using extruder 3 thermistor+heater connection for heated build platform
Location
I have some spare thermistors around (the right type for a RepMan hotend).
Now I plan to modify my existing heated build platform by clamping that thermistor onto the platform,
connecting it to the thermistor pin for the unused toolhead #3 and a relay onto the NiCr-wire pin
of toohead #3 that switches on and off the heating for the platform.
Maybe I also need an identifying resistor for toolhead #3 to identify it as an extruder.
That I would set the platform temperature in my g-code in start.gcode right after homing.
Do you guys see any problem with this aproach?
(Like the firmware adjusting for the added width of a 3-extruder y-carriage or something.)
So... no one has any idea if this can work and what problems this may cause?
Marcus,
I am currently purchasing supplies to build a heated bed. I would also like to control the temperature with extruder 3. Have you found anything out?
I know that the latest firmware (4.2.1)has a heated be version. Do you know if this version is for double or single head Rapmans?
The release notes state: "Added heated bed functionality for RapMan which allows extruder heater 3 to switch on simultaneously with extruder heater 1 or 2."
This leads me to believe that it is for a double head setup. Does simultaneously mean that the bed can heat up at the same time another head is heating? This is surprising to me as both heads can't be heated at the same time normally, but I suppose since it is just powering a relay, it might not be an issue. Do I need to make a special circuit to prevent overloading of the PSU?
Do you know what resistor I would need to connect to pin 22 so that the firmware knows it is a heated bed? Are the resistors for EX1 and EXT2 both 300 ohm resistors?
Also as Bogdan stated here
"Wrt this heating issue, I mentioned long time ago that I'm heating my hot end via relay because it is too slow to heat it via pcb, maybe a M-code to allow all three extruder channels to be heated at the same time for us who have the hw that can actually do that."
Can this be implemented? It would be awesome.
Any help would be great,
Jason
Is Bogdan's relay still working on the 3.3 board?
= is the 3.3 board still just switching +12V on and off for the heater or does it have an analog 0-12V output and I need a different relay now?
( http://wiki.bitsfrombytes.com/index.php?title=User:Bogdan.kecman#Electro... is from the old 3.0 board)