Help with nucleo board and pca9685 servo board
- June 2, 2023
- 3 replies
- 2852 views
Hello everyone,
I came here looking for help : I'm doing a project for an intership where i have to create an hexapod robot basically from the ground up, with particular interest in the electronics and programming part.
As a main microcontroller, we are using an STM32 Nucleo L476RG, where we plan to pilot 6 of our total of 18 servo-motors, and then we plan on piloting the rest of our 12 servo-motors using our Adafruit pca9685.
While using the datasheet, and different videos to learn how to use the pca9685 correctly, we ran into 2 main problems.
One of them is that the top part of the board, so the slots where you input your ground and your V+ to power the servo-motor pin row, isn't correctly connected with the servo-motor V+ row.
adafruit.PNG (275.16 KiB) Viewed 6 times
We tested to see the continuity with a multimeter, and it wasn't linked, while the ground parts all were, logically.
Which means that we can't power our servo-motors using the input designed for it, and we either have to use the V+ found on the left of the board, or directly attach our power to the V+ row of pins on the bottom.
Our second main problem is the PWM signal output amplitude is extremely low, around 5 mV, which we can't use of course. We tried looking up online why the output is so low, but haven't found the answer unfortunately.
Attached you'll find a picture of our results using an analog descovery oscilloscope. On the right side of the screencap we can see the scale (10 mV/div). We do manage to get our period of time correctly though.
So basically, problem 1 is we can't input our V+ where we should, because there's no continuity between the V+ input and the servo-motor V+ row, and problem 2 is our PWM signal amplitude is extremely low, so useless.
I tested this in 3 different pca9685 boards (clones of the original) and none of them worked.
Hopefully everything is clear, and someone can manage do lend a hand.
I can give more info in the comments.
Thank you very much!