How do I install a heat bed relay with an ATX power supply?

[ex-egll]

Before addressing how to wire up the heater bed relay I would seriously consider upgrading the power supply. As you say the bed needs 30Amps. The extruder heater probably needs in the order of 3.5 Amps. On top of that you have 5 motors plus the controller board to supply, lets take a guess of 2.5Amps for that. We have a total of 36Amps, nearly 50% more than the P/S is rated for.

Now you might be lucky and get away with it, but one day Murphy will strike and all 5 motors, the heated bed and the nozzle will all turn on at the same time, that will probably be the time that the P/S throws its leads up in the air and says "I quit". If Murphy is having a real good day that will occur 15 hours into a 17 hour print job.

Even worse than the catastrophic failure will be little glitches that could occur when the heater bed comes on, it could just drop the voltage low enough to upset the controller board causing intermittent, and highly difficult to trace problems. These problems take the fun out of printing!

In conclusion, try for a larger power supply, or as an alternative you could use a second power supply, if the current (no pun intended) one is sufficient to bring the bead up to temp in a timely manner, to run everything except the bed as it will be isolated by the relay.

Good luck

[rhonal89]

What ex-egll said. Most problem people have is not enought power for their electronics.

Before addressing how to wire up the heater bed relay I would seriously consider upgrading the power supply. As you say the bed needs 30Amps. The extruder heater probably needs in the order of 3.5 Amps. On top of that you have 5 motors plus the controller board to supply, lets take a guess of 2.5Amps for that. We have a total of 36Amps, nearly 50% more than the P/S is rated for.

Now you might be lucky and get away with it, but one day Murphy will strike and all 5 motors, the heated bed and the nozzle will all turn on at the same time, that will probably be the time that the P/S throws its leads up in the air and says "I quit". If Murphy is having a real good day that will occur 15 hours into a 17 hour print job.

Even worse than the catastrophic failure will be little glitches that could occur when the heater bed comes on, it could just drop the voltage low enough to upset the controller board causing intermittent, and highly difficult to trace problems. These problems take the fun out of printing!

In conclusion, try for a larger power supply, or as an alternative you could use a second power supply, if the current (no pun intended) one is sufficient to bring the bead up to temp in a timely manner, to run everything except the bed as it will be isolated by the relay.

Good luck

[TehStranger]

Before addressing how to wire up the heater bed relay I would seriously consider upgrading the power supply. As you say the bed needs 30Amps. The extruder heater probably needs in the order of 3.5 Amps. On top of that you have 5 motors plus the controller board to supply, lets take a guess of 2.5Amps for that. We have a total of 36Amps, nearly 50% more than the P/S is rated for.

Now you might be lucky and get away with it, but one day Murphy will strike and all 5 motors, the heated bed and the nozzle will all turn on at the same time, that will probably be the time that the P/S throws its leads up in the air and says "I quit". If Murphy is having a real good day that will occur 15 hours into a 17 hour print job.

Even worse than the catastrophic failure will be little glitches that could occur when the heater bed comes on, it could just drop the voltage low enough to upset the controller board causing intermittent, and highly difficult to trace problems. These problems take the fun out of printing!

In conclusion, try for a larger power supply, or as an alternative you could use a second power supply, if the current (no pun intended) one is sufficient to bring the bead up to temp in a timely manner, to run everything except the bed as it will be isolated by the relay.

Good luck

What ex-egll said. Most problem people have is not enought power for their electronics.

My power supply has two 12v rails, both of which are 25A.

I assume the worst thing that could happen is the bed won't heat up properly.