mains heated bed interference

hi,,

i have a prusa i2 which had a pcb heated bed uptill now which was running ok with only a problem of the bed not heating above 60 degrees because of the resistance of the bed being a bit high,,,

So i switched over to a mains powered 200w bed recently.. I connected the bed to the ramps board using a dpdt relay.. the bed works like a charm reaching 130 degrees c in 10 minutes ... but the problem now i am facing is that the switching of the relay is causing the motors to go bizarre. The motors randomly get enabled or diabled .. I have not yet tried printing with the issue since in the heating period itself the motors turn on randomly...

i am using a diode on the relay but still the problem persists...

any suggestions?

Hi..
200w are not enough...
if you have a multimeter and measure the 12 volts output, you will see that it drop to about 9 volts or less.
I have for that purpose a 600w power supply.

i mean the heated bed is 200 w and is running on 220 volts..... my rest of the printer runs on 360 w 12v led power supply

Sorry..
I did not understand ...
I'd like to help you but I do not see as I can.
try a shock filter between the ramps and the relay, maybe solve maybe not...

Edited 1 time(s). Last edit at 07/29/2013 05:46AM by novato.

Hi,

which firmware are you using? The bed should not be PID regulated. If you are using a relay, you must use the 'BangBang' style to drive the bed. Also use a schottky-diode as flyback for the relay and take care of the right polarity.

best regards

--- Lars ---

i am using marlin with bed in bang bang mode.... and also i have a diode across the relay.. this setup was working fine before for a 12v bed .. but the problem started when i switched to a 220v bed....

How about a Solid state relay?

---

_______________________________________
Waitaki 3D Printer

Can you make pictures of your setup? Especially where the electronics are and where the wires are placed ....

Change your relay to a solidstate relay and your problem will be gone. I am using them with mains powered heater pads on all my machines and not had one fail yet. Thermistor is built in and that is used as normal to control the electronics. The Mosfet that normally controls the 12 volt heat pad will switch the solidstate relay (no moving parts) and takes almost no power to operate. The solidstate relay then in turn switches the mains power to the heater pad.

@ regpye

that's what i was going to do next.....

thanks