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24V 300x300 MK2A Heatbed

Posted by Zuxztah 
24V 300x300 MK2A Heatbed
November 04, 2015 04:15PM
Hello! Sorry for my bad english!

I'm fairly new here in the 3D printing world and I just bought a Wanhao i3, but I was not really happy about the size so I build a 3D printer with a 300x300 MK2A Heatbed and dual (E3D V6 Extruders) I want to drive it at 24V?

Iv'e ordered a (BBP Fastbot) 3D Printer Controller Board
BBP1S
I calculated that it would draw somewhere about 15Amps at 24V (1.6 ~ Ohms)
each stepping motor (NEMA 17) rated for 1,7Amps each,
and I will use 6st step motors in total.
Stepper motor (42BYGHW609)

1x X axis GT2 Belt, and 20 teeth pulleys
1x Y axis GT2 Belt, and 20 teeth pulleys
2x Z axis 2x lead screws (8mm)
2x Bowden Extruders (E3D V6) (Mk8 Gear)
+
2x 24V 25W heater cartriges (E3D V6 Bowden)
2x 24V fans (extruder cooling Fans?)

will the (3D Printer Controller Board) Manage running (30 ~ A) or do I have to run a relay in parallel with the controller board?
Or is 30A even enough?


Sincerely

Edited 1 time(s). Last edit at 11/04/2015 04:18PM by Zuxztah.
Re: 24V 300x300 MK2A Heatbed
November 04, 2015 05:30PM
I found a switched power supply (Mean Well RSP-750-24 751.2 W) but the biggest question is.. Will the controller board handle it?
The power supply is rated at 31,3 Amps. @ 24V

Edited 1 time(s). Last edit at 11/05/2015 01:35AM by Zuxztah.
Re: 24V 300x300 MK2A Heatbed
November 05, 2015 03:29AM
Don't worry,
the stepper current of 1.7A is not the same current the driver is asking from the power supply.
I would try a 24V/19A PSU from Meanwell. Don't use a cloned one, I've seen they often miss some internal heatsinks.
-Olaf
Re: 24V 300x300 MK2A Heatbed
November 05, 2015 03:33AM
Okey smiling smiley are you sure that it's a clone?
[www.conrad.se]π=1293156

It's a Swedish "website" but the description is in English.

Will the controller board manage to supply the heatbed wit 15-20 amp? Without pcb burn? Or components burning up?

Edited 1 time(s). Last edit at 11/05/2015 03:35AM by Zuxztah.
Re: 24V 300x300 MK2A Heatbed
November 05, 2015 04:06AM
The fuse on the BBP1S board is 10A. If you are sure about the bed resistance of 1.6Ohm it won't be possible to use it directly.
-Olaf
Re: 24V 300x300 MK2A Heatbed
November 05, 2015 04:25AM
Is there any other way to heat the heatbed without using BBP board? Is it possibleI to use a relay? What kind of relay?
I Don't really know how the heatbed electronics works in detail?

assuming it's a power mosfet that triggers the heatbed on/off until it reaches the desired temp?
No pwm signal?

Or I might be lowering the voltage to 20V (lowest possible for the power supply I bought) but still there will be 12,5~ Amps? On the HBP port?
Re: 24V 300x300 MK2A Heatbed
November 05, 2015 04:36AM
Power supply >BBP> Heatbed power connector output > Relay (coil)
Powersupply + > relay pin 30 > relay pin 86 > Heatbed terminal +

Heatbed terminal - to Common grund on the power supply?

Would work if the HBP (HeatBedPlatform) output port puts out on/off signal?
Re: 24V 300x300 MK2A Heatbed
November 05, 2015 05:59AM
You could use a standard 24V relais, but a DC-DC "SolidStateRelais" would be better. Search the forum for dc-dc ssr relay for details and sources.
-Olaf
Re: 24V 300x300 MK2A Heatbed
November 05, 2015 07:45AM
Don't use a cheap DC-DC SSR. The cheap ones have too high a voltage drop so heating power is reduced (the SSR on the other hand gets very hot). The ones that are good enough cost about GBP65 or US$100.

This device [reprap.me] looks promising, but I don't have one, neither have I seen any reports on how well it works.



Large delta printer [miscsolutions.wordpress.com], Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: 24V 300x300 MK2A Heatbed
November 05, 2015 07:55AM
Hmm. Its not possible to use a overrated normal relay? Like 50-60 amps? Compared to the 25 amp draw?

Only the power supply Alone costs 167~ gbt then a ssr for another ~100gbt:/ wow...

I will buy one if I have to.
Re: 24V 300x300 MK2A Heatbed
November 05, 2015 08:00AM
The Power expander looks very interesting! smiling smiley but there isn't any specifications.
Or maybe I'm just blind xD
Re: 24V 300x300 MK2A Heatbed
November 05, 2015 08:26AM
You can use a normal relay if you can stand the constant clicking. The contacts may not last very long because of the amount of use. Be sure to connect a flyback diode across the relay coil.

The brief specification of the Power Expander is given on that page I linked to, however it didn't show up on my smartphone, only on my PC.

The draw of that bed heater should be about 15A, so in theory a SevenSwitch would just about handle it. However, the Power Expander looks a better bet because the ground wiring will be less critical, owing to the isolation it provides from the control input.

Personally, I use AC mains power to drive large heated beds, because that allows the use of a small power supply and a low-cost DC-AC SSR to switch the bed. However, use of AC mains power requires additional safety precautions to be taken, and I don't recommend it unless you are knowledgeable about AC mains wiring, protective grounding etc.



Large delta printer [miscsolutions.wordpress.com], Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: 24V 300x300 MK2A Heatbed
November 05, 2015 08:42AM
Okay I have some knowledge about ac power but didn't think about that erlier so I bought 3 cheap dc-dc ssr's anyway, better than nothing.

I will build a aluminum enclosure 5mm sheets for both power supply and controller board and mount the ssr to the inside wall with som thermal paste/glue and maybe add a 24V fan to cool it?

It's the heat from the ssr that's the problem? And maybe some power drop? Cause to slower heat up time? With the cheap ssr's?
Re: 24V 300x300 MK2A Heatbed
November 05, 2015 02:50PM
Quote
Zuxztah
It's the heat from the ssr that's the problem? And maybe some power drop? Cause to slower heat up time? With the cheap ssr's?

Yes. Cheap DC-DC SSRs drop between 1.5V and 2V. If your bed heater draws 15A @ 24V, than that's between 22.5W and 30W of heat generated by the SSR that you need to get rid of, and up to 15% loss of bed heating power.

Edited 1 time(s). Last edit at 11/05/2015 03:09PM by dc42.



Large delta printer [miscsolutions.wordpress.com], Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: 24V 300x300 MK2A Heatbed
November 05, 2015 03:44PM
Ok. Thats not good!
What happens if the ssr breaks?
Worst case scenario?
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