Heated Bed controled with arduino relay modul and AUX Pin (D1)

Hello everyone,


As I'm new here, let me introduce myself. My name is Renaud and I'm building an FDM printer with a quite large building area using a cnc router. I should take some photos to show.
I don't have a lot of people around working with printer so reprap website and forum are very helpfull.
After a long period of development and fabrication I'm now trying to print. It's a work in progress as i would like to bring some improvement to it (from bowden to direct extruder). I'm now printing with PLA but the prints are warping and I don't like as I would like to make some functionnal pieces. I use marlin as a firmware with a ramps 1.4. For the slicing and g code generator i just bought Simplify 3D. It works great, i first used slicer and pronterface but had ome limits with the support building etc. I someone ant to have more information don't hesitate to contact me.
To avoid warping i would like to instal my heated bed. As the aréa is large, I don't use a standar pcb heater but rather a silicone heater made on dimension. It runs on 220v, (12v would require too high amperage) so I need to operate a relay to control the heating element. I have a standard arduino relay module working on 5v. As D8is 12v, I guess i cannot connect this relay to it. I would like to use one of the auxilary pins, but I don't know how to make the software modifications. I found out where to change from pin 8 to pin 1 in the pin.h file. for my particular setting but it doesn't look that simple. So my question is, what should I do to use D1 instead of D8 to run the relay with 5v (maybe the way marlin write the value to the pin is wrong ? Don't know)

hope you guys can help me with this issue.

Thanks a lot



PS: If ever I'm in the wrong part of the forum don't hesitate to redirect me.

Why not use a plain 12V relay or preferably an SSR instead of a relay module, and connect the relay coil to the RAMPS heated bed output? Then you won't need to modify the firmware. Don't forget to connect a flyback diode across the relay coil, if it is a mechanical relay.

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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].

Hello dc42, thanks for your answer. I don't use a SSR because I had the other at home and I think it's interesting to understand how things work. If ever it's impossible to use the arduino module I'll consider buying something else.

I just tried using a mechanical relay, and though it works, the Ramp board is obviously using microsteps and the relay because the relay is constantly turning on and off. Is there a way to prevent this?

If you are using a mechanical relay and it is switching rapidly you need to change the firmware not to use the PID control.

In your firmware find the section titled
"PID > Bed Temperature Control'
Look for the following command line and commit it out.

#define PIDTEMPBED

By placing // preceding the command

//define PIDTMEPBED

then recompile and upload.

Rapid switching of the mechanical relay can cause over heating and failure of the relay.
Failure of the relay could lead to some bad things like fire.

I do use a mechanical relay and like dc42 suggest I have the coil directly connected to the pin 8 of the RAMPS 1.4 board, it works very well.

I happen to find this on E-bay.

[www.ebay.com]

I have not used one yet, it cost more than the mechanical relay most folks use but you can use the "PID" switching with it.

The Power Expander from reprap.me is a similar design, basically a 5 terminal SSR.

Edited 1 time(s). Last edit at 12/15/2016 05:53PM by dc42.

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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].