Hotend Fan and Bed Thermistor Error

Hi,
A couple of graduate students and I have assembled an Ormerod and we are keen to start printing. As always there are small stumbling blocks.
1. We've followed all the given instructions for assembly and commisioning at RepRapPro and of course scoured the forums here for further info.
1.1 Our first issue: Arduino 1.5.6 R2 installed (we've since rolled back to 1.5.5 R2). In Serial Monitor we get
"RepRapFirmware is up and running"
"Temperature measurement fault on heater 0, T = -273.1

As a note, we are using Windows 7, the Firmware as indicated is the latest installed (0.57a 2014-01-16 Green kit from RS). Does the thermistor on the board really control that much? Is there a way of running the printer without a heated bed?

1.2 Switching on the ATX, the fan of the hotend does not start spinning. Naturally if we pull the cable leading to the hotend then the reported temp on Heater 1 goes to -273.1. If not it usually hovers about 8.4 in both Proterface as well as in the Serial Monitor.

Is this simply a non-connection issue? Is there a way of checking if the motors work while we sort out the hotend and bed?
If the hotend fan isnt spinning is this the cause of everything? Will this feedback to the board?

Please advise,
Thanks

Yes it's probably a non-connection issue. If the bed thermistor is not connected, it will read -273. It is very difficult to get good connections to the bed thermistor wires by crimping because they are so fine, so I recommend soldering them. Then check that the pins are pushed far enough into the 2-way housing so as to get a good connection when the connector is mated.

Likewise, the reason for the fan not working is probably either a bad connection in the 6-way hot end connector, or you have the wires connected to the wrong pins on the Duet board.

Failure of the fan to spin won't stop anything else working, but failure to get a sensible bed temp reading will.

PS - once the bed temp had read -273 for a few seconds, it will stick there even if the fault is corrected. You can reset it either by pressing the reset button, or by sending M561 P0.

Edited 2 time(s). Last edit at 03/27/2014 12:04PM 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].

Thanks. We'll have a look and give it a go.

It's alive! Thanks for the advice.

We soldered the bed thermistor wires together, also crimped the fan wires better, flipped around the ribbon cables on the bed and rechecked the fan and hot end wiring. The power supply wiring needed some reseating and everything was good to go. Need to complete the axis compensation before further test printing. We did notice that the x-axis arm is "drooping" slightly.

Further to this we used one of the glass plate bulldog clips to keep the y-axis belt slipping.

Everything seems set. Will keep posting.

To prevent the y-belt from slipping I recommend Matt's y-belt clamps here [github.com]. To adjust the y-belt tension, also print my spacers here [github.com] and slip them under the y-belt clamps as needed.

Also, I strongly recommend using 3 adjustable bed-levelling screws, as described in the instructions for manual bed levelling, except that the front outer 2 screws need only clamp the heat spreader to the heater PCB and not go right down to the bed support. If you do a lot of printing, then consider replacing or reinforcing the bed support. For holding the glass in place, instead of using the foldback clips, use picture frame clips as described here [forums.reprap.org] and 2 posts after that.

Edited 1 time(s). Last edit at 03/29/2014 09:38AM 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].

Thanks. Keen to start printing.