Duet- Hi-wattage heaters

Heya,

So basic functionality works okay.The 'factory' 24v PSU works @~23.7v idle... but is unknown to me other than that. For now its 12v ATX@450w

My thoughts were, using exsiting electronics to run the110V chamber heater, and the Duet to run a heated bed.

So using the Duet to power the bed it would wire up as instructed. I don't know if I want to switch to 24v everything... or not... so I don't have it yet.

To power the heater I was thinking I could wire it to an empty hotend pin(s) since I could set idle/standby extruder temp at prog. start, and turn it off at end and it would manage itself during. As power is being drawn from 'mains' so the function of the rest of the board wouldn't be affected.

When power is applied to the heater it does nothing... So I would assume I need to supply low power to the relay board to get it to do anything.
(DC42 has already mentioned He uses a SSR-10DA instead of... whatever I have... which I could slowly ramp up power until it works)

So then...

The thermometer(?) board. has 3 wires from the controller.
1- epoxy thermistor
1- MCP6H01E 'OP AMP'
1- orange block with "106 25k 338" written on it... I didn't find much in the way of electronics parts about it... lots of chairty running events though... -_-
there are also half a dozen resistors...

So I hadn't taken much notice of this thing until now. It would make sense to me if there was just a thermistor on it but i'm confused at the wording/use of the 'Op Amp' and what to do with 'the third wire'.

Just easier to bite the bullet and buy a 'room temperature' thermistor and an SSR or do you think this will work... or am I just wrong... ?

Thanks,

My guess is that the op amp is being used to do some signal conditioning. You would need to modify the Duet firmware to work with its output, once you have worked what that output is. So a simple thermistor with a resistance of between 10K and 100K @ 25C would be easier to use.

Relay boards invariable require power as well as a signal input. The other complication is that most relay boards take an active high input, but the heater outputs on the Duet are switched ground in common with most other printer electronics. An SSR will be easier to use because you can connect it directly to a heater output. Types SSR-10DA and SSR-25DA are widely available.

btw I intend to complete the support in the Duet firmware for a chamber heater and thermistor soon, because I want to use one myself. The GCodes for it have already been allocated.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I've printed several ABS parts and I underestimated the curl. In a cold room the curl is very dramatic. A 25mm disk will warp to failure before print ends. Where I previously have printed 216mm tall(wide-print) x 70mm wide (tall-print) x 6mm thick 'speaker stands' with less than 10mm of warp total in a heated chamber, cold HDPE(?) bed using unreliable adhesive. Unacceptable, but it was a somewhat predictable result....

So parts are ordered... I didn't care for many of the sellers I saw offering PCB heaters, nor the size, so I went with a silicon industrial heat bed @110v... even though there may be uneven heating(?) and two SSR for 400w chamber and 350w bed both @110v... waiting... waiting...

So... say I'm topping out @~4A(AC)+4A(AC)+2A(DC)*(9STEPPERS MAX@MAX) I'm still plenty clear for a 15-20A- AC circuit... yeah? I'm sure I'm missing a great deal but that's my best guess... and it wouldn't be my first electrical fire anyway...

Yeah... I don't have much to say in the 'safety' section...

You are right about the two heaters taking nearly 4A each, but the stepper motors will take much less current from the mains because they run at a low voltage and are fed through a switching power supply and then switching constant current regulators. It's something like this:

1 stepper motor at max current takes 1.5A at 3V, that's 4.5W at rest (check the specifications of your own motors). Allow a little more for when they are moving, say 8W average, times 4 is 32W. Add on the hot end heater, typically 40W, and something for the electronics, say 5W to be generous. That's 77W total @ 12V. If we assume the PSU is 85% efficient, that's 91W from the 110V mains - which is less than 1A. So your total maina current will be about 9A.

I use a 350W 230V bed heater and SSR in my delta. Details to be published on my blog soon.

Edited 1 time(s). Last edit at 05/23/2015 03:12AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].