I wouldn't think it switches very fast anyways. With all that metal, you should have enough thermal mass to make everything go very slowly. I bet you can also increase the hysteresis for the heater to only engage it once the temperature drops to 5 degrees under the setpoint.
I'll have to check this out once I get back Using a powerful heater would make printing small parts so much faster.
Seems awfully affordable... Just have to figure out the thermistor setup. Probably will mill a hole for it in the bottom of the aluminum and trench a small groove for the wires. Or order the heater custom made with a small hole in the center. Then I think I can just use an SSR on the Rambo to switch the 110v heater on and off in place of the original bed, right?
Good find Jim. I wonder if they make them in 24 vdc?
Post by jimustanguitar on Feb 18, 2014 1:32:35 GMT -5
I sent them a message and got a response in a day. Decent English.
I asked if their heaters went to 100C (wasn't sure what the target temp was for an oil pan heater) and they suggested 140 watts for a 280mm circle. I explained that I was more interested in 300-400 watts because I was heating an aluminum plate and because I would be controlling the temperature with my own sensors and switch, and they said to just tell them what I wanted when I placed the order.
Last Edit: Feb 18, 2014 1:33:08 GMT -5 by jimustanguitar
I think Felix is correct. After doing a quick little test, I heated the plate to 225f and shut it off. It has been over 30 minutes and it is still at 135f. It don't cool down very fast. So if I run my print first layer at 95c and all others at 80c I bet the plate never turns back on. (depending on how long the print takes). So I don't think I need to worry too much on over heating the realy.
Some things are meant to be closed. Your mind isn't one of them.
Post by jimustanguitar on Feb 18, 2014 13:39:00 GMT -5
John Oly told me last week that there's a place in the firmware to switch the bed heat from PID control to "on-off" control. I don't know what it's called in the firmware, but that's what John called it.
John Oly told me last week that there's a place in the firmware to switch the bed heat from PID control to "on-off" control. I don't know what it's called in the firmware, but that's what John called it.
/** Heat manager for heated bed: 0 = Bang Bang, fast update 1 = PID controlled 2 = Bang Bang, limited check every HEATED_BED_SET_INTERVAL. Use this with relais driven beds to save life */ #define HEATED_BED_HEAT_MANAGER 1 /** \brief The maximum value, I-gain can contribute to the output.
The Bang Bang setting could potentially be too fast, but not fort this bed.
Last Edit: Feb 18, 2014 13:46:37 GMT -5 by BeeAmaker
Some things are meant to be closed. Your mind isn't one of them.