Low voltage on Duet3 6CH IO pins

e4d

Hello,

I have Duet3 6CH and only have 2.41V on IO pins when I put them "high". If I understand correctly I should have 3.3V. The pin is wired to an SSR relay and the voltage is too low to turn it on. I checked the voltage at the input of the relay.

Here's my config for this part :

M950 S0 C"0.io7.out" Q1000
M42 P0 S1

Do you have any idea why I have such low voltage ?

jay_s_uk

@e4d what pins are you wiring between?

e4d

@jay_s_uk I use the io7.out and GND pins of IO_7 connector

jay_s_uk

@e4d looking at the schematic the output ports are fed directly from the MCU so there may not be enough current to switch a relay (I believe typically only 3-5ma).
You'd be better off using a fan output.
Take 3.3v from and IO port and feed it through the relay to the out pin on a fan

dc42

@jay_s_uk said in Low voltage on Duet3 6CH IO pins:

@e4d looking at the schematic the output ports are fed directly from the MCU so there may not be enough current to switch a relay (I believe typically only 3-5ma).
You'd be better off using a fan output.
Take 3.3v from and IO port and feed it through the relay to the out pin on a fan

Most SSRs work with from 3 to 32V input, so for those types a fan output set to either VIN (which I assume is 24V) or 12V would be suitable. However, there are other alternatives:

If you are not using the Laser/VFD port you can use that. It provides a 5V signal level. Note, it is shared with OUT9.
The PS_ON output is an open-drain mosfet, so if you are not using it to control a power supply then you could connect the SSR - control terminal to it and the + control terminal to e.g. +5V from an IO connector. It's also likely that it would work with the + control terminal connected to the 5V_EXT_INPUT pin on the PS_ON/5V_EXT connector. However, PS_ON does not support PWM.

Gixxerfast

@e4d May I ask which SSR you are using as many, for example, Omrons are speced to at least 5V to switch.

Example:

e4d

@jay_s_uk I had success with your proposition, thank you !