OP
OP
Check the 3.3V line coming back from the Pi - it’s unused on the Pico board (outside of a capacitor).
Reef-Pi Controllers: New all-in-one with power bar, and the original Pico
- Thread starter theatrus
- Start date
- Tagged users None
Check the 3.3V line coming back from the Pi - it’s unused on the Pico board (outside of a capacitor).
dmolavi
Well-Known Member
I saw that on the schematics. Where is it exposed on the Pico?
OP
OP
Unfortunately just the pin on the header and the adjacent 0603 capacitor. Any 3V3 stuff on the base board comes from a different regulator as the one on the Pi is fairly weak.
dmolavi
Well-Known Member
what's the 'safest' way to tap into this? (I'm at work now, don't have my board in front of me)...just solder a white-wire to the bottom of the board at either (physical) pin 1 or 17?
For < $1@, I'm gonna pick up a couple of USB connectors from Arrow, as well. I tried pulling apart an old cable last night, but the strain relief section was still too long for the clearance I have inside my enclosure.
- Joined
- Dec 16, 2018
- Messages
- 1,189
- Reaction score
- 2,826
If by equipment you mean outputs from a ULN2803, then no you would not see voltage.
The ULN2803 sinks current to ground. When its input is taken high, its corresponding output is then grounded which completes the circuit triggering the corresponding relay.
The ULN2803 sinks current to ground. When its input is taken high, its corresponding output is then grounded which completes the circuit triggering the corresponding relay.
dmolavi
Well-Known Member
Frack so the DB9 can't source current? Even if the GPIO pins are high? Or do I need to "reverse" them in the output configuration?
dmolavi
Well-Known Member
LEDs to indicate on/off status
dmolavi
Well-Known Member
The pico board schematics show that it should be able to source it, if I'm reading it correctly.
- Joined
- Dec 16, 2018
- Messages
- 1,189
- Reaction score
- 2,826
Sorry, im not that familiar with the pico board, its using a different configuration than the uln2803 for outputs.
Yes it appears that you can sink or source current...try checking the reverse box in reef pi
OP
OP
The pins route to an N channel MOSFET, they can only sink current at the DB9. You can still use LEDs attached to the DB9, just connect the cathode and supply voltage at the anode side (don’t forget a current limiting resistor). You can wire in parallel with the ADJ relay pack as well.
dmolavi
Well-Known Member
What do you mean by connecting the cathode and supply at the anode side? Right now, I have the anodes connected to the DB9 GPIO pins and thr cathodes to ground through a resistor.
Should I go from the 12V pin on the DB9 to each anode then to the DB9 GPIO pins from the cathodes?
OP
OP
dmolavi
Well-Known Member
Haha yeah. I used a 470ohm resistor..should be enough but I'll double check
dmolavi
Well-Known Member
To clarify...I have the LEDs wired in parallel, each with it's own resistor.
OP
OP
Are you using a ADJ strip as well? Each LED should have its own resistor, and in parallel with the relay on the ADJ strip, if applicable.
dmolavi
Well-Known Member
No ADJ strip. It's basically just an array of 8 LEDs.
I'm thinking that the better way is to do two sets of 4 LEDs in series with a 180ohm resistor for each set...
dmolavi
Well-Known Member
@theatrus - Before I go and re-wire all this...would this be the correct setup? Resistors are 500 ohm. Instead of going to ground as in the diagram, each cathode would go back to a DB9 pin.
Or would this be a better solution (the connector on the bottom is the DB9...uses 200 ohm resistors, and the two lines to ground are just to complete the circuit, wouldn't need to be on the actual board, correct?):
Regardless of which is better/more correct, either would allow for each LED to be individually switched on/off via the 'equipment' page in Reef-Pi? (I'm not using an ADJ...these are status only)
I think the first one, although I don’t know why, but better circuits have more passives 
Similar threads
