Hey, all. I'm trying to use two BJTs to switch between two LDRs (8k-135k) as input to an Arduino, as below (R3 and R5 are LDRs, analog input connects at node 4):
However, the voltage at the digital output has a significant impact on the voltages at the LDR voltage dividers, and so on the output. What am I missing here that's interacting with those? I assume it has to do with the load that the BJTs are placing on the voltage dividers, but I'm not sure how to mitigate that.
Any other thoughts on the design (especially choice of resistor values; most were pulled out of my rear) would be appreciated, with a couple caveats:
1) I could do this easily with MOSFETs, but I have a ton of small BJTs lying around, and I figure I should use them for something.
2) I do need to use the digital out to switch between two LDRs, because ultimately there will be 8 LDRs and only 4 analog inputs.