I'm still in the process of testing everything on this SLO-100 PCB before i drop it in and start wiring it up. I just ran across another issue with the channel switching supply. I think I've solved the issue, but not sure if I did it the correct way. I am familiar with simple voltage dividers, but the channel switching circuit seems to have 2 voltage dividers that alternate with the position of the channel switch (toggle or foot). I attached an image of the circuit below. The more I look at the circuit, it seems the less I understand it. Supply voltage is 6.3vac. I noticed when the switch was open and the top leg was high, LDR2 & 3 had 1.88vdc on them. That is fine, but when the switch was closed (top leg grounded), LDR1, 4 & 5 had only 1.76vdc on them. As a result, these 3 LDR's had considerably higher resistance. I wanted to balance these out, so here's what I did. I removed R63 and subbed in my resistance decade box. I started at 33 ohms and dropped 1 ohm at a time, switching back and forth until all the LDR's got the same voltage. The final resistance is 22 ohms and that results in 1.85vdc on all of them. This drives the LDR's at approximately 10mA and the resistance of all the LDR's is less than 50 ohms. I'm real happy with this, but I don't know if the way I achieved it is correct, or if I'm asking for problems down the road. When I lowered R63, was I supposed to have raised another resistor to compensate? Lowering the resistance of R63 also resulted in a 20mA increase in current draw for the entire circuit.
Just a side note: I don't have any indicating LED's connected yet. I'm not sure if I ever will.
Topic: Tweaking voltage dividers (Read 1586 times)