Problems with PSU shutting down after heat bed reaches temp

OK, so I self resolved the other topic, but I'm not getting anywhere with this one and I'm a bit stumped. If I have the heated bed running and shut it off through the Pronterface console, its shutting down the entire PSU. 460W PSU with 2 seperate 12V 15A rails. Should be more than enough to handle both a hot end and a heated bed. The second the thermistor says the bed is at temp and starts dialing back power, the whole PSU craps out. So if I set bed temp to 60, it will run until bed temp returns 60 and then shut off. If I set it to 110, it will run the whole way up to 110, but still shut off when it reaches temp. Its as if a breaker is tripping in the PSU, although I dont reset anything inbetween. Simply shut off power switch and flip it back on.

During the bed heat up time, I have no problems running the hotend as well.

I'm thinking about trying to drive both hotend and bed from just one of the 12V rails too see if it solves anything. Or at least gives me some more insight. 1 - 15Amp line is pretty close to pushing it though isnt it?


any thoughts?

Thanks!

JW

Josh

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Josh

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//Prusa / RAMPS_1.4 & ATMega_2560 / Slic3r > Pronterface > Marlin / Luck
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So I've managed some more testing and reconfiguring and rethinking about the setup. I've unhooked one of the 12V rails and ponied off of the other one. Bed, nozzle and motors all worked and get no more shutoff from the bed reaching temp. When I get some free time, I plan on swapping out the 12V line for the other 12V line and see if I still get a working config. If it doesnt work, then there must be a problem with that line. If it does still work, then the RAMPS board most likely does not like the idea of having two seperate 12V sources and something is shorting out. I suppose its the equivalent of trying to use two different PSUs at the same time but mine is streamlined into one PSU. For reference this PSU came out of a server and was running two Xeon chips, hence the 2 seperate 12V lines. I feel like this will ultimately be the answer at which point I guess I'll be hunting for a new PSU since 15A is a little too close for comfort for me. I'll find one that has a single 12 with 20A.

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Josh

//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//Prusa / RAMPS_1.4 & ATMega_2560 / Slic3r > Pronterface > Marlin / Luck
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Hey Josh,

Maybe I missed it in your post, but what have you done with your sensing line on the power supply? Sometimes these types of power supplies salvaged from computers can be pretty particular about the loads they receive. That makes me think that you PSU is happy with the load from the bed and then when it reaches temperature, there is no more load and then something internally in the PSU tells it to turn off.

Hopefully this can help.

bdc
~Stay Calm Out There

You didn't miss it cause I didnt post it!

I've got a 10Ohm 10W resistor in the sensing line. I still havent taken the time to test theory against the other 12V rail yet. To be honest, its working on one right now (even at only 15A) and I've been having too much fun playing with the addition of a heat bed! Maybe this weekend I'll have time to swap it over and see what happens.

I'll update all when I get some insight. Its good documentation for someone in the future at the very least.

JW

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Josh

//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//Prusa / RAMPS_1.4 & ATMega_2560 / Slic3r > Pronterface > Marlin / Luck
//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++