Various Circuits

The circuit in Figure 1 tests these characteristics. It charges the capacitor under test through 100 kΩ for approximately 1 msec and then discharges it through 10Ω for approximately 40 nsec. The cycle then repeats. The circuit uses a double-sided copper-clad pc board. All the components except the 10Ω resistor connect to one side of the board, so they can benefit from shielding by the cast-aluminum enclosure (Figure 2).

This application note implements a 24-hour digital clock, alarm and 99 minute 59 second count down timer, yet operates on two ?AA? batteries. The PIC16C54A is perfect for this application, due to it?s small size, high current I/Os with direct LED drive, low cost, fast instruction throughput and low frequency/current operation.

The 2x trigger is a little involved, but here is a circuit that will do divide by two preserving pulse width. You can use a 74LS00 for the NAND gates and a 74LS74 for the flip-flop. I think both are available at Radio Shack. Enjoy!

The circuit accepts an input clock of any duty cycle and generates any desired duty cycle at the output. You need to add only one flip-flop to the earlier design to generate an arbitrary-duty-cycle output. You can use the circuit to correct a non-50% input to a 50% output or to create a non-50% output from any arbitrary input duty cycle.

Excellent clock generator to drive 4017 type cmos circuits.

Using a standard PLL circuit, such as the CMOS 4046B with some passive components, is a well-known way to design a clock multiplier. Unfortunately, using a PLL in a digital circuit has two disadvantages: It takes a long time for the circuit to reach a stable output frequency, and the frequency-drift compensation has a complex design.

The full-scale deflection of the universal high-input-resistance voltmeter circuit shown in the figure depends on the function switch position as follows: (a) 5V dc on position 1 (b) 5V ac rms in position 2 (c) 5V peak ac in position 3 (d) 5V ac peak-to-peak in position 4 The circuit is basically a voltage-to-current converter. The design procedure is as follows: Calculate RI according to the application from one of the following equations: (a) dc voltmeter: RIA = full-scale EDC/IFS (b) rms ac voltmeter (sine wave only): RIB = 0.9 full-scale ERMS/ IFS (c) Peak reading voltmeter (sine wave only): RIC = 0.636 full-scale EPK/IFS (d) Peak-to-peak ac voltmeter (sine wave only): RID = 0.318 full-scale EPK-TO-PK / IFS

A differential amp used by the SIM, and it is a completely conventional circuit. This is adjustable by using VR1 to null out any normal variations that the amp might show when there is no distortion or other nastiness in evidence. The second stage is a high gain amplifier, and will amplify the residual signal to a level suitable for the rectifier and indicator circuits.

This station is supplied with a ST3 1/8" screwdriver tip. Seems to be suitable for almost all jobs, minus some fine-soldering jobs on surface mount boards. I was unable to order replacement parts (heater) for my older model I was forced to purchase a new station, not really expensive though, they are around $55.00 Canadian in my area so a good buy.

This circuit uses a 74HCT74, 74HCT00, and a LM311 to form a frequency comparator. The two pulse trains are fed to two D-type flip-flops (triggered by the leading edges). The flip-flops' outputs are compared in a NAND gate. If the output of the NAND gate becomes "0", the flip-flops are reset. If the frequency of F1 is higher than the frequency of F2, the signal "Q2" consists of needles and "Q1" is a pulse train.