Can I use relay to control extruder heater?

Hi everybody, I have a relay which I can control via arduino. I wanna use this relay to control extruder temperature. Is it possible on teacup firmware? I just saw pwm pin options there.

Please let me know.

Thanks!

Edited 1 time(s). Last edit at 07/03/2013 11:33PM by meybivi.

you dont have to change anything in firmware....just put relay trigger on pins where you connect hot end heater.
so when firmware turns heater on it will trigg relay and that is it.


just make shure that that you dont have problems with relay, it would not be nice if relay stucks on powered state...

so you need relay that triggers on 12V

Edited 1 time(s). Last edit at 07/04/2013 12:28AM by woo.

Thanks! I did it and it works except of when extruder reaches to target temperature the relay clicking over and over. Can I add some delay there like + -10 degrees?

not sur but i think there is already a temperature interval depending on the firmware you use...

+/- 10° on the nozzle will give you a load of problems on extrusion. Why don't you use MOS FETs instead? They are used in RAMPS etc. for a reason.

I am running my heatbed through relay, haven't seen a hotend through relay yet, but I guess it would work the same way Good luck!

Thanks for answers. Seems like I better to not use relay for hot end.

Ohmarinus Wrote:
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> I am running my heatbed through relay, haven't
> seen a hotend through relay yet, but I guess it
> would work the same way Good luck!


You can get away with using a relay on the heatbed because of the lower PWM frequency. The extruder's PWM is much faster and will destroy that relay quickly. MOSFETs with a low RDS-ON is the way to go in both cases.

Mechanical relays can't do PWM at all. Even 15 Hz, which is the slowest you can get, and only with some ATmegas, is way too fast.

You can use simple bang-bang: turn the heater on if the temperature is too low, turn it off if it's to warm. That's what many firmwares use for the heated bed (high thermal mass, relative low heating power), but for extruders, this would likely wear out the relay within a few days, too.

There are MOSFET based DC relays, like the (shameless plug) SevenSwitch.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

You can use a solid-state relay for both the hot-end and also the heated bed.
I am using a DC-DC solid-state relay for the hot-end as I am using 12 volts DC, but the heated bed I use a DC-AC solid-state relay because it is a mains powered heater pad. Being as they are solid-state an have no moving parts, the switching on and off (very fast) has no problem or sound.
Both work fine, no issues at all. Overcame my power problems and the over heating at the Molex plugs on the board as the solid-state relay uses very little power to switch on and off (almost none)

Cheers,
Reg