1 Topic by perlguy

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Topic: Is using an old (working) computer power supply a good idea?

Since I've had some issues with my Solidoodle power supply, I really don't trust it anymore.

I have a 400W computer power supply that can provide 17A at 12V.

I also have a Sparkfun "Benchtop Power" adapter so I can easily get the +12V from the computer power supply.

It seems to be more robust than the one that Solidoodle ships with, it just isn't as "pretty".

Is there any reason that doing this would be a bad idea?  I don't want to fry something else.

Thanks!

2 Reply by elmoret

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Re: Is using an old (working) computer power supply a good idea?

That's fine, but you have to load the 5v rail for it to work.

http://arduino.cc/forum/index.php?topic=113338.0

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3 Reply by jefferysanders

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Re: Is using an old (working) computer power supply a good idea?

Yep sure is, I use a 400watt ATX PC PSU.

4 Reply by Tomek

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Re: Is using an old (working) computer power supply a good idea?

It's a great solution, unfortunately on many PSU to get the full amperage on the 12V rail, you really have to load the 5V rail with at least an amp, not just a wimpy 500mA as most suggest. Here's my tip for loading the 5V rail:

Not only is it nice to have it loaded with a Alu resistor, but I also have a small incandescent bulb. Makes it easy to see if it's on, I can see it from across the room. (My PSU also has a small fan.) If you want, you can load it with a 5V fan cooling the Solidoodle electronics, and a small Incandescent bulb. That might even be enough that you don't need the resistor!

5 Reply by perlguy

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Re: Is using an old (working) computer power supply a good idea?

I've tried several PSU's hooked up to a SparkFun "Bench Top Power Board".

I can power and run my "FrankenDoodle" no problem, but I still have a question/concern...

I am not an EE, so bear with me.

With each thing that I turn on (extruder, heater), I get a voltage drop from the PSU.  My question is: should I be concerned about this?

Here is what I've recorded with 2 pretty beefy PSU's that I've tested with:

600W PSU With Load on 5V
Power on:  12.08V
Connect to printer:  12.08V
Turn on Extruder only: 12.00V
Turn on Heater only: 11.86V
Extruder & Heater on: 11.73V

600W PSU NO Load on 5V
Power on:  12.07V
Connect to printer:  12.07V
Turn on Extruder only: 11.99V
Turn on Heater only: 11.86V
Extruder & Heater on: 11.72V


1000W PSU With Load on 5V
Power on:  12.12V
Connect to printer:  12.12V
Turn on Extruder only: 12.01V
Turn on Heater only: 11.88V
Extruder & Heater on: 11.76V

1000W PSU NO Load on 5V
Power on:  12.12V
Connect to printer:  12.12V
Turn on Extruder only: 12.01V
Turn on Heater only: 11.88V
Extruder & Heater on: 11.76V


Should I be concerned about this?

I plan on powering one of those silicon heat mats also, and was wondering just how low the voltage drop can be before I should worry?

Also, is there any way to make the PSU maintain the voltage under a load?

Thanks!

6 Reply by perlguy

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Re: Is using an old (working) computer power supply a good idea?

I got my 200mm x 200mm silicon heating pad installed and have my computer PSU hooked up and running my Solidoodle printer...

When I have everything turned on, I can see a slight dimming and flickering of the LEDs each time the heater gets turned on/off.

Is this bad? 

Is there any way to make the voltage & amperage from the PSU be more stable?

Thanks!

7 Reply by perlguy

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Re: Is using an old (working) computer power supply a good idea?

OOps!

FYI

The stock SparkFun Benchtop Power board will NOT handle the load from the Solidoodle AND a 200mm x 200mm silicon heat mat!

Even if you put a bigger fuse on the SparkFun board.

(I just let the smoke out of my board).

Now I am praying that with the mods that Ian has done (related to getting power directly from the Sanguino board) that I don't smoke my motherboard too!

8 Reply by solijohn

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Re: Is using an old (working) computer power supply a good idea?

perlguy wrote:

OOps!

FYI

The stock SparkFun Benchtop Power board will NOT handle the load from the Solidoodle AND a 200mm x 200mm silicon heat mat!

Even if you put a bigger fuse on the SparkFun board.

(I just let the smoke out of my board).

Now I am praying that with the mods that Ian has done (related to getting power directly from the Sanguino board) that I don't smoke my motherboard too!

You could wire yourself up a relay to help control the flow of juice to the board. Our MOSFETs are pretty sturdy, so I don't see there being too big a danger of a fry out.

Of course electronics are quite unpredictable.

Former Solidoodle employee, no longer associated with the company.

9 Reply by perlguy

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Re: Is using an old (working) computer power supply a good idea?

Thanks, that is what I ended up doing.  I put a relay on it and use a separate 12V channel from my power supply.  It is working great right now!