Additional power supply for heatbed

[KLucky_13]

Hello, I have a 3Drag/K8200 DIY 3D-printer and I am currently busy with installing a mosfet controller to fit a additional power supply since the original supply is not good enough to get enough heat to print ABS.

I think I'm almost there to fit everything together, I just want to ask a few questions before blowing anything up (since I am not that great with electronics):


*First of all, I found 3 power supply's laying around and I'm wondering of any of these 3 is good enough to make this setup work:


First one is a power supply of a pc:
12v 32A = 380 watt
second and third one is a power supply of an old laptop:
20v 6A = 120 watt
and
19v 4A = 76 watt (which will be not enough a assume)



will any of these 3 perform good enough for this situation? (the bed is 80 - 90 watts)


*Second question is the wiring, I drew in paint what I understand of how this mosfet has to be wired (I can be completely wrong, but this is what I understand with my basic knowledge about these things):





So on the control-board both left pins are positive and both right pins are negative, correct? Weird thing is, on the signal input is no + or - written (at least weird for me, probably this is logic for someone who understands :-))


*Final question:

There is a message on the back of the mosfet-printboard:



what does this normal or inverted means? I'm not that good with this kind of stuff (that's the reason i bought this printboard and did not assemble it myself). I assume I have to solder the "normal" jumper.


And by the way, if you look closely, the normal "jumper" looks like it is already connected to each other..



Thanks for your time ;-)

[old man emu]

I'll only comment on the power supplies.

If the power supply from the computer is an ATX one, go for that. You want amps at 12V.

Old Man Emu

[KLucky_13]

Thanks for your reply, yes it is an ATX. Just out of curiosity, why should I choose for this one? I mean by that why do I want 12v instead of 24?

I've seen allot of people (on another forum) using this power supply:
24V 4,5A 100watt
http://www.reichelt.de/Schaltnetztei...r=SNT+MW100-24

or even this: 24V 13A 380watt
http://www.reichelt.com/Power-Device...W=1&OFFSET=16&

[LambdaFF]

My guess would be that the most important in heating is amperes because you know... R*I² ? ;-)

[old man emu]

Thanks for your reply, yes it is an ATX. Just out of curiosity, why should I choose for this one? I mean by that why do I want 12v instead of 24?

1. The board that controls your steppers, heaters, fans etc, takes the input from your power supply and reduces it to either 12V or 5V depending on which part of the board it is going into. So supplying 24V as opposed to 12V is no advantage. As LamdaFF says, it is the amperes that count. You should be looking at 16+ amps to run things.

I can post a link to the instructions for converting an ATX PSU to a power supply for your machine if you like.

As for heating, I installed an automobile horn relay between my PSU and heated bed to get more amps to the bed. The relay is switched by the heat bed control on my RAMPS board. It was a successful solution.

Old Man Emu