Noisy Trace Mystery

Other Hardware Robotics
1

I have a mystery on my hands. The highlight trace is the step pulse for the stepper motor driver ( DRV8826 ). When I attach the O-Scope probe to the stepper test point ( The via on the trace ) it runs wild!!!! Then when I move my hand it also causes the stepper motor to run eraclicy. Denping where my hand is it runs slowly or very violent steps!! Even with the probe disconnected.

Does anyone have a clue what's causing the weird behavior?

Noisy_Step_Trace_5ce41328d65c055115f485d515999dd4e413e997
Noisy_Step_Trace_5ce41328d65c055115f485d515999dd4e413e997451×520 88.6 KB

The step pulse is generated by the logic controller (Adafruit Itsy Bitsy 32U4 3V GPIO Pin 5 ).

2

It appears you have a bad connection. Check the solder and re-flow the solder in the problem section with your iron. If that does not fix it the next thing I would do is add a jumper wire, easy since it is through hole, to bypass the trace. If your plate through is bad you may have to jump to the top side.

3

That via is where I soldered a single-pin header to connect the probe to.

Here is the code that drives that pin::::

digitalWrite(Busy_Pin , true);
    digitalWrite(Step_Pin , !digitalRead(Step_Pin));
    Serial.print(" \t Step Pin = ");
    Serial.println(digitalRead(Step_Pin));
    delayMicroseconds(Delay);

I also checked all the soldering and they are perfect.

Could I have blown the controller? It seems to be working OK because the print statements are printing the correct info.

4

I have similar looking boards. They are really cheap with NO plated through vias. The boards were all made the old fashioned etching method.

5

OK, I will check it out. I will place a jumper from the controller to the driver.

I use PCBWay for my boards. I really like their workmanship and the quality of the boards.

6

That is a clear sign of an open, floating input.

7

OK, I soldiered a jumper by passing the trace, but it did not fix the problem.

Is there any else I should check?

May be I blown the contloer chip ( Itsy Bitsy 32U4 3V ). I have ordered a new one.

I will inform you if the new one works.

8

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.