$1 DVM as Digital Input Display


Senior Member
From the cheap & easy department: I used a $1 DVM as a user input display to precisely adjust a time delay ranging from 0-5 seconds, which worked perfectly with my 5V-powered 08M2 circuit. A potentiometer voltage divider across the 5V supply easily displays on a 3-wire DVM (2-wire DVMs won't work below ~2.5 V). In my program, the Picaxe loops, continuously reads the ADC and exits when button is pressed. The ADC value times 20 gives the PAUSE value for my program. If desired, the input range could be limited or shifted by adding one or more fixed resistor(s) in series with the potentiometer. This would also reduce the sensitivity of the pot adjustment and help stabilize that last flickering digit on the DVM. I used a $1 Powerbank for my 5V supply. One advantage to leaving the range as 0-5V is that I can use the DVM & pot to check for full 5.0 V output. Less than 5V indicates a low 18650 battery in the Powerbank and time to recharge.

This is a companion quick & dirty hack to my thread which used these $1 DVMs as output display: https://picaxeforum.co.uk/threads/1-digital-voltmeter-becomes-one-pin-led-display.27594/

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