preamp - usual input circuity followed by one half of dual op-amp rigged in fixed 20dB amplification circuity, followed by second stage which is adjustable for up to 40dB amplification, for up to 60dB total. The power supply is....
-
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....
-
Resistor R1, capacitor C1, and two converters form a square wave generator, which produces the basic tone. The generator is sui followed by an inverter which serves as both a buffer and a driver for the President. The resistor R2, which has a minimum value....
-
One small spot of rain on the sense pad of this bleeper will start this audio warning. It can also be operated by rising water. The circuit has two transistors, with feedback via capacitor Cl, but Trl cannot operate as long as the moisture sense pad is dry. ..
-
If load current requirements are relatively low (i.e. maximum forward rms current 500 mA), an ac solid state relay can be constructed quite simply by the connection of two H11C optically coupled SCRs in a back-to-back configuration as illustrated.
..
-
The control of both direction and of proportional motor speed is achieved by rotation of a single potentiometer. The motor driver is an SGS integrated circuit L293 which will drive up to 1 amp in either direction, depending on the logic state of input 1 and....
-
Speed control is accomplished by pulse width modulating the gates of two MGP20N45 TMOS devices. Therefore, motor speed is proportional to the pulse width of the incoming digital signal, which can be generated by a microprocessor or digital logic. The....
-
Stepping motors find wide use in disk drives and machine control. MOSPOWER transistors are ideal motor drivers because of their freedom from second breakdown. Note that snubbing networks are not used because load line shaping is not necessary with MOSPOWER....
-
A shortcoming of the above bi-directional proportional motor control circuit is that with the potentiometer in its center position the motor does not stop, but creeps due to the difficulty in setting the potentiometer for an exact 1:1 mark-space ratio from....
-
The use of power MOSFETs allows a direct interface between logic and motor power, which permits circuit simplicity as well as high efficiency. This speed control circuit can be packaged on a 22-pin, double-sided, 3.5 4-in. pc board. A 12 V control supply....
-
Power op amps provide accurate speed control for dc motors. The circuit provides bidirectional speed control. The amplifiers' push-pull configuration ensures a full rail-to-rail voltage swing (minus the output stages' saturation drops) across the motor in....
-
Because of its high amplification factor and built-in power-output stage, an integrated power operational amplifier makes a convenient driver for ac motors. One op amp can be configured as an oscillator to generate the required ac signal. The power-output....
-
The modified power-factor controller, developed at the Marshall Space Flight Center, employs a phase detector for each of the three phase windings of a delta-connected induction motor. The phase-difference sum is the basis for control.
..
The purpose of the circuit is to hold the peak of the input voltage on capacitor Cl, and read the value, V0, at the output of U2. Op amps Ul and U2 are connected as voltage followers. When a signal is applied to Vj, Cl will charge to this same voltage....
The SN75604, with input control logic but requiring only one supply rail, can be used in the "lights on" sensor and alarm driver. The device Vqq and enable inputs are connected to a voltage lead from the light switch. The direction control input is connected....
The circuit is used to indicate two different water temperature trip points by turning on LEDs when the temperatures are reached. The circuit is constructed around the LM2904 dual operational amplifier powered from the 12 V auto system. The thermistor is in....
The circuit warns car drivers when the air temperature close to the ground approaches 0°C, thereby indicating possible formation of ice on the road surface. Op amp A1 is wired as a voltage level sensor. Op amp A2 is wired as an astable multivibrator which,....
The Digi-Tach contains a master-clock circuits (U6)v latch and reset pulse generators (U2-b-U2-d), input signal bonditioner (Ul, U2-a), pulse counter (U3), display and display drivers (DIS1, DIS2, U4, and U5), and a voltage regulator (U7)...
A PC usually requires a plug-in ADC card to process analog signals. However, with the circuitry in Figure 1, a PC can communicate with an 18-bit ADC through its serial port. The port provides both positive and negative power supplies as well as control....
Here is a circuit for using the printer port of a PC, for control application using software and some interface hardware. The interface circuit along with the given software can be used with the printer port of any PC for controlling up to eight equipment .....
The circuit can be easily built to a small plastic box with telephone connectors in both ends. The circuit takes about 10-20 mA current, so if the circuit is not in use all the time it is best to use batteries. You can also use small wall transformer to....
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....
This article describes an I-V curve tracer circuit that uses a computer for display and control. The circuit is controlled via the PC parallel port. Software is provided, written in BASIC, to control the measurement and display the results on the monitor.....
PC parallel port can be very useful I/O channel for connecting your own circuits to PC. The PC`s parallel port can be used to perform some very amusing hardware interfacing experiments. The port is very easy to use when you first understand some basic....
Using the simple circuit in Figure 1, you can control the light intensity in your room or work area from your PC. The heart of the circuit is a low-power D/A converter that converts digital words from a computer's parallel port to analog-voltage signals. To....
This project was begun as a means to charge and cycle NiCad batteries but has become a versatile tool for experiments requiring either a controlled voltage up to +30V and/or a current of +/- 2.5 Amps. If all you want to do is charge and recycle NiCad....
The circuit in Figure 1 controls 32 voltage-output channels from the parallel port of a PC. The circuit comprises eight DAC7615 quad voltage-output, serial-data programmable, 12-bit DACs. The controlling PC individually programs each of the 32 DAC channels,....
The Dallas Semiconductor (www.dalsemi.com) DS1722 digital thermometer allows measurement resolution as fine as 0.0625°C in digital form and with linear response. The accuracy specification is only 2°C, but you can improve this figure by careful calibration.....
You can use the parallel port of your PC and a few additional components to generate a powerful, easy-to-use arbitrary-waveform generator. By using a Visual Basic program with the circuit in Figure 1, you can generate any waveform (for example, sinusoid,....
This is a very easy and fun to build project that will allow you to control up to eight external devices through your computer`s parallel port. You may for instance control different appliances such as lamps, computers, printers, tv sets, radios, music....
Differential multiplexers are generally used in process control applications to eliminate errors due to common mode signals. In this circuit however, advantage is taken of the dual multiplexing capability of the switch. This is achieved by using the....
a low cost, high-speed monolithic analog multiplexer. The system works as follows: Selects a channel and initiates a conversion at G = 1 and then looks at the MSB of the conversion result. If the MSB = 1, the ?? will store the value. If the MSB = 0, the ??....
When computer peripheral equipment is interfaced, it is convenient to work with logic signal levels. With a nominal 4 V at the output dropping to - 0.6 V on illumination, this circuit reflects the requirements of a high-speed, paper tape optical reader....
Anyway, Fluffy is a SX programmer for people who have already experimented with PIC chips, and want to try out the Scenix SX family. I built Fluffy because I wanted to experiment with the SX's, but didn't want to spend $300 or so bucks on the official....
The preamplifier is protected from excessive input signals of either polarity by the 2N5909 junction field-effect transistor. A nulling circuit makes it possible to set the preamplifier output voltage to zero at a fixed low level (up to + 10~8A) of the input....
The circuit utilizes CA3160 and CA3140 BiMOS op amps to provide a full-scale meter deflection of ± 3 pA. The CA3140 serves as an 1T0 gain stage to provide the required plus and minus output swing for the meter and feedback network. ..
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. ..
The circuit consists of two basic circuits, the oscillator and the detector. The oscillator uses an FET in a Colpitts configuration. The energy circulating in the oscillator tank is coupled through C4 to the detector circuit, where a small diode (D2)....
The circuit uses two general-purpose npn transistors, Ql and Q2, and a special hand-wound, dual-coil probe ferrets out the magnetism. Ql and its associated components form a simple VLF oscillator circuit, with LI, C2, and C3 setting the frequency. The VLF....
A simple tester can be used for routine checks for resistance on production lines of relays, coils, or similar components where frequent changes in resistance to be tested are not required. The tester is built around a single quad op amp chip, the LM324. R,....
The pitch of the tone is dependent upon the resistance under test. The tester will respond to resistance of hundreds of kilohms, yet it is possible to distinguish differences of just a few tens of ohms in low-resistance circuits. Ql and Q2 form a....
A bubble vial with external aluminum-foil electrodes is the sensing element for a simple indicating tiltmeter. To measure bubble displacement, a bridge circuit detects the difference in capacitance between the two sensing electrodes and the reference....
The device is a dc switch that is normally on via the forward biasing of Ql via R3. Ql now clamps Q2 into a forward state by biasing its complement well into a saturated state via R4. The dc switch is turned off via a negative voltage above that of the zener....
A small neon lamp is triggered into conduction by the telephone's ringing voltage, passes just enough current to activate the LED in optocoupler Ul, which in turn triggers the 6-A Triac that controls 12—a 117-Vac lamp or bell. (Capacitor Cl is necessary....
The heart of the circuit is IC1, General Instrument's AY-3-1350 melody-synthesizer IC. IC2 is a TCM1512 telephone ring detector IC that is powered by the telephone line. The circuit's operation begins when IC2 senses a ring pulse on the telephone line. The....
A 2N5777 photo-Darlington cell picks up blinking light from the transparent plastic buttons. The power is switched ON and OFF by a hi-beta 2N3904 transistor. The circuit's 9 V battery can be left continuously connected. Less than a micro-ampere is drawn-even....
This circuit functions as a line-current sensor and can be connected in series with either of the phone lines. For the circuit to indicate an "in use" status for all phones on a single line, it must be connected in series with the phone line before, or ahead....
As you can see, there is only one regulated 12 volt supply operating the entire circuit. I was able to do this simply by AC coupling the received signal to U3 via C10. This allowed me to adjust the offset within an operating window. By using a tantalum....
Locator uses a transistor radio as the de-tector. With the radio tuned to a weak station, adjust Cl so the locator oscillator beats against the received signal. When the search head pas¬ses over metal, the inductance of LI changes thereby changing the....
When the soil is moist, the LED glows. If the moisture falls below a certain predetermined level, the LED begins to flash. If there is still less moisture, the LED turns off. To calibrate, connect the battery and insert the probe into a container of dry....
When the 14B-12B pair opens, 12B is connected to Al's summing point via 13B. The sensor now discharges into the summing point through the 1 µ capacitor. Since the charge voltage is fixed, the average current into the summing point is determined by the....
The laser light detector utilizes a sensitive photo transistor (Q5) placed at the focal point of a lens (LE2). The output of Q5 is fed to a sensitive amplifier consisting of array (Al) and is biased via the voltage divider consisting of R14 and Rl. The base....
A cadmium sulfide photocell (LDR1, which is a light-dependent resistor) is connected to the base and collector of an npn transistor, Ql. When light hits LDR1, the internal resistance goes from a very high (dark) value to a low (light) value, supplying base....
The circuit is light seeking; it will follow a flashlight around a darkened room. A pair of photocells determine the direction in which the robot will move. Each photocell is connected to an op amp configured as a comparator. When sufficient light falls on....
M1 is a stepper taken from an old disk drive. There are five pins, i.e., common, coil 1, 2, 3 and 4. Resistance measured between common pin and each coil is about 75 Ohms. Driving current for each coil is then needed about 60mA at +5V supply. A darlington....
Some applications may not need user display and key interface, dump terminal is an alternative way for program setting, displaying user interfacing command.Debugging, dump terminal connects with serial port, use only 2-i/o pin, P3.0 for Rxd and P3.1 for Txd.....
This circuit was designed to control a 32 channel Christmas light show from the PC serial port. Originally designed with TTL logic, it has been simplified using CMOS circuits to reduce component count. It is a fairly simple, reliable circuit that requires....
If you are looking at this page, you probably feel like I did when I tried to run a self-powered PIC programmer with my notebook computer. Yes, the serial port was the ultra-low-power type and wouldn`t provide enough current to power the programmer. The....
This is a page of analogue interfaces for joysticks. Although these interfaces have been developed for use with 4QD`s controllers they will have plenty of other uses. Also because of the development history, we have printed circuit boards available (either....
If you have access to a Lowe HF-225 shortwave receiver, then you might be interested in this page. If you don`t, then you`d probably be better off leaving now. What follows is a project I completed some time ago, which allows the Lowe HF-225 to be controlled....
The circuit in Figure 1 is an RS-232/485 converter that uses the transmitted signal itself to control the flow. The circuit uses MAX232 and MAX483 interface circuits, IC1 and IC2 from Maxim Integrated Products (http://www.maxim-ic.com) to convert between the....
I got a problem with my notebook, because it has only COM1. My programmer board, Easy-Downloader must use serial port and the application board also needs to communicate via the same serial port. I do remembered I have to swap DB9 connector of both devices....
The circuit will operate reliably from below 1 MHz to above 400 MHz. With Vcc = 5 V the output of the second inverter essentially attains a full swing from 0 V to 5 V. Such large logic output levels and broad frequency range capabilities make this oscillator....
This circuit has been designed to provide a clearly visible light, formed by 13 high efficiency flashing LEDs arranged in a pseudo-rotating order. Due to low voltage, low drain battery operation and small size, the device is suitable for mounting on bicycles....
The first circuit energizes the relay when the light rises above the preset level. The second circuit energizes the relay when the light falls below the preset level. The two circuits are practically identical. The only difference between them is the....
The circuit uses a free-running push-pull dc to dc high voltage converter to get the necessary voltage for the laser plasma tube supply. The supply voltage Vc of this converter, is adjusted by a switch-mode power supply in order to keep the load current....
This project flashes eight LEDs in an apparently random manner. It uses a 4060 combined counter and display driver IC which is designed for driving 7-segment LED displays. The sequence is not really random because seven of the LEDs would normally be the....
A very simple LED flasher circuit. With HT-2014L the circuit produces 1 flash per second and the HT-2014M produces 2 flashes per second...
A relaxation oscillator is used to flash an LED in the base circuit. Cl is charged slowly through R1 by the power source, then discharged periodically through R3 and the LED by the UJT. ..
The LED is the CSL310L which contains a red LED and a green LED connected back to back and mounted close together in a single moulding. The LED can emit red or^green light by controlling the polarity of the applied voltage and if the polarity is switched at....
A simple and effective receiver for actuating garage doors, alarms, warning systems, etc. The SCR, which has a very low trigger current 30 µ is typical—it requires an input power of only 30 juW to activate the relay. A high Q tuned antenna circuit assures....
This general purpose signal source serves very well in signal-tracing applications. The output level is variable to more than 1 Vrms into a 50 O load. Almost any crystal in the 1 to 15 MHz range can be used. Ql forms a Colpitis oscillator with the output....
A high speed oscillator is possible by combining an MECL 10 crystal oscillator with an MECL III frequency doubler as shown. One section of the MC10101 is connected as a 100 MHz crystal oscillator with the crystal in series with the feedback loop. The LC....
The FET input amplifier has fixed bias with source feedback. This provides a very high input impedance with very low capacitance. The FET amplifier drives an emitter follower which, in spite of the fact that it has a low output impedance, feeds a transformer....
Digital ICs and opto-isolators provide the drive for this TMOS servo amplifier, resulting in fewer analog circuits and less drift. Fast and consistent turn-on and turn-off characteristics also enable accurate analog output results directly from the digital....
The signal from a synchro receiver or a variable resistive cam follower (potentiometer) is boosted by operational amplifier Ul, whose output swing is limited by back-to-back zeners D3 and D4. The signal is then applied to operational amplifiers U2 and U3,....
U1A, an op amp, oscillates at the frequency at which the phase shift in the Wien bridge network is exactly zero degrees. Changing bridge component values changes the oscillator frequency. In this circuit, we need change only the two resistors to do this. S1A....
L1 is a loop of 10 to 20 turns of insulated wire with a diameter anywhere between 4" to 4'. Oscillator frequency (7 to 30 MHz) shifts substantially when a person comes near or into the loop. This oscillator together with a resonant detector might make a very....
This circuit generates simultaneously, a triangle and a square waveform. It is self starting and has no latch up problems. IC1 is an integrator with a slew rate determined by CT and RT and IC2 is a Schmitt trigger. The output of IC1 ramps up and down between....
With only three components and a buffer, a line frequency square wave having a 1:1 duty cycle may be derived from the power supply. During the alternate half-cycle, however, A is effectively clamped to - 0.7 V by Dl in the bridge which offsets the forward....
This circuit gives a 3 phase square-wave output for a variable speed motor drive. Operation is straightforward, the 4017 counter is synchronously reset after six clock inputs. The she outputs are combined to give the required waveforms. It is interesting to....
The current source formed by Ql in conjunction with capacitor Cl set the duration time of the ramp. As the positive dc voltage at the gate is changed, the peak point firing voltage of the PUT is changed, which changes the duration time...
A1 and its associated components furnish an amplitude stable sine wave source. All positive feedback path is a Wein bridge, tuned for 1.5 kHz, Ql, the LT1004 reference, and additional components in Al's negative loop unity-gain stabilize the amplifier. Al's....
This is the timekeeping test circuit. It includes a one-transistor circuit to switch in the 5V power supply when present and drop back to the 3v battery the rest of the time. That loop of blue wire-wrapping wire is a lariat used to quickly and easily pull....
Nowadays the batteries are gaining more and more power, being the only components that fail to provide energy for portable electronic devices. The evolution is rapid, leading manufacturers electronic equipment to attempt to minimize the consumption of their....
The governor following is intended to regulate the light intensity incandescent 220 V. The components in a relatively few, which means it can easily be mounted onto a small plate. After the build, we recommend you place it inside the box which is flush....
Door open alarms are used chiefly in automotive, industrial, and appliance applications. This type of circuit can sense the opening of a refrigerator door. When the door opens, a triac could be activated to control the inside light. The figure shows a door....
A negative pulse at the input is fed via capacitor Cl to the input pin (2) of the IC, Pin 2 is held slightly above its triggering voltage of 1/3 Vcc by the voltage divider comprising Rl, R2 and RV1, The negative pulse triggers the IC and the output (pin 3)....
Liquid crystal displays are currently available in several versions and various sizes. The wide variety of features, has resulted in there a little chaos in the provision of the pin. So that even when, after much effort, we can find a screen that fits our....
This circuit shows how to cascade counters and retain correct leading zero blanking. The NAND gate detects whether a digit is active since one of the two segments a or b is active on any unblanked number. The flip flop is clocked by the least significant....
The circuit provides a simple means of determining the succession of phases of a 3-phase 120 V source used in synchro work. Terminals A, BT and C are connected to the three terminals of the source to be checked. If the neon bulb lights, interchange any two....
The circuit uses a CA3130 BiMOS op amp as the sample-readout amplifier for the storage (sample-holding) capacitor Cl, and a CA3080A as the sample-control amplifier. ..
This circuit rapidly charges capacitor CST0 to a voltage equal to an input signal. The input signal is then electrically disconnected from the capacitor with the charge still remaining on CSTO. Since CST0 is in the negative feedback loop of the operational....
When switch SWl is positive, the FET is turned on, and has a resistance of about 400 ohm. The input voltage charges up the capacitor through the FET. When SWl is negative, the FET is turned off (pinched off). To get a long storage time, the op amp must have....
During normal' 'hold'' mode, the replicated analog voltage is buffered straight through the S/H amplifier to the output. Upon issuance of a SAMPLE signal, the S/H amplifier is placed in the hold mode, holding the voltage until the new analog voltage is....
Any good power transistor can be used in this circuit. The base resistor should be adjusted to obtain a pulse rate of about 50 pulses per minute. The range of values shown can go from 10 pulses to 100 pulses per minute. The single fence wire must be....
The output of a video amplifier is differentiated before being fed to a Schottky comparator. The propagation delay is reduced to typically 10ns. The output pulse width is set by the value of C, lOOpf giving a pulse of about 90ns duration. ..
A photocell circuit provides automatic threshold adjustment. Monostable action prevents undesired retriggering of the output. With only one op amp IC, the circuit offers: Automatic adjustment of its trigger level to accommodate various light sources, changes....
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 is a 3 stage discrete amplifier with gain control. Alternative transistors such as BC109C, BC548, BC549, BC549C may be used with little change in performance. The first stage built around Q1 operates in common base configuration. This is unusuable in....
Well, it's pretty much a PAiA preamp - usual input circuity followed by one half of dual op-amp rigged in fixed 20dB amplification circuity, followed by second stage which is adjustable for up to 40dB amplification, for up to 60dB total. The power supply is....
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....
Resistor R1, capacitor C1, and two converters form a square wave generator, which produces the basic tone. The generator is sui followed by an inverter which serves as both a buffer and a driver for the President. The resistor R2, which has a minimum value....
One small spot of rain on the sense pad of this bleeper will start this audio warning. It can also be operated by rising water. The circuit has two transistors, with feedback via capacitor Cl, but Trl cannot operate as long as the moisture sense pad is dry. ..
If load current requirements are relatively low (i.e. maximum forward rms current 500 mA), an ac solid state relay can be constructed quite simply by the connection of two H11C optically coupled SCRs in a back-to-back configuration as illustrated. ..
The control of both direction and of proportional motor speed is achieved by rotation of a single potentiometer. The motor driver is an SGS integrated circuit L293 which will drive up to 1 amp in either direction, depending on the logic state of input 1 and....
Speed control is accomplished by pulse width modulating the gates of two MGP20N45 TMOS devices. Therefore, motor speed is proportional to the pulse width of the incoming digital signal, which can be generated by a microprocessor or digital logic. The....
Stepping motors find wide use in disk drives and machine control. MOSPOWER transistors are ideal motor drivers because of their freedom from second breakdown. Note that snubbing networks are not used because load line shaping is not necessary with MOSPOWER....
A shortcoming of the above bi-directional proportional motor control circuit is that with the potentiometer in its center position the motor does not stop, but creeps due to the difficulty in setting the potentiometer for an exact 1:1 mark-space ratio from....
The use of power MOSFETs allows a direct interface between logic and motor power, which permits circuit simplicity as well as high efficiency. This speed control circuit can be packaged on a 22-pin, double-sided, 3.5 4-in. pc board. A 12 V control supply....
Power op amps provide accurate speed control for dc motors. The circuit provides bidirectional speed control. The amplifiers' push-pull configuration ensures a full rail-to-rail voltage swing (minus the output stages' saturation drops) across the motor in....
Because of its high amplification factor and built-in power-output stage, an integrated power operational amplifier makes a convenient driver for ac motors. One op amp can be configured as an oscillator to generate the required ac signal. The power-output....
The modified power-factor controller, developed at the Marshall Space Flight Center, employs a phase detector for each of the three phase windings of a delta-connected induction motor. The phase-difference sum is the basis for control. ..