Trouble shooting fluctuating readings from Analog sensors.

N

nicnut

Well-known member
Hi,

I have a Teensy project that has been working really well since I finished it in 2018. Recently I am having some issues with it and I am having a really hard time diagnosing the issue.

This project uses 2 Teensy 3.6 microcontrollers. One of them is connected to around 13 analog sensors, and their readings need to be consistent, and mostly this has been fine till recently. Now, some of the sensors are a little off every time I turn on my device. Each analog sensor is connected to 3.3 volts for power, ground (both from the teensy) and connected to an Analog input on the Teensy. if I barely touch the 3.3v wire it changes the readings of one of the analog sensors. I have a feeling there might be a loose connection somewhere, but I have unsoldered and resoldered as many connections as I can and the problem persists.

Is there a way to put a capacitor connected to the 3.3V wire? And if so, should the other side of the capacitor be connected to the ground wire? What size capacitor should I use? Or are there any other suggestions to resolve this?

I know I could take the whole thing apart and start over, maybe can a newer Teensy, but that would be a lot of work.

Thank You.

Nick
 
Which sensors? How long are the wires? Try something like 100nF (value not critical) between 3.3V and GND directly at the sensor.
 
Those are passive devices, but the outputs are fairly high impedance. Better to add ~100nF from signal (wiper) to ground (near the Teensy), decoupling isn't so useful for a passive sensor. You shouldn't be able to influence the 3.3V wires like that, I wonder if something else is the problem - like you changed to a class II power supply instead of a class I (grounded)?
 
Hi @MarkT Thanks for your input. I think you are correct in suggesting the cap near the Teensy is between signal and to ground.
Definitely something else is the problem that I can't discover. I have a feeling there is a bad connection somewhere. I am trying to find it, and am resoldering any sketchy looking solder joints. The problem is reducing, but it's still persistent. The fact that it moves around to different sensors has me thinking it's a power or ground issue, because all the sensors are connected to power and ground.
 
You must log in or register to reply here.
Back
Top