Getting an active high relay to work.

nmsmith89

I'm currently setting up a Duet 3 Mini 5+ and I bought a 5v relay module to use the 5v Meanwell PSU to switch the 24v PSU on/off. I just realized that I bought an active high only relay before realizing that the PS_ON pin is active low.

Am I pretty much screwed and should buy a new relay module or is there a way to get it to work?

I did read somewhere that a 220Ω resistor between EXT_5V_IN and PSU_ON might make it work but I'm not really sure.

On a side note do I wire from the 5v PSU to the EXT_5V_IN pin on the PSU_ON header as well as the Neopixel header if I'm also using LEDs?

Thanks in advance for your help!

engikeneer

@nmsmith89 you have two options...

Option 1 - assuming you're using one of the relay modules, wire the supply and control lines on the relay module to 5V, then wire the ground pin to PS_ON. This is how I do it on my Duet WiFi.

Option 2 - I believe it was on the road map that you will be able to invert the operation of the PS_ON pin. Was planned for RRF3.2 but I can't find it in the docs so might have been pushed back...

So I'd say go for Option1 for now

On the neopixel header, I don't have D3 Mini, but believe you can take the neopixel supply from the Duet board if you are using an external 5v supply to power the board (the internal 5v regulator isn't powerful enough)

nmsmith89

@engikeneer

Option 1 - assuming you're using one of the relay modules, wire the supply and control lines on the relay module to 5V, then wire the ground pin to PS_ON. This is how I do it on my Duet WiFi.

Thanks! That sounds like a plan! And PS_ON can handle being a ground?

On the neopixel header, I don't have D3 Mini, but believe you can take the neopixel supply from the Duet board if you are using an external 5v supply to power the board (the internal 5v regulator isn't powerful enough)

It's confusing because the Neopixel header has a "5v in" pin and not a "5v supply pin" like I would imagine. So I just assumed you run 5v to the LEDs from the PSU. But then what the heck is the second 5V_EXT_IN pin for? I don't think you power them from the board because I don't even see a 5v out pin that isn't attached to something else. There isn't really any documentation as far as I could find. If I had to guess I would say the second 5V_EXT_IN pin that's on the Neopixel header just goes unused but I have no way of confirming that right now. The only way it really makes sense in my head I guess is if that pin was really supposed to be 5v out and not in.

Update

I found the documentation! It wasn't linked from the other documentation so I had to search for it. Here is what it says:

Connect the LED strips to the 3-pin connector labelled NP_LED.

Connect the GND pin of the LED strip to the GND pin on the Duet NP_LED connector.
Connect the +5V pin of the LED strip either to the EXT_5V_IN pin of the NP_LED connector, or to an external +5V power supply.
Connect the data input line of the LED strip to the NEOPIXEL_DO pin of the Duet.
You will need to supply external 5V power to the adjacent 5V_IN connector, unless you connected the 5V line of your LED strip directly to an external 5V supply. The 5V regulator on the Duet 3 Mini is rated at 1A total and cannot be used to power LED strips.

The maximum supported number of Neopixel LEDs in a strip is 60.

So that pin can also put out 5v from the other 5v input. I guess the pin name is just confusing.

engikeneer

@nmsmith89 I believe that the PS_ON pin is quite robust (would defer to someone else who knows for actual ratings). @Phaedrux?

As I say, that's how I use it on my Duet Wifi (and have been for a year) to drive four 30A relays (two twin-modules) and has been fine for me. I would assume that the D3Mini would be similar/the same

nmsmith89

@engikeneer

This may sound like a stupid question and I think I'm just psyching myself out and overthinking it but I just want to make sure i have the wiring right...

So on the external supply header 5V_EXT_IN goes to the 5v+ and control of the relay AND 5v+ on 5v PSU. PS_ON to ground on the relay. GND on header to ground on 5v PSU. Does that sound right? I can draw it out if it's too confusing.

engikeneer

@nmsmith89 that's right

nmsmith89

@engikeneer

Thanks for all your help!