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Question about heated bed
Posted by Koby_88
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Question about heated bed November 05, 2016 03:37PM |
Registered: 8 years ago Posts: 26 |
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Re: Question about heated bed November 05, 2016 03:45PM |
Registered: 12 years ago Posts: 2,470 |
Any 24v DC PSU that delivers the neccesary wattage + a bit (10-20%). There is nothing special to look out for.
[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]
[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]
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Re: Question about heated bed November 05, 2016 03:59PM |
Registered: 8 years ago Posts: 26 |
Yes but i dont know what is correct wattage for that bed 
I couldnt find specification. The bed i order is at link down if that can help.
[ru.aliexpress.com]
Edited 1 time(s). Last edit at 11/05/2016 03:59PM by Koby_88.
I couldnt find specification. The bed i order is at link down if that can help.[ru.aliexpress.com]
Edited 1 time(s). Last edit at 11/05/2016 03:59PM by Koby_88.
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Re: Question about heated bed November 05, 2016 05:48PM |
Registered: 10 years ago Posts: 14,672 |
My guess is that it will draw somewhere between 10A and 15A. When it arrives, measure its resistance with a multimeter, subtract the resistance reading when the multimeter leads are touching, and divide the result into 24 to get the current.
Most low end 3D printer electronics boards can't safely switch more than about 11A. On RAMPS electronics, additionally the bed heater polyfuse is only rated at 16V.
Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod
Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Most low end 3D printer electronics boards can't safely switch more than about 11A. On RAMPS electronics, additionally the bed heater polyfuse is only rated at 16V.
Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod
Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
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Re: Question about heated bed November 05, 2016 06:59PM |
Registered: 8 years ago Posts: 26 |
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Re: Question about heated bed November 06, 2016 01:51AM |
Registered: 10 years ago Posts: 14,672 |
I don't use RAMPS, but in theory you can feed 24V to the bed power input and 12V to the other one, and replace he 11A polyfuse by an auto fuse. However, the mosfet, connectors and PCB traces on cheap RAMPS boards may fry if you go much above 10A. The mosfet is easy to replace with a better one.
If you go the SSR route then you need to choose the SSR carefully. See [duet3d.com] for recommendations.
Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod
Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
If you go the SSR route then you need to choose the SSR carefully. See [duet3d.com] for recommendations.
Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod
Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
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Re: Question about heated bed November 08, 2016 09:59AM |
Registered: 11 years ago Posts: 471 |
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Re: Question about heated bed November 08, 2016 12:16PM |
Registered: 10 years ago Posts: 14,672 |
Quote
epicepee
You can probably run the heated bed through the RAMPS, but it's a lot of current. A nice alternative is to wire up a MOSFET to switch it on and off. It's cheaper and more reliable than an SSR, and takes up less space.
SSRs are very reliable unless you choose the wrong one - as a lot of people do unfortunately. An external mosfet (or even two or three in parallel) can work well, but only if you keep the ground resistance very low.
Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod
Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
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Re: Question about heated bed November 09, 2016 08:06PM |
Registered: 8 years ago Posts: 24 |
I use this MOSFET for logic level switching:
2N06L07
Pretty much ideal for switching high currents from 3.3v or 5v logic levels.
Driving a mosfet and keeping it in it's efficient range works best if you don't approach the max current and exceed the minimum gate voltage by a good amount.
I recently drove 3 of these in parallel on a prototype for a 12v 700W heated bed.
Gate drive current was < 4ma across the three of them at 400hz PWM.
They still got warm, but I was pushing ~20A through each one.
Edited 1 time(s). Last edit at 11/09/2016 08:18PM by darenschwenke.
2N06L07
- NPN Power Mosfet
- 2v ON gate voltage, 20v max
- 0.007 ohm on resistance
- 55v max drain-source voltage
- 80A max current
Pretty much ideal for switching high currents from 3.3v or 5v logic levels.
Driving a mosfet and keeping it in it's efficient range works best if you don't approach the max current and exceed the minimum gate voltage by a good amount.
I recently drove 3 of these in parallel on a prototype for a 12v 700W heated bed.
Gate drive current was < 4ma across the three of them at 400hz PWM.
They still got warm, but I was pushing ~20A through each one.
Edited 1 time(s). Last edit at 11/09/2016 08:18PM by darenschwenke.
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Re: Question about heated bed December 05, 2016 01:29AM |
Registered: 8 years ago Posts: 26 |
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Re: Question about heated bed December 05, 2016 02:14PM |
Registered: 8 years ago Posts: 24 |
I like the original xbox 360 PSU myself. Gives you 5v vsb (always on) at 1A and switchable 12v at ~14A.
They are cheap too. The slim version is cheaper, but gives 12A. Still enough without a heated bed.
They are cheap too. The slim version is cheaper, but gives 12A. Still enough without a heated bed.
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Re: Question about heated bed December 28, 2016 05:05AM |
Registered: 9 years ago Posts: 238 |
I have a 24V PSU with around 300-350W for the electronics (RAMPS, motors, hotend) and it seems to work fine. My heatbed through a relay feeds off another 24V PSU that's 400W, which is enough for a 400x400mm silicone heater.
Do make sure you test that relay while being ready to unplug it. The DC-current SSRs are rarer than AC counterparts, and I've come across a vendor in China that sent me a couple that nearly started a fire (they were rated for more than the current they were used for). Another vendor sent me good relays.
Do make sure you test that relay while being ready to unplug it. The DC-current SSRs are rarer than AC counterparts, and I've come across a vendor in China that sent me a couple that nearly started a fire (they were rated for more than the current they were used for). Another vendor sent me good relays.
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