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Multiple Heatbeds on one MOSFET?

Posted by mikeyy97 
Multiple Heatbeds on one MOSFET?
October 09, 2017 03:27PM
Hi Guys!

I'm new to this forum and I have an intresting question - one I couldn't find on this forum yet.
I've been into 3D-printing for two years now and I want to start building my own 3D-printer. This printer will have a large build area - aiming on 400x400x400mm with a heated bed. For the heated bed, I can go two ways:

1) I can buy a silicone heater pad from china on AC power coupled to the control board through a SSR. I don't prefer this method since all the time I need the heated bed, it will heat the entire build surface thus wasting energy when printing something that takes a long time...

2) With four traditional PCB heatbeds controlled individually there is no more need to waste energy, however the wiring is a little bit more complex. I'm thinking about using a 180A rated MOSFET module (https://www.123-3d.nl/123-3D-Externe-heatedbed-MOSFET-module-180A-i2327-t3117.html) and switches to turn on and off the heatbeds I actually need for my print. Running each individual MK2 PCB heatbed will draw approx. 5 amps (using 120W). 4 times 5 amps plus 10 amps spare means I need at least a 720W power supply. In the attachment you can see how the wiring looks like.

Now my question is:

- Is it possible to wire up four heatbeds onto that single 180A rated MOSFET providing I use one 720W power supply for the heated beds and another power supply for the control board/motors/stepper drivers etc?
- And if this works, is there someone on this forum who has experience with switching multiple heatbeds on one MOSFET/SSR?

I'd like to hear your thoughts!

open | download - 2psu.jpg (169.4 KB)
Re: Multiple Heatbeds on one MOSFET?
October 09, 2017 03:57PM
Your ideal is sound however your choice of parts I Believe is not.

I would choose a SSR and would choose a 40A, four beds at about ~5 amps each = 20 amps + 10 Spare is 30 amps
This would be a 24Volt supply at 30 amps = 720watts Supply

Single phase 24v dc dc solid state relay

Control Voltage 5-30VDC
Control Current 4-25mA
Reverse Voltage 30VDC
Guarantee close voltage 1.5VDC
Guarantee open voltage 3VDC
Load Voltage 12-250VDC
Load Max Current 40A
Load Mini Current 0.08A
Breakover Voltage ≤2VDC
Output Leakage Current ≤1mA
Medium withstand voltage ≥2500VAC
Insulating resistance ≥100MΩ
Switching time ≤5mS

Edited 1 time(s). Last edit at 10/09/2017 04:07PM by Roberts_Clif.
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