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controlling 4 heat beds using SSR

Posted by Dhinesh ks 
controlling 4 heat beds using SSR
June 16, 2018 01:22AM
Hi guys...
I would like to increase the work space of my printer. So that I planned to use standard 200x200 heat beds of (four no's). here the problem starts, I am in confusion that how to provide connections for those 4 heat beds using single RAMPS 1.4.

Since RAMPS is having single provision for controlling single heat bed. I so how can I connect 4 heat beds to a single RAMPS and I don't know how to control the temperature using that. So far I have read all the discussion topics related to this multiple heat beds. people are saying make use of SSR.

Eventhough I am not clarified, How to provide connections for Four heat beds using SSR and RAMPS1.4?..

Need a help from you guys!!!
Re: controlling 4 heat beds using SSR
June 16, 2018 02:34AM
No provision for this in ramps hardware or firmware

and bluntly it is a really silly idea. A larger mains powered bed if far safer.

If I was forced at gun point to do this...
you need
if 12v beds thats 44 amps, going to need at least 2 dedicated 25amp power supplies.
if 24v beds thats a little better only needing 22amps.
Nb you make any electrical errors with this and you are dead.

a number of these [www.ebay.com]
As this can be directly controlled from a 5v io line. So they are easy to attach (other external mosfets need 12 to control them, meant to be controlled by existing mosfet)

then you need to add more thermistor support to the ramps either 2 or 3 depending if your already using 2 or 3 on board thirmistors, this is easy, you just need a few analog IO lines resistors and caps...

and finally you need to rewrite the firmware to handle this..

This is a huge job, vs just buying a bigger heater.
Re: controlling 4 heat beds using SSR
June 16, 2018 07:37AM
What are the heater specs?

If they are line powered and you aren't trying to control them independently, just connect them in parallel and use a single SSR to switch power. You'll need a single thermistor, probably best placed at the center of the bed, to monitor temperature.

Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: controlling 4 heat beds using SSR
June 16, 2018 08:03AM
Standard Mk2 heat bed (200x200)...

Is single PSU is sufficient or both heat bed and control board or do I need to provide separate PSU's.
Re: controlling 4 heat beds using SSR
June 16, 2018 12:51PM
Unfortunately, those bed heaters are generally underpowered unless you're satisfied printing PLA. If you want to print ABS you'll be waiting all day for them to get the bed up to print temperature, if they ever do get there. The problem with 12V heaters is that they require a LOT of current which means you need a big power supply and heavy gauge wiring, and a heavy duty switching device to handle the current.

A heater doesn't care if you give it AC or DC, so there's it's a little silly to use a regulated power supply to drive a heater. For large beds, line power is the best option for heating.

As a point of reference, I have a 750W heater on a 300x300x8mm bed plate and it gets to 100C in about 4.5 minutes. The circuit is very simple, and it uses an SSR without a heatsink to switch all that power. Using a line powered heater means you can use a smaller, cheaper, quieter power supply for the rest of the printer.

This site has a calculator that will give you some estimate of the time required to get up to a target temperature based on the materials and the heater power applied.

Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
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