Heated bed (AC) on Ramps, support needed.

Hi guys, just got my old Mendel Rep(St)Rap printing at last (I've been,unsuccessfully hacking away at an old set of gen3 electronics and finally upgraded to ramps). Though there is some slight calibration to be done my main concern is my heated bed. Printing ABS, it didn't take long for me to run in to some serious warping. I've got an old print bed with separate AC power, controlled by a CX380D5-relay (http://reprap.org/wiki/Heated_WolfBed) from GRRF.de, originally intended for my old gen3...

Now to my question: how would I go about making the bed run of my Ramps, preferrably without having to hook up the second, 11A, power supply? Since the bed is powered on it's own and only needs a control of 4-15V I figured it could run on way less than 11A, I don't really wanna bring in a bulky PSU-hack in the equation... Can D8 be run on much lower current without the 11A connected? Is it possible to hook it to some other connector and point to that in firmware?

Any ideas/suggestions?

(Ramps 1.4, Sprinter firmware)

Cheers!

Should be straight forward.

1.) Hook up the + from the RAMPS output (D8 +) to the + of the relay (Pin 3)
2.) Hook up the - from the RAMPS output (D8 -) to the - of the relay (Pin 4)
3.) Hook up one of the AC wires directly to one of the heating element terminals
4.) Hook up the other AC wire to an in-line fuse, then to the relay (Pin 1)
5.) Hook up the relays' Pin 2 to the other eating element terminal

Done.

It would be a good idea to have a bi-metal fixed temp thermostat attached as well to prevent a runaway condition. A thermal fuse is a good idea as well. Just wire either device in-line with the AC leads.

As far as the 12VDC source, simply shunt the positive RAMPS terminals (5A and 11A) together and hook up you positive 12VDC to either one. No need to do anything to the grounds, they already common at least according to the schematic.

Don't worry about the current draw of the SSR, it's nearly nothing (15mA DC). [www.crydom.com]

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

Cool, figured it couldn't be drawing that much... The wiring should be good to go, thermocouple is giving good readings (only ambient temperature so far though). I'll go ahead and connect the 11A terminal to my 5A source as well and give it a go tomorrow, see if we can't lose some warp...

Thanks for the help mate!