My circuit has 3 sections. The supply is 9V.
This goes to a regulator (5V), another regulator (3V) and the 9V is connected directly also to a BLDC. Now, when I start the motor (this is done in brake with braking action), I see some curves, something like capacitor charging up. I have 2000μF aluminum electrolytic cap in the voltage rail as well.
Even when I remove that, I see these spikes. So there must me some parasitic caps that seem to be charging and discharging. I then inspected the regulator o/p. Both the regulator o/p inductor showed immense noise (the voltage transients was almost 1.5V, and it was existing throughout the motor operation).
The circuitry:
The regulators are:
The images in order are:
- 9V- 5V regulator
- 5V to 3.3V
- LiFePo4 charger chip
- Controller to BLDC circuitry
How do you want me to show the layout/PCB? How can I sort this out? Is the motor action causing spikes back into my circuit to make the ground noisy?
Best Answer
Andy is right we need more info but if I had to take a shot in the dark it's back EMF from the motors (highly inductive load) and you need flyback (or sometimes called snubber) diodes to dissipate this. Read this pdf as it explains it in greater detail:
http://www.eao.com/global/en/Downloads/technical_articles/EAO_TA_Inductive-Loads.pdf