Use extern powersupply to heatbed with Melzi board

Hi all.

I have a Mk3 Heatbed wich can be supplied with both 12 and 24 volts. My problem is, that when running on 12 volts it can get higher than 97C due to low room temperature (we are in the middle of the Nordic winter). I would like to run it at 24 volts besource I have testet it externaly with 24 volts and then there is no problem with getting higher temps.
So I need help to make system where my Melzi board controls some sort of a relay with the board heatbed output.

Happy printing
Torben

ooUUps.

I missed a "not" between can and get. Correct sentense is: ....when running on 12 volts it can not get higher than 97C.......

Sorry

Solid state relays work well for heated beds. You can then use an completely separate power supply. I use [www.ebay.co.uk] You just need to connect the relay input to the bed output on your board. Then the heat bed to the power supply through the relay.

You don't need any extra electronics as long as the bed current is not too high for the Melzi. Just disconnect the bed from the positive terminal on the Melzi and connect it to 24V. Link the 0V from both PSUs. The MOSFET on the Melzi just grounds the other bed terminal to turn it on.

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[www.hydraraptor.blogspot.com]

Thank you both. I will try your options.

Happy printing
Torben