Powering System Safety Relay - 3.3V Expansion Pin RRF3 [Solved]
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Can someone help me with a proper M950 and M42 code that will allow me to toggle on/off the 3.3V [exp.3] on the Expansion Header of a Duet Wifi controller? I would like to control an external relay from this pin.
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you mean the 50 pin connector from the duet ? without a duex or another card is connected?
and which pin you mean ? i see there no exp.3pini think you mean the endstop 3 (pin 9) the documentation saythe endstop connectors on the expansion board and are input-only -
M950 P0 C"exp.heater7" ; Expansion connector pin 31.
Then use M42 P0 S1 to switch on, or S0 to switch off.
3.3V only!!! Relay? Maybe consider either snubber diodes or a transistor on the output pin before the relay.
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Thanks Danal,
The code worked well but for some reason my relay isn't working. Can you recommend another pin and code to try if I were to use a 24V relay which matches my input power on the Duet controller? My E1 heater output is available.
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Output pins on expansion will only ever be the logic voltage. 3.3V in this case. If the relay is not specifically an ultra-low-current 3.3V relay, it will not work. It will need a transistor or similar.
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@code7 said in Powering a System Safety Relay with 3.3V Expansion Pin in RRF3:
Thanks Danal,
The code worked well but for some reason my relay isn't working. Can you recommend another pin and code to try if I were to use a 24V relay which matches my input power on the Duet controller? My E1 heater output is available.
What relay are you using? Is it a barebone relay or a relay module like this one with some electronics on it? https://www.amazon.com/ICStation-Optocoupler-Trigger-Development-Arduinoo/dp/B07P73PHQY
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@zapta What relay are you using?
This is the relay from amazon that I am using: https://www.amazon.com/3V-Relay-Module-Optocoupler-Development/dp/B01M0E6SQM
Product Data Sheet: https://images-na.ssl-images-amazon.com/images/I/81SV55x7wbL.pdf
If you have a suggestion for another relay or relay/transistor combination I'll try it.
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It looks like the 3.3v output pins on the header are only capable of about 20mA. I'll use an SSR.
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The relay to which you linked says:
Trigger Current: 3mA
That should be fine, if you pull the jumper and power the relay separately.
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@Danal said in Powering a System Safety Relay with 3.3V Expansion Pin in RRF3:
That should be fine, if you pull the jumper and power the relay separately.
Exactly. GND to ground. VCC to 3.3V supply and IN to the 3.3V digital output that can drive at least 3ma.
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