The first amplifier circuit is a bird phone. In this circuit, the electret mike (MIC1) is mounted in the neck of a large plastic funnel. The amplifier, built around an MC34119 (which is available from D.C. Electronics, P.O. Box 3203, Scottsdale, AZ 85271-3203; Tel. 800-467-7736, and elsewhere), is then placed outside of the funnel with the pickup facing a nearby bird feeder. The output of the amplifier is then connected to a 16- speaker. The amplifier`s voltage gain is.....
This ultra wide range timer uses a 555 timer base, two 4017Bs and a 4020B that act as frequency dividers that can be switched in and out...
This simple circuit consists of only two timing components Rr and Cr, the NE555, and bypass capacitor C2. While not essentiaHor operation, C2 is recommended for noise immunity. During standby, the trigger input terminal is held higher than 1/3 Vee and the output is low. When a trigger pulse appears with a level less than 1/3 Vce, the timer is triggered and the timing cycle starts. The output rises to a high level near Vcc. and at the same time, Crbegins to charge.....
This circuit prevents making transmissions that are too long, which "time out" repeaters and/or tie up a communicatio..
The timer circuit shown gives independent control of the output"s on and off intervals, which can range from 0.055 seconds to 30 minutes, relatively unaffected by power-line transients. IC1 is a CMOS programmable-timer chip that includes 24 ripple-binary counter stages; the first eight are bypassed when logic 1 is applied to pin 6. Then, a 4-bit input code at pins A, B, C, and D connects one ofthe 16 remaining stages to the output at pin 13. ..
By utilizing both halves of the dual timer it is possible to obtain sequential timing. By connecting the output of the first half to the input of the second half via a 01 Âµ-F coupling capacitor, sequential timing may be obtained. Delay ti is determined by the first half and h by the second half delay. The first half of the timer is started by momentarily connecting pin 6 to ground..
The watchdog timer contains a counter, IC3, in addition to the usual retriggerable 555 timer, ICl. The counter will so..
Using an RC oscillator, an up to 24-stage ripple counter O) 16777216 or 2U, and a 0.1-Hz count-rate with #..
By using three 555 ICs, three sequential pulses can be generated...
After one cycle of operation, SCR 1 will be on, and a low value of voltage is applied to the UJT emitter circuit, interrupting the tuning function. When pushbutton SI is pushed, or a positive going pulse is applied at point A, SCR 2 will turn on, and SCR 1 will be turned off by commutating capacitor CC. With SCR 1 off, the supply voltage will be applied to RE and the circuit will begin timing again...
Many applications, such as computers, require signals for initializing conditions during start-up. Other applications such as test equipment require activation of test signals in sequence. SE555/NE555 circuits may be connected to provide such sequential control..
This timer is ideal for small aplications. Due to its simple structure, its usage and nevertheless its universal character, this mini timer is usable in the most current applications needing time intervals, from some seconds through approximately 60 minutes. By simple modifications it is possible to adjust the maximum time and the timing scale, as necessary. A strong output, made by a relay, permits to adapt, on the input and the output, whatever apparatus...
Using one current source for tbe charge and discharge path in this circuit ensures identical rise and fall times at the capacitor terminal. A Darlington pair ensures identical biasing of the IC during the charge and discharge cycles. The period of the triangle wave is: T=0.46VC1/R2. ..
Load current starts approximately 0 RC..
The circuit is built around a 555 oscillator/ timer. The circuit provides two time periods. The long-running time period is adjustable from about 1 to 10 minutes, and the short time period is preset to about three seconds. Here`s how the dual timer operates. When the power is switched on, G2 begins to charge through R3, Rl, Dl, and R4 to start the long-term timer period. When the voltage across C2 reaches the 555`s internal switching point, the long-term timer times out,.....
Rl and R2 hold the inverting input at half supply voltage. R4 applies feedback to increase the input impedance at pin 3. Pin 3, the nonin-verting input, is connected to the junction of R3 and C. After the switch is opened, C charges via R3. When the capacitor has charged sufficiently for the potential at pin 3 to exceed that at pin 2 the output abruptly changes from 0 V to positive line potential. If reverse polarity operation is required, simply transpose R3 and C..
The time base is first selected with Sl set for seconds or minutes, then units 0-99 are selected on the two thumbwheel switches S4 and S5. Finally, switch S2 is depressed to start the timer. Simultaneously, the quartz crystal-controlled divider circuits are reset, the ICM7250 is triggered and counting begins. ..
When Sl is off, Cl charges to within 0.5 V of the battery voltage through diode Dl and resistor R4. When Sl is closed, tbe anode of tbe PUT rises to the positive supply voltage. The PUT does not conduct, because battery voltage appears in series with tbe charge stored on Cl, which raises the gate of the PUT to a level positive with respect to the anode. ..
This circuit adapts a frequency counter to measure intervals. It was originally used as a shutter speed checker for a photo application. The watch ticks are clipped and shaped and formed into a square wave. This square wave is used to gate an accurately known clock (1-MHz TTL XTAL OSC) and an external counter is used to directly count the clock pulses during the interval to be measured...
Transistor Ql and resistors Rl, R2, and R3 form a constant current source and the charge current might be adjusted..
Transmitters & Receivers
Sensors & Detectors
Low Frequency Amplifiers
Regulated Power Supplies