Connecting additional SSR's

jens55

I would like to hook two SSR's to my Duet2 wifi. I currently use the bed heater output to activate an SSR to power the line voltage bed heater. The E0 heater output is used to power the hot end and E1 heater output is used to power the LED lights for the printer enclosure/ambient light. Fans 0 and 1 are used for fans, fan3 is still open and could be used to power an SSR but that leaves me with one additional SSR that I still need to control somehow.

Short of adding a Duex5 expansion card, is there any other way of controlling this last SSR?

Phaedrux

https://docs.duet3d.com/Duet3D_hardware/Duet_2_family/Duet_Expansion_Breakout_Board

Or the expansion header pins directly, though it would be good to know what you intend to use the SSR for, in case there are any catches.

https://docs.duet3d.com/Duet3D_hardware/Duet_2_family/Duet_2_WiFi_Ethernet_Hardware_Overview#inputoutput

The outputs on the expansion connector are active low with 3.3V signal level.

jens55

@Phaedrux, to control my bed heater I have an external box that has an SSR in it and a regular 120V output connector. The bed plugs into that. This external box has a total of 3 SSR's in it, the one that switches the heater plus two spare ones. I want to be able to control those two additional SSR's. They could be used for pretty much anything 120V driven .... for example an enclosure heater.
I could easily do this with a Duex board but I was wondering if there is another way of doing it that is less involved.
I have done a few tests and am thinking that I could use +5V on the expansion header and three heater pins to control the three SSR's. I am mostly concerned with having a +5V signal on the expansion header pin when the output is not active (ie not pulled low). Using 3.3V for power is not enough to turn on the SSR.
Due to my setup, all the SSR's would have to be controlled via the expansion header which means I would move the connections for the bed heater to the expansion header (from the bed heater output that is currently used)
The current required to power the SSR is less than 5 ma so that should work just fine.
Is there anything I am overlooking? Are the heater output pins on the expansion header 5V tolerant? Has anybody done this before? How likely am I to kill the Duet2?
Another option is using an SX1509 port expander (if the output is 5V tolerant .... edit: apparently 5.5V tolerant)

dc42

@jens55 you can also use the PS_ON pin to control a SSR is that pin is free.

jens55

@dc42, I looked at that but didn't find any specs. I just looked again and it would seem that the pin is good to 30V so should work. I will run some tests today.
Could you confirm if the heater output pins on the expansion header are 5V tolerant?

jens55

Using the PSON pin worked. The only thing I have not been able to do is to make the output a PWM output.
No matter what "S" setting I try, the output is either on or off.
I use M950 P0 c"PSON" Q100 for configuring the output and I use M42 p0 S? for activating the pin. Any value of S under 0.5 will turn the output off, any S setting above 0.5 will turn the output on.

The SSR that is controlled by the fan2 pin sort-of works for PWM but behaves rather odd. I have a light hooked up for testing and while the light intensity is controlled correctly, the brightness flips every few seconds between a dimmer and slightly brighter mode.
I also tried a switching frequency of 10Hz.

jens55

After more thorough reading of the Duet2 documentation, I found out that the pson pin does not support pwm so that answers my first issue. I am still curious about the second issue (alternating dimmer/brighter pwm output) although truth be told, it probably isn't an issue in the great big scheme of things.