Aux power out - suicide?

[am001 0]

I am running a water cooled head on my UM, and I want to find a way of cutting the power to the pump once the print has stopped, for example if I run overnight.

Ideally I need a pin that can switch a MOSFET on the 12V line as an aux-out for the pump. It needs about 500mA so its more than could run from the existing fan outputs.

I know Daid did a suicide implementation a while ago which could do it by shutting the whole machine down, but I can't find this now, and I don't think it made it into the main Marlin build.

Any thoughts?

Thanks.

Andrew

 

[Daid 303]

I wouldn't draw from the 12V line of the UM electronics, there is a bit too much load on it already. You could use the Heater2 output.

 

[am001 0]

Hi,

Yes I have a 2A switching regulator in place of the 7812, so no problem there.

Is there an easy way of making the heater2 output active only when printing?

 

[jonnybischof 60]

The heater2 output is coupled to the heater2 temperature sensor.

If you set the heater2 to 100°C target temperature, but the temperature reading never reaches 100°C, then the output will always be switched on

Of course you need a firmware that enables the heater2 output. And you need to solder in some fixed resistors on the heater2 temperature input so that it will always read the same temperature.

-> When the print is done, target temperature will be set to 0°C so the heater will switch off. Make sure heater2 temperature doesn't read below zero degrees

 

[am001 0]

Thanks Jonny, thats kind of what I was thinking. The only drawback is it stops me doing a dual extruder in the future, but I'll give it a go.

 

[Daid 303]

You can also use the M42 command to control the 2nd/3th heater output if there is only a single-extruder extruder and no heated bed configured.

 

[am001 0]

Sounds good, but I do have a heated bed... I'll look up M42 though.