16-channel relay board orientation help


New member

For context, I'm totally blind and normally determine headers and I/O ports by a combination of reading documentation, continuity/voltage tests, computer-vision interpretation and logical-guessing/trial-and-error.

After trying my usual techniques, I'm at a loss for two items on the 16-Channel Relay board and I hope someone can help me.

1. What is the 8-pin header perpandicular to the GPIO header and beside the dip-switches? Also, what is it's pin-out definitions?

2. What is the 3-pin connector (and pin-out) of the port beside the push-button.

Of course one of these ports is RS485 but unclear from anything I've read or tested which one it is.

Also, has anyone managed to get the push-button to function? I've tried various methods using python but no joy!

thanks and great board so far!


Staff member
1. The 8 PIN header next to the DIP switches is used in the factory for programming the on-board processor.
It serves no purpose in the field.
2. The 3 PIN connector next to the push button is the RS485 port.
It is duplicated in the upper left side of the board, but there it has only 2 pins A and B - no ground.
It is handy if you daisy-chain more than one card on the RS485 port.
3. The pushbutton goes to the processor. You have a command to read it.
The processor can interrupt the Raspberry Pi on GPIO26 (pin 37)

Let us know if you have more questions.


New member
Hello and thanks very much. Your description is very helpful. Also, I think you saved me from incorrectly applying voltage to the duplicated RS485 port. I assumed that the 2-pin connectors beside relay1 and relay16 were both for 5V external power (one power source for each bank of 8 relays) but now I've corrected my assumption. Am I right that the 2-pin RS485 connector is beside relay1 and the 2-pin connector for external power must be beside Relay16. This of course assumes an orientation with the GPIO header along the top.



Staff member
I would say the 2 pin RS485 connector is upper left, and the power connector is upper right.
We have about 15 cards with identical dimensions and identical connector layout.
So keep this in mind if you ever use any other of our cards from the Industrial Family.
RS485 has always 2 connectors, 2 pins upper left and 3 pins lower right.
Power connector is always upper right.
Pushbutton is always in the same position, next to the 3-pin RS485.
Inputs and outputs are left and right.
Nine LEDs are on the bottom row. Leftmost is power, the other 8 are signals.
When the card has 16 inputs or outputs (as is the 16 relay card) the LEDs are bicolor, multiplexed in software.