Heat bed + Bench PSU

[r007]

Hello,

I have been reading a lot in this forum about people buying a separate 24v PSU to power the heat bed. After looking into it it looks like the PSU and the SSR can get pretty pricey. So i was doing some test circuits for school yesterday and i was using my 0 - 30 V bench power supply and i thought why not try hooking up my Bench power supply to the heat bed.

Can anyone see why hooking up a bench power supply set at 24V directly to the heat bed would be any different then buy a 24 V power supply and a SSR??? it is essentially the same thing, no??

[img]http://static1.squarespace.com/static/5 ... ormat=750w[/img]

Regards,
Ryker

[r007]

Oops i just found the heat bed how to section.... could someone move this thread over there maybe??

[IMBoring25]

Are you planning on managing the temperature manually? The SSR gets the bed power off the board but still under the board's control to maintain set temperature. Full-time 24V power to a stock Onyx would likely get things hot enough for something bad to happen.

[r007]

ahh right. I wonder if I could just use the bench power supply as a replacement to the 24 V PSU in a similar setup with the board and SSR.

[Windshadow]

i think a bench PS like that will be a lot more expensive than one of the 24 volt supplies that are being sold buy companies like meanwell
perhaps twice as much but if you already have one then sure go ahed and use it with your solid state relay

[Jimustanguitar]

It all depends on what current the PSU is capable of.

[Eric]

Nothing wrong with a bench supply if it can do the job. Sadly, the bench supply in your picture can't do the job, since it's only rated for 5 amps. Not even close to what you need for the heat bed.

But you could use it to illustrate to yourself how the current requirements go up with voltage. Hook your supply up to your heat bed. Start at 0 volts and start increasing the voltage while watching the current display. You'll be able to get to 5 amps or a bit more before the power supply cuts out on you.

[IMBoring25]

Some quick googling suggests that particular unit has two 5A outputs. Even run in parallel that wouldn't cut it.

[Eric]

Some quick googling suggests that particular unit has two 5A outputs. Even run in parallel that wouldn't cut it.

His picture is of a single-output unit. You probably found the 305D-II, which is essentially two independant 305D's in a double-wide box with a couple switches for series or parallal operation.

[r007]

Well. Looks like I will be saving up for a 24v power supply. Thanks for all the input from everyone. It is much appreciated .

-Ryker

[3D-Print]

I just upgraded to 24V and so far (limited use) it has been awesome. My bed heats to 100 degrees quicker than the HotEnd gets to 220 degrees!!!

I used the Mouser (http://www.mouser.com/ProductDetail/Mea ... 5rFg%3d%3d) 24V, 31.3A power supply stock # 709-RSP750-24. I then used a step down (24V to 12V) transformer http://www.amazon.com/gp/product/B00BWK ... ge_o04_s00) to power the Duet and other 12V dependent items (i.e. DueX and my chamber temp probe). I then used the solid state relay (SSR) that was detailed by mhackney (http://www.auberins.com/index.php?main_ ... cts_id=288) which is activated by the Duet to power the Onyx with 24V. Here is a rough drawing that details how I wired the system, minus the 24V to 12V step down transformer.

[r007]

That is awesome. that drawing makes it really easy for me. If its working well for you maybe i will give a similar setup a try. Thank you very much.

[3D-Print]

That is awesome. that drawing makes it really easy for me. If its working well for you maybe i will give a similar setup a try. Thank you very much.

If you watch for PS's on ebay or other, they often pop up and are cheaper. I was impatient and bought it new which is a bit pricy! EagleSoar posted some similar listings (was less amps) the other day.

Here is how I upgraded (http://forum.seemecnc.com/viewtopic.php ... 125#p86387) which is really a compilation of this communities comments/insights!!!

[addisonElliott]

Actually, I just got done doing this upgrade myself. I found a fairly cheap method of doing this and I would like to share it with you. The bed is ~1.2ohm and the voltage is 24V, so this will give a power of 480W. Power supplies are typically not this efficient so you want to look for something in the range of at least 600W in my opinion. In my case, I used two 12V 500W (This is alright because each power supply is 240W) and connected them in series. Afterwards, I used battery connector cables to connect them to the bed and a SSR to relay it.

Here is what I bought:
Battery Connectors
12AWG wire to connect
SSR 100A
Lot of 2 Dell PSU

Together this turns out to be around $50. This is just a general idea of what I did. You would need to find out how to solder battery connectors and modify the PSUs so that one of them has a floating ground.

[Jimustanguitar]

A 1.1. ohm heated bed will draw almost 22 amps @ 24vdc. And that's when it's cold, it probably draws more when it gets hot.

[addisonElliott]

Yeah, that is true, but the power supplies are 500W. So that means, in theory, that each one could supply 500W / 12V = 42A. That's about double what is needed.

[Eric]

Yeah, that is true, but the power supplies are 500W. So that means, in theory, that each one could supply 500W / 12V = 42A. That's about double what is needed.

As a rule don't do wattage math to select a power supply. The numbers you should use are the current ratings actually listed on the power supply label. In this case, it's almost the same (DPS-500CB label says 12V at 41A and 5V at 2A), but on other supplies you could really fool yourself.

But yes, two 12V 41A supplies correctly connected in series will give you a 24V 41A supply. There are serious safety issues if you don't do it correctly, so really understand what you're doing or find a really good writeup.