Transistor Ql and resistors Rl, R2, and R3 form a constant current source and the charge current might be adjusted..

This circuit uses a 555 timer in the bistable mode. Touching T2 causes the output to go high; D2 conducts and D1 extinguishes. Touching T1 causes the output to go low; D1 conducts and D2 is cut off. The output from pin 3 can also be used to operate other....

Using a 4060 CMOS binary divider and built-in clock oscillator, a long-duration timer can be made veiy simply. The solid-state relay can be sized for your application, and can be replaced with a mechanical relay if a suitable power supply is available. With....

See (a) for the timing information for the alarm circuit in (b). When leaving your vehicle, flip the arming switch and close the door to arm the device. Subsequent opening of an entrance triggers both timers. After the expiration of the entry delay timer,....

The baby-alert transmitter is built around an LM324 quad op amp (Ul), two LMC555CM CMOS oscillator/timers (U2 and U3), and a few support components. The transmitter sends a signal on receipt of a sound at MIC1...

Press SI. The 100 µF electrolytic capacitor rapidly charges up at about 0 V. The transistor will be forward biased, and collector current will flow operating the relay. Release SI. The capacitor will begin to discharge via the 33 K resistor at the base of....

This circuit"s frequency of oscillation increases directly with light intensity. The greater the light intensity, the higher the frequency of the oscillator. The 555 timer operates in the astable oscillator mode where frequency and duty cycle are....

The circuit"s input op amp triggers the timer, sets its flip-flop and cuts off its discharge transistor so that capacitor C can charge. When capacitor voltage reaches the timer"s control voltage of 0.33 Vee. the flip-flop resets and the transistor....

The HA7210 oscillator 10 combines with an IOL7642 quad CMOS op amp to produce a sleep-mode control circuit. The circuit is put into the sleep mode with a logic high applied to the Reset input or with an RC timer for automatic reset...

The timing components are Rl, R2, and C,. Cl is a bypass capacitor used to reduce the effects of noise. At start-up, the voltage across C, is less than the trigger level voltage (1/3 Vnn). causing the timer to be triggered via pin 2. The output of the....

This straightforward circuit uses an NE555 timer as an oscillator, a 7493 counter chain and a DAC0806 D/A conver..

Two 555s and a quad NAND-gate IC can simulate an electrocardiograph signal and a -y-wave radioisotope signal for applications in nuclear medicine. This circuit synchronizes the radioisotope signal to the EKG signal. You can use the circuit"s outputs to....

A three-way switch to control a lamp (off-dim-bright, etc.) uses an NE555 timer to generate a one-second pulse, trigge..

To safeguard portable, emergency power repeaters from reverse or excessive voltage, Dl prevents incorrect polarity damage, and zener voltage determines the maximum voltage that will reach the rest of the circuitry..

This circuit combines a 555 timer with a 2N2222 transistor and an external potentiometer. The pot adjusts the output voltage to the desired value. To regulate the output voltage, the 2N2222 varies the control voltage of the 555 IC, increasing or decreasing....

Timer Ul operates as a free-running oscillator at 60 Hz, providing trigger pulses to timer U2 which operates in the monostable mode. Resistor Rl is fixed and capacitor Cx is the capacitor being measured. While the output of U2 is 60 Hz, the duty cycle....

The alarm circuit has a single 555 oscillator/timer (Ul) performing double duty; serving both in the alarm-trigger circuit arid the entry- delay circuit. In this application, the trigger input of IJ1 at pin 2 is held high via Rl. A normally-closed sensor....

This battery saver circuit can automatically turn off a small piece of test equipment after a desired period of time, allowing you to leave your shop worry free.This circuit uses a CD4011IC to act as a simple timer. One section acts as an RC discharge timer....

Capacitor C 1 charges through resistor Rl, and when the gate level established by potentiometer R2 is high enough, the SCR is triggered. Current flows through the SCR and earphones, discharging Cl. The anode voltage and current drop to a low level, so....

This circuit uses the low power ICM7555 (CMOS 555) to generate the gating, STORE and RESET signals. To provide the gating signal, the timer is configured as an astable multivibrator. The system is calibrated by using a 5 M potentiometer for Ra as a coarse....

This low-power inverter uses only 9 parts and turns 10 to 16 Vdc into 60-Hz, 115-V square-wave power to operate ac equipment up to 25 W. The first section of the 556 timer chip is wired as an astable oscillator with R2 and C1 setting the frequency. The....

In the 556 timer, the timing is a function of the charging rate of the external capacitor. For long time delays, expensive capacitors with extremely low leakage are required. The practicality of the components involved limits the time between pulses to....

This source is selected by pressing momentary-contact pushbutton switch SI. Switch SI is connected to the trigger of a 555 oscillator/timer (Ul) configured as a monostable multivibrator, wliich generates one short output pulse for each press of SI. That....

If the input frequency is known, the timer can easily be used as a frequency divider by adjusting the length of the timeing cycle. Figure shows the waveforms of the timer when used as a divide-by-three circuit...

A 555 and a dual 556 timer generate a rudimentary video signal, as shown in the schematic. The first timer generates 4.7-8 synch pulses operating in the astable mode with a 64-8 period. The second timer generates a delay pulse, which triggers the third....

This timer circuit uses a 555 IC timer and three 74LS193 counters to drive an LED display. SI is activated by one person, who turns on piezo buzzer BZ1 via Ql and also starts the clock; SI is activated by the other person being timed. ..

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....

With switch SI in the off position, as shown, battery voltage is applied across timing-capacitor CI, which stays charged while the rest of the circuitry has no power supplied to it. ..

The timer can be used wherever time periods of up to seven minutes duration are needed. To turn on just touch the turn-on plate, and after the selected time has elapsed, an alarm will sound for a short period, then automatically turn off. The turn-on touch....

A 555 timer operating in the astable mode generates the driving pulses and two 4518 dual BCD (binary coded decimal) counters provide the square waves. A TL081 op amp serves as an output buffer-amplifier, and potentiometers Rl and R2 are used in order to....

In a basic astable timer, configuration timing periods 11 and 12 are not controlled independently. The lack of control makes it difficult to maintain a constant period, T, if either 11 or 12 is varied. In this circuit, charge RAB and discharge R8 c....

When power is first turned on, two of the LEDs are on and the other two remain off until the timing cycle reverses. The LEDs flash in pairs, but by pressing and holding Sl closed until only one of the LEDs is on, and then releasing it, the four LEDs can be....