Analog Dial AVO Amps-Volts-Ohms meter

Many times we cannot carry big or expensive test instruments to the field, so we have to have a troubleshooting tool kit. Continuity testers, Logic Probes, DMM, Clamp Meters etc.. You can troubleshoot and repair Electronic Equipment easily with Meters and Continuity Tester

It also is sometimes required to build a quick jig or fixture with electronics to troubleshoot, simulate a problem or to test the reliability or aging of components and systems. Here you need to be cost effective, fast and innovative; and build a simple system with available, affordable or procurable resources. Hence a bit of circuit design, firmware and software are essential skills for production engineering.

This was designed, keeping in mind, that sometimes we have few components available and we could be flat broke. Even that you could not carry your DMM somewhere, but you have to make some instrument for a quick need with what is available. If you are out of cash or feel like Robinson Crusoe, then this is a low cost measurement system. I designed it to practice on eagle, i am not sure how this circuit may work, it is not tested . But i have built, repaired and designed many DMMs. So there is a fair chance, parts of it may work :~)

IC3 LM555 is to generate -5V from 9V. That reminds me of a story, In 1986 while i was studying BE electronics i got a chance to work part-time in a company that sold-serviced imported instruments, it was called trans-marketing. They were the agents for Racal-Dana, Genrad, Data I/O and so many more. Here i came across a Book called CMOS Hot Ideas of Intersil. I had a chance to observe, build and learn some things here. The ICL7107 circuit was the most fascinating, I also read the books of National Semiconductor here.

Analog Dial AVO Amps-Volts-Ohms meter

In those days small firms used to make DPM's digital panel meters with 7107. In 1987 when i got a oppurtunity to design a DPM for a firm, I put the 555 clock in place CD4009 clock shown in intersil, to derive the -5.

Potentiometer Dial GIF for above circuit to be used to make a hand-held avo-meter is here.

Small Electronic Testing Tools - Analog Dial AVO Amps-Volts-Ohms meter

Preset Digital BCD Counter

See a Tutor Digital up down BCD counter that will help you take the first step in digital electronics.

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Counter Lab - The Counter can be tested by clicking the buttons given below, Watch the LEDs and seven segment display. Inc, Dec, and Set buttons are momentary acting and Clk Button is latching type. The Dip Switch in the Left also can be set by clicking on each of them, watch the switch and LEDs after a click.

a. Set the DIP Switch as you like and then Press the Set button. Now you will see the BCD value in the yellow LEDs named 4029 output. The Decimal value will be seen in the seven segment Display. Now try for different dip switch settings and see the BCD LEDs and Decimal output.

b. Now Press The Inc and Dec pushbuttons and See the corresponding green LEDs which indicate the state of the Nand gate 4093 Flip Flop. Set it to Increment up-count or Decrement which is down-count.

c. Now Click the Clk - clock or count button, the switch will latch, press it again to release. If you toggle it once the counter will get a single pulse and it will count it, see the BCD and decimal displays. Now you turn it on and leave it, the counter will keep counting one per second till you turn it off, the clock nand gate is wired to be an oscillator.