You have failed me for the last time opsen sorce communtiy!!!

OK, not really you, my beloved horde of hackers . But there is something of value that I'm trying to salvage in the whole Makerbot-going-closed-source fiasco. Not just the Makerboters, but the UP!sters, the Ultimakers, and the 7 people who buy my stuff on Ebay, demand a solution to this dilemma. Sailfish firmware and the Mightyboard are a grave threat to our little niche. Whom of you really understands how it works? I'm a genius and it beat me. Short of buying a Mightyboard and reverse-engineering it from resistor to capacitor, I'm at a loss. Rise my minions. Bring me a solution to this monstrosity. http://www.thingiverse.com/thing:121966

I think you are beat.

It's designed it so that the MAX6675's (that drive the thermocouples) communicate via SPI, so you can't just connect the thermistor to those ports and hack the circuit.

Bonus points in that there are also no analog input pins available to connect the thermistors to. And then there is the support circuitry you'd need to drive the thermistors.

Does Sailfish even support thermistors?

Perhaps a daughter board to read a thermistor and spoof a thermocouple output to the Mightyboard?

But honestly, the solution may be worse than just biting the bullet and buying the thermocouple.

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

I think the board supports a thermistor for a heated build platform, but I haven't figured out how to upload new firmware to change pin assignments. Even If I knew how to do it, I wouldn't be able to confirm it worked since I don't actually have a mightyboard.

Heh, your fault for supporting dead end closed source product.

Ditch Makerbot and use open source solution if you want help.

Face palm, the mk7 and the mightyboard are open source.

Maybe ask in the electronics subforum?

---

- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

ohioplastics Wrote:
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> Face palm, the mk7 and the mightyboard are open
> source.


Great, so go ahead and change it then.

I'm crowd sourcing this one. You get a shiny new hot end if you figure it out. ebay.com

If you don't mind some soldering and coding, you could make a thermistor-to-SPI converter with a MAX6682. The format and degrees/LSb is different so the firmware will need changing to cook the data differently, and you'll have to choose the right value for Rext to program the thermistor scaling. It's also SMT so there's that. At least Maxim gives free samples, and it shouldn't require more than a couple extra components.

I need an easy to use guide, like a tutorial for my customers on how to modify there boards.

You can download the schematics for the mightyboard from thingiverse.

Look at the section on the schematic labelled "thermocouple". (attached)

Thermistors and thermocouples are completely different devices (thermistor changes its resistance, thermocouple changes its voltage), they are not at all compatible. As suggested above, you would need to make a thermistor to digital converter, replacing the thermocouple electronics.

As an alternative you could also make the thermistor to digital converter using an attiny (for example attiny2313), which would be cheaper than the MAX chip.

But why not just use a thermocouple?

Edited 2 time(s). Last edit at 07/23/2013 04:58PM by lajos.

Because it already supports a thermistor for the HBP and it's got tons of auxiliary pins. It shouldn't be that hard to edit the firmware and come up with a wiring solution.

Looks pretty easy, just wire thermistor and suitable resistor to PK6, then simple matter of changing the software.

If you use the heatbed thermistor input for the extruder, how will you control the heatbed?

But the bigger issue is that sailfish doesn't support thermistors for the hotend. It's not a question of reconfiguring the pins, it's forking sailfish and rewriting the ExtruderBoard class.

You will also need to modify the voltage divider, the 100k resistor works for the heatbed temp range, but you need a much smaller resistor for hotend temps. This is of course pretty easy, just need to hook up another resistor in parallel between +5v and the thermistor sensor input.

Then you'll need a new thermistor table.

But I don't see how you would do all this without having access to a mightyboard.

To sum it up, other than using a thermocouple, there are no easy options for you.

I don't plan on using the hbp thermistor input, I was simply illustrating that the mechanism is already in place within sailfish to use thermistors. A year ago or so, somebody wrote firmware to enable the gen3 electronics to support an extra set of step and direction pins. Same concept here.

I'm not trying to discourage you, just keeping it real ; )

There is support for reading thermistors in sailfish, but not for extruders. It's not just modifying a config file, but adding new functionality. And as I mentioned you will also need to modify the voltage divider.

For someone who has access to the hardware and is familiar with avr programming, modifying the firmware and testing would be a couple hours of work.