Multiple relays on the skpang 4ch relay board

gistfile1.txt

You can switch multiple relays on the same was as single relays – it’s just a different value passed.

If you think of the relays as 1, 2, 4, 8 then it makes sense. Passing these values directly will turn on the relays singularly, something like
for relay in [1, 2, 4, 8]:
bus.write_byte_data(0×20,0×09,relay)
time.sleep(1)

will step though all the relays (this is what the test_relays script does).

If you want to switch multiple relays on, add the numbers together and use that. For example:
Relay 1+2 – 1+2 = 3
Relay 2+3 – 2+4 = 6
Relay 1+2+3 – 1+2+4 = 7
Relay 1+2+3+4 – 1+2+4+8 = 15
Relay 1+4 – 1+8 = 9
Relay 3+4 – 4+8 = 12
etc…

This should give you control of all 16 combinations. For reference 0/16 is all off, 15 is all on (anything higher than 16 will cycle back around).

Hope this helps!