programing your second hotend as a heatbed

hi
i have Aduino Mega 2560 R3 and ramps 1.4 .
i am using srinter + stineforge i would like to turn the second hotend into a second heatbed

i can not get my head round it so could any one help me (old age)

regards bill

im sure there is a good reason why you want to do this. I cant help with that, but I cant help but ask Why would you want to?

hi
i need for the machine in the picture

regards bill

The best way to accomplish this is going to be using a dedicated circuit for the heatbeds.

hi
ok your the master i am the student and humbled
bill

bill1957 Wrote:
-------------------------------------------------------
> hi
> i have Aduino Mega 2560 R3 and ramps 1.4 .
> i am using srinter + stineforge i would like to
> turn the second hotend into a second heatbed
>
> i can not get my head round it so could any one
> help me (old age)

If you run the heatbed at 12V on the second hotend it will overload the RAMPS, but you might be able to run two heatbeds in series at 24V throught the heatbed connector on the RAMPS.

If you need to run at 12V it's going to be a lot of current. An external relay or MOSFET would be needed as xclusive585 suggests. A relay is simple to use if you use with on/off (aka bang-bang) control, a MOSFET is generally better but slightly more complicated to build. You can get some off the shelf power boards if you don't mind spending a little more.

hi
so if i put a relay on the second hot end and do the same with the heatbead

still leaves the problem off programming the second hotend as a second heatbed
and getting it to work on stienforge

bill

Skeinforge is a non-issue, get the firmware to control both heatbeds as one.

I'd build a sevenswitch, connect it to any free, PWMable pin. One sevenswitch should be able to handle two beds if you are careful about mosFET selection. Or gang two sevenswitces on the same pin. Or patch the firmware so it PWMs two pins at once.

This has the advantage of leaving you with the original D8 mosFET, which will come in handy if you want to run dual extruders, normally you have to lose fan control to do that.

ok
i like the sevenswitch were to get and how to progam







bill

The way i would do it is. make a small pcb with 2 mosfets connected to an single aux pwm pin, supplied with 12v directly from the psu. then just change the pin in firmware for the bed.

hi
just one big problem ineed scimatic for it and the big big prob i have no i dear how to program this i tride

bill

awesome idea to make bigger prints.
If i were to do that and it was 12V i would just use a relay for the beds and use the normal bed output to switch it. No firmware programming and the relay should be @ an autoparts store.