The board comes in two variants, the -b suffix has bigger FETs.
- PCA9685 PWM chip.
- Each channel drives a N-channel mosfet.
- Note when switching a load with an N-channel mosfet, the load is wired with its positive directly
connected to power and the mosfet will switch the negative terminal of your load.
- For ease of hooking up, each channel has a power and a switched connection.
The small fets can handle 1A each. Running a total of 16A through the whole board will heat it up a bit, but should still work. Slightly more than 1A is permissible, provided it doens't last too long. But keep in mind that electronics works on a different timescale. "a second" Is already a very long time for such a small component.
The big fets can handle 5A each. But running 80A through the whole board is going to heat it up beyond permissible limits. Again a bit more for a short period can be permitted, but timescale of "a few milli seconds" and not "a few seconds".
Bottom edge has outputs 1-8, each with a <output> <V+> . Each is marked as such on the back of the PCB, as the front was full with components.
Top edge has outputs 1-8, each with a <output> <V+> . Each is marked as such on the back of the PCB, as the front was full with components.
The right edge of the PCB has 6 connections: GND, V1, V1, GND, V2, V2. The power connections are separate. This alows you to run one side of the PCB at a different voltage than the other side. Say 5V on V2 for the top edge of the board, and 12V for the bottom edge. There are two Vx connectors to make it easy to connect one powersupply by looping a sort wire from the second V1 to V2.
For full documentation see the PCA9685 datasheet.
To initialize I
- set register 0xfe to 5
- set register 0 to 0x20.
Now the chip is initialized and will do about 1500Hz PWM