Connecting a DA SSR

[Nxt-1]

I am in the process of wiring up an very high powered AC heated bed, using a SSR to control it. The printer originally came with the DC bed connected to the Duet's GND terminal and the 12V from the PSU. I am wondering whether I reuse this wiring to connect my SSR. Or is there a good reason to find a place in the delta towers to run an extra wire connecting Duet bed + and SSR + ?

Below, a simple drawing of how I plan to wire it.

[fcwilt]

Hi,

If you wire it as shown the bed heater will always be on - I cannot imagine that is what you want.

Check the normal bed heater connector on the Duet.

One terminal is marked with a "-" symbol, the other with a "+" symbol.

Connect those to the SSR control inputs, observing polarity.

BTW what's a TCO?

Frederick

[Nxt-1]

@fcwilt said in Connecting a DA SSR:

Hi,

If you wire it as shown the bed heater will always be on - I cannot imagine that is what you want.

Check the normal bed heater connector on the Duet.

One terminal is marked with a "-" symbol, the other with a "+" symbol.

Connect those to the SSR control inputs, observing polarity

Why would the heater be always powered? The bed output of the Duet still opens and closes the circuit I imagine.

BTW what's a TCO?

TCO stand for thermal cutout, basically a temperature triggered fuse.

[sigxcpu]

Mark you different GNDs to be more clear.

[Nxt-1]

@sigxcpu As requested

[dc42]

Yes, that will work.

[Nxt-1]

@dc42 said in Connecting a DA SSR:

Yes, that will work.

Is there any consequence or disadvantage wiring it this way?

[dc42]

None that I can think of.

[fcwilt]

@nxt-1 said in Connecting a DA SSR:

Why would the heater be always powered? The bed output of the Duet still opens and closes the circuit I imagine.

Because the way you had it drawn originally you had the - terminal of the SSR connected to a terminal on the Duet labeled GND. You had the + terminal of the SSR connected to +12, thus the SSR would be on as long as the power supply providing the +12 was on.

Now you have changed the diagram to show using the BED- terminal which is NOT ground. Connecting that way will work.

And as mentioned if it makes things simpler or clearer you can connect the BED+ terminal to the SSR + terminal.

Frederick