Voltage Divider

January 13, 2024, 11:32

beatlejuice1337

Hey Folks, trying to copy parts of the kinowheels.com project and attach it to a pico instead of an Arduino mega. So far i replicated just one of the voltage divider and attached only one of the outs of the encoder to my breadboard. Yet I did not added the pico as i measured ~5V (encoder HIGH) on the tap where it should be connected. Is this due to not having a load (no pico, just volt meter) attached? When i add another 20kOhms between tap & ground i get desirable 2.5V, but i don't know if i'm doing it right. Appreciate any help!

oops.se

As you haven't described the voltage divider with data/technical information that can be calculated on ... So please provide schema or technical data.

beatlejuice1337

schematic https://shorturl.at/bivH3 - those are 10kOhms resistors project: https://shorturl.at/aLP45

oops.se

Is this due to not having a load (no pico, just volt meter) attached? No a multimeter/volt meter has a very high inner resistance (in multiple mega ohm range) as does a Arduino and Pico also have. Raspberry Pi Pico is a 3,3 volt device. So that means you have to change 5v to 3,3 v. And the voltage divider can be calculated with https://ohmslawcalculator.com/voltage-divider-calculator But a voltage divider with the same value of the resistors is has half the voltage in the middle point, but I think that you have already figured that out. So with a Raspberry Pi Pico should the desired voltage be 3,3/2 = 1.65 volt. And after reading link it just uses edge detection (RISING) so that should work with the current voltage divider and changing the supply to 3,3 volt.

beatlejuice1337

this is what i did - not sure if it's right, at least the magic smoke stayed inside: on the breadboard i linked, you can find row 28. from there i added 20kOhms and pulled that to ground. the highs/lows from the encoder get recognized, but if this is electrically sound, i'm not able to tell yet. - I'm supplying the Pico (usb/vbus) & the encoder via pico with 5V.

oops.se

I wouldn't use 5 volt for the encoder. There is 3,3 volt available on the Pico and I would use that the feed the encoder/voltage divider as the Pico pin isn't 5 volt tolerant. This is good practice to do so.

beatlejuice1337

The encoders voltage range is 5-24V, so i cannot go below 5V to drive this kinda of encoder. It's not a poti style rotary encoder. - LPD3806-600BM-G5-24C is the part.

oops.se

Ok, that make sense