powering heated bed without relay
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Hi community!
I've recently switched from a ramps 1.4 to the duet 2 ethernet. My main voltage is 12v but the heated bed is 20v and has previously been powered through a relay as I was told that the ramps didn't like to handle 20v. Now I wonder if it is possible to connect the bed - to the corresponding connector on the duet 2 and the bed + directly to the 20v power supply (and leaving the onboard bed + connector empty) and therefore omit the relay completely?
Of course the - of my two power supplies are connected to ensure that they have the same level.
Sorry if this is a stupid question. I only have some very basic knowledge of electrical engineering and therefore prefer to ask before I'm going to fry something...
Thank you very much in advance! -
IMHO, I would continue to use the Relay or even better upgrade it to an SSR.
If it is a relay, that thing is going to click like mad!HTH,
Paul. -
That'll be fine, its low side switching so you can wire the bed like you describe and connect the two psu grounds together with a wire that can handle the power for the bed. (asuming the bed is within the current spec of your duet)
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The Duet allows you to use a separate PSU for the bed heater. Connect the negative output from your bed PSU to the ground side of the VIN terminal block, along with the negative output of the main PSU. Connect your bed heater between the positive output of your bed PSU and BED- on the Duet. Leave BED+ not connected.
The maximum recommended bed heater current is 18A. Above that, use a SSR.
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Thanks for all your answers. Tomorrow when I have time I'll rewire the bed this way. The 18A are no problem as the PSU can't even supply more than 15A and measuring with my multimeter yields approximately 12.5A for the heated bed. Therefore I'm going to get rid of the (annoyingly loud and frequently clicking) relay.
