Ormerod from RS

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Hi there,

We got our Ormerod just this week, last night as we were attempting to assemble it, we hit a problem, it didn't come with any of the required wiring looms, as the instructions said it would. Is this a common problem, is it a radionics problem, or reprap???


thanks,
Ryan.

Hi Ryan,

One of the bags of parts was missing in my kit too. I emailed RepRapPro about it and they sent me the missing bag straight away.

Edited 1 time(s). Last edit at 03/29/2014 03:45PM 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].

Hi RyanVeitch

Sorry for the missing parts. All the kits are packed by hand, and it's quite a complicated kit, so we do make mistakes occasionally. RS don't stock any spare parts, you need to get them from us. We don't have access to the RS customer database, so please email us on support at reprappro dot com with a description of the problem, your full name and address, your RS order number, and whether you have a kit with red or green plastic parts, and we'll send out the parts you need as soon as we can.

Ian
RepRapPro tech support

Hi Ian

Just a quick question as I'm struggling to get my thermistor in my hotend working (it keeps displaying -273).

I've connected it up correctly (as far as I can tell) and when I disconnect it from the control board and check the resistance of the thermistor circuit with my multimeter it returns a resistance of about 125-130 K-ohms, which seemed about right.

I then figured to test the control board I could set resistance to 0 and see if I got the highest reading I could. I then shorted out the two hot end thermistor pins and pronterface was still returning -273.

From what I've tested I'm thinking that the problem must be originating within the board or the software.

Any suggestions?

Sorry if this is abit all over the place, I'm at a complete loss.

Tom

Hi Tom

This is the easiest way to test the Duet is responding correctly; with the hot end heater off, disconnect the thermistor wires, and put a known-value resistor in place. The following resistor values should yield the following temperatures (if you get a temperature fault, because it is disconnected for more than 1 second, reset it with 'M562 P1') :
100k ohm = 25C
47k ohm = 42C
10k ohm = 84C
1k ohm = 173C
470 ohm = 212C
220 ohm = 261C
100 ohm = 321C

This will help diagnose if the fault is with the Duet, or with the thermistor wiring.

If the board is always reading -273, it's probably a board fault. Please email me on support at reprappro dot com with a description of the problem, your full name and address, your RS order number, and whether you have a kit with red or green plastic parts.

Ian
RepRapPro tech support

Hi Ian

Sorry aboutthe long wait. I was under the impression that I would receive an email when you replied but I didn't and only just today came on to see if anything way here, turns out there had been for quite a while.

I went out and bought a 100k ohm resister which i placed in the circuit instead of the thermister. The circuit then was working (giving a reading of -2.4deg). Then I checked the resistance over the thermister, while it was completely disconnected from the circuit and it read 100k ohm

This lead me to think that it must have been a connection of the wires to te thermister so I resoldered the thermister into the circuit and it worked for 2 tries of the reseting and testing (M562 P1 followed by M105) procedure, but then it stopped working again.

Then I looked at the connections elsewhere and found that the female port going into the ciruit board was quite loose so i jiggled it abit and the thermister started working again.

I then unplugged the circuit from teh board and just placed the resister on the pegs and the readings were correct.

All this is leading me to believe that I may need a new lead going from the board to the suspended section (lead going from board to hot end fan, probe and thermister) Is it possible to buy just this lead and if so how much is it?


TLDR; can i buy a new lead from the board to the thermister?

Tom

PS I've now clicked the follow topic box

Tom, are you sure the problem isn't in the 6-pin hot end connector? I had similar issues and that's where the problem was. You need to make sure that the pins are pushed fully home into the plastic shell, otherwise they may not make contact.

If you do need a new cable then I am sure RRP will supply one free of charge.

Edited 2 time(s). Last edit at 05/02/2014 04:31AM 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].

Tom, can you email me, on support at reprappro dot com ? Particularly if you are going to need parts, it needs to go through our system. The forum and private messaging on the forum isn't an 'official' support channel.

Regarding the readings you got; if the 100k resistor reads -2.4C when directly connected to the Duet, it generally means that the Duet needs to be replaced, which we'll do under warranty. The temperature sensing is affected by the Analogue to Digital Converter (ADC) in the Duet, which are quite variable at the limits of their capability. We regard a temperature of between 16C and 30C acceptable when a 100k resistor is plugged in; any lower than 16C, and the board will register -273C at ambient room temperatures of 10 to 15C. The temperature accuracy improves drastically as the temperature increases.

Poor connections will also cause higher resistance, so check your wiring first, and the connections in the hot end connector, as dc42 suggests. We'll replace anything that was supplied damaged under warranty, but this does need to be done by emailing us directly.

Ian
RepRapPro tech support

Quote
droftarts
Regarding the readings you got; if the 100k resistor reads -2.4C when directly connected to the Duet, it generally means that the Duet needs to be replaced, which we'll do under warranty.

Great that you're offering him a warranty replacement board! In another thread I pointed out an alternative solution to another user having the same problem (AFAR he lives overseas and didn't want to wait for a new board):

1. Connect a fixed resistor in parallel with the thermistor to bring the readings closer to room temperature, Somewhere between 100K and 220K should do the trick.

2. Pretend that the added resistor is in parallel with the 1K series resistor, and work out the resistance of the parallel combination. This gives the effective series resistance.

3. Set that as the series resistance using the R parameter in the M305 command. Use the H parameter to trim out any remaining temperature offset.

Obviously this solution is most appropriate for those who are used to soldering and have or can easily get a selection of resistors.

Edited 1 time(s). Last edit at 05/02/2014 05:15AM 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].

Yes, we're replacing the boards with ADC readings that are out of range. They'll come back to us, and then back to the manufacturer, the idea being that they will rework them with higher value sense resistors, I think. As Adrian pointed out to me, you pay a lot for accurate ADCs, particularly fine measuring ones! These are manufactured and tested to exacting standards. So the variability in the ADCs of the cheap Due ARM processor is to be expected, and is most likely caused by minute variations in track width within the processor changing the resistance. Our next batch of Duets will have higher value sense resistors to negate the problem.

It's still a small proportion that are far out of range. We test any that go out as warranty replacements, though. The boards are tested by the manufacturer, but I'm still not convinced how rigorous they are.

Ian
RepRapPro tech support

The surprising thing is that the SAM3X ADC is so much worse in this respect than the ADC in the Atmega processors used in earlier RepRaps, despite being 12-bit vs.10-bit.

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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].

Hi all

I've just turned my ormerord on at the power source and the hot end fan didn't turn on. I've had it working before but now it seems to have stopped but I don't remember changing anything. has anyone else had a similar problem?

From previous posts, I believe there are two common causes of this:

1. ATX PSU has failed. Is the fan on the ATX PSU turning?

2. Bad connection to the wire that carries 12V from the ATX board to the Duet, because one of the screw terminals has come loose. These terminals need to be re-tightened regularly, especially if you tinned the wires instead of crimping the ferrules on.

Edited 2 time(s). Last edit at 05/20/2014 06:19AM 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].

cheers dc42.

the ATC fan was working so i undid the 12V wires and re crimped and soldered them. fan working again!

Dc42, not sure that the ADC is worse - rather that the sense resistors we used to be a better fit at 160C + make it a worse fit at 16C.

Quote
T3P3
Dc42, not sure that the ADC is worse - rather that the sense resistors we used to be a better fit at 160C + make it a worse fit at 16C.

TPT3, the ADC in the SAM3X is worse, at least in the typical case.

For the atmega range, the datasheets quote the gain and offset errors as typically 2 LSB. For the SAM3X8E, the gain error min/typ/max are -64, -23 and +12LSB. The offset error min/typ/max are -30, +11.5 and +56LSB. So allowing for the fact that the SAM3X8E ADC is 12-bit and the atmega ADC is 10-bit, the typical gain error of the SAM is 3 times worse than the atmega and the typical offset error is 1.5 times worse. The worst-case errors of the SM3X8E are appalling.

You would probably have got away with using 1K resistors with the atmega processors.

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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].

Dc42, Ahh you are right - never compared the datasheets before.

DC42 - calling the SAM3 ADC characteritics appaling is a bit harsh!

I believe the SAM3 outperforms the atmega series an order of magnitude in terms of sheer sampling speed , which was a major design goal I believe(See link below). Adjustable gain, differential inputs 1 usec per sample versus 65 usec for the atmega I think (200 kHz max clock * 13 ck cycles per sample AFAICS).

Some useful info on SAM3 calibration here

regards
Andy

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Ormerod #318
www.zoomworks.org - Free and Open Source Stuff

Yes, the SAM3X sampling speed is indeed much better than for the atmega. Although that's irrelevant in the Duet, because nothing needs to be sampled that fast. It's the gain and offset errors that I said were appalling. I guess it's because the SAM3X has an amplifying buffer on the ADC input. It's a pity that you can't bypass the buffer when you are using it single-ended with a gain of 1, as the Duet does.

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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].

Its true that its not as convenient as the simpler A2D , however the gain and offsets can be largely eliminated by calibration. With that done , you effectively get much better accuracy by being able to take the average of more samples.

The pdf note in link above suggests to use 0.1 %resistors to set the calibration points at 20% and 80% of the supply, but I am wondering whether it may not be possible to use the hot end board PWM to set the calibration points which anyway is trying to simulate a DAC ( if I understand how it works correctly)

As always apolgies for talking about it rather than doing it!

regards
Andy

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Ormerod #318
www.zoomworks.org - Free and Open Source Stuff

I guess you could make up a small board that plugs into the expansion connector, containing 3 resistors to provide 2 different voltages to feed to 2 spare analog inputs of the SAM3X. The gain and offset errors should be the same for all inputs as there is only one amplifier. But it's a shame that this ADC needs calibration. I have never needed to calibrate the ADCs on atmega and attiny processors, because the gain and offset errors in these processors are very small (at least if you don't use the amplifier that some of these processors have).

RRP's solution is to increase the value of the series resistor, so that less ADC accuracy is needed at the bottom of the temperature range.

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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].