Analog Potentiometer to Digital - Page 1
Forum section: electronics / beginners

author: Falcon69
author_rank: Super Contributor
timestamp: September 13, 2015, 05:34:22 pm
content: Hello,I have a potentiometer, 1W 2A, and I would like to change that out for a digital. There seems to be an input/output of 5volts to it.I would like to switch it out to a pushbutton type 7 segment LED (or crystal LCD Display)If that is too complicated, then what about just hooking up a Voltmeter, like one of the cheap ones on eBay (http://www.ebay.com/itm/Brand-New-Novelty-Voltage-DC-Display-0-30V-LED-Digital-Voltmeter-Panel-/121686593988?hash=item1c551611c4). I actually have one of these, and when I hooked it up, it only showed the voltage from 0-5v as the knob was turned, which was expected.Now I tried doing a google search for ways to multiply that readout to 0-100V, but could not find anything. If it can read 0-100v, then it would let me know the position of the potentiometer on a scale of 0-100, that way, I would know if the power rating was at 40%, 20%, etc.Is there anyway of doing this? I looked at items like (http://www.ebay.com/itm/DC-5V-12V-Digital-Potentiometer-Volume-Control-Board-Audio-Encoder-Switch-Module-/171875160897?hash=item28048ed341) but it will only do 0-84.I know I could hook up an Arduino to it and make it work that way, but that gets too complicated and costly for this project.Thanks in advance.

author: SeanB
author_rank: Super Contributor
timestamp: September 13, 2015, 05:40:46 pm
content: Grab one of the 0-100VDC ones off eBay and modify it. The voltage divider is taken off from the power supply side, so simply removing the power supply components and feeding in 5V that you have will operate the display. then you take the ADC input and use a lower value voltage divider, you might need to either select on test the resistors to get 0-100 on the display or use a 10 turn pot to set the ratio correctly.the 0-30V ones might work fine though, they probably are limited by the PSU as to input voltage range, so for 99c you can buy a few and try and modify it. The ones I got use a resistor and a TL431 as a power supply, with a separate resistor divider for the sensing, so they probably will do 0-100 as a 0-5V input to the ADC of the little PIC micro there.

author: Falcon69
author_rank: Super Contributor
timestamp: September 13, 2015, 07:20:50 pm
content: SeanBI think I've located the resistors for the voltage divider you speak of. It's hard to find them, because I can't see the other side of the board, there's a 7seg LED blocking the other side.On the inputs, there are three wires, black, red, and green.The Black and red connect to the voltage, and the green wire connects to the wire I want to sense the voltage on.From that green wire, it goes into a 100K (104) resistor, then from there into a 3k (302) resistor, then it goes to different stuff. There are vias as well.Here's a pic. Sorry, my camera is pretty bad.SO, would i just need to change the 3k to a value 20x? So change it to 60k? (5volts in x20 = 100volts)Would that display a range of 0-100 then?

author: Falcon69
author_rank: Super Contributor
timestamp: September 13, 2015, 07:52:38 pm
content: oh! I found the schematic for it.R5 on my board is 104 (100k) and R4 is 302 (3k)