MK7

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MK7

Postby bdring » Sun Feb 26, 2012 9:09 pm

If you use the MK7 with RAMPS be sure to get a thermister. The default with MakerBot is thermocouple. that is not compatible with RAMPS.
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Re: MK7

Postby AndrewR » Mon Feb 27, 2012 6:54 am

I don't have a Arduino Mega/RAMPS with which to play with but there might be a way to combine the following to use an I2C connection. I'm all for the use of TCs due to their durability, ease of installation, and lack of calibrated look-up table. I've got a couple MAX6675 chips being delivered in the next few weeks, so I'll see what I can figure out with a basic Arduino and a Sanguino.

http://www.reprap.org/wiki/Hacks_to_the ... oller_v2.2
http://www.brokentoaster.com/blog/?p=561

Also, if you can scrounge up an old AD595 it can be used directly with an analog read pin: http://www.reprap.org/wiki/Thermocouple_Sensor_1_0
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Re: MK7

Postby Zat German » Mon Feb 27, 2012 12:59 pm

AndrewR wrote:I don't have a Arduino Mega/RAMPS with which to play with but there might be a way to combine the following to use an I2C connection. I'm all for the use of TCs due to their durability, ease of installation, and lack of calibrated look-up table. I've got a couple MAX6675 chips being delivered in the next few weeks, so I'll see what I can figure out with a basic Arduino and a Sanguino.

Adafruit offers a MAX 6675 library that only requires 2 digital inputs and 1 digital output, no analog required. I think that would be much simpler for my RAMPS build. I am just going to use their breakout boards. They also have a tutorial on getting it working that you can probably refer to.
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Re: MK7

Postby JeremyBP » Mon Feb 27, 2012 2:06 pm

I'm going the AD595 route with mine, and I kind of wish I had gone the MAX6675 route. It's cheaper and more accurate, not to mention smaller.
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Thermocouples

Postby bdring » Mon Feb 27, 2012 2:24 pm

I use a lot of temperature sensors at my day job. We use thermisters and thermocouples. Thermocouples are nice because they are cheap and easy to make, but they do have their issues. In my experience they tend to be a lot more noise sensitive. They work by two different materials generating a voltage proportional to temperature at the junction of those materials. The voltages are very, very low. Sometimes you can get an apparent step in temperature just by turning on a noisy circuit.
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Re: MK7

Postby JeremyBP » Tue Feb 28, 2012 4:37 am

For reference, a mk7 with 1/16 microstepping is about 100.32 steps/mm.
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Re: Thermocouples

Postby AndrewR » Tue Mar 06, 2012 4:05 am

bdring wrote:I use a lot of temperature sensors at my day job. We use thermisters and thermocouples. Thermocouples are nice because they are cheap and easy to make, but they do have their issues. In my experience they tend to be a lot more noise sensitive. They work by two different materials generating a voltage proportional to temperature at the junction of those materials. The voltages are very, very low. Sometimes you can get an apparent step in temperature just by turning on a noisy circuit.


Got my hands on the MAX6675 chips and RAMPS/MEGA setup. Time to start figuring out how to mash the two together. From a quick first glance, the Sprinter firmware already has some options for using a thermistor, AD595, or MAX6675 for the nozzle temp and options for a thermistor or AD595 for the bed temp. Don't know how well they're developed in the code yet. Not much info available on progress that was attempted back in 2010.

Found an novel solution to the AD595 amp setup with respect to signal noise generated from the switching power source. I've seen this noise on this same board and will most likely be integrating the RC filter on my board. These AD595 boards should be pretty easy to integrate into the RAMPS board given they are already pumping out an analog signal... just need to pull out the 10uF cap and 4.7K resistor for the desired RAMPS pins.

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Re: MK7

Postby JeremyBP » Tue Mar 06, 2012 4:30 am

I would suggest using one of the aux ports on the bottom of the RAMPs board and changing the pin in firmware. I would also suggest using the marlin firmware, as it stably supports the max6675 out of the box.
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Re: MK7

Postby AndrewR » Tue Mar 06, 2012 8:04 am

JeremyBP wrote:I would suggest using one of the aux ports on the bottom of the RAMPs board and changing the pin in firmware. I would also suggest using the marlin firmware, as it stably supports the max6675 out of the box.


After looking into schematics and digging into the Sprinter code, it looks to be quite a simple incorporation for RAMPS. I've yet to test my theory and will have to work it tomorrow night, but from what I can see, Sprinter is already configured to have the MAX6675 plugged into the AUX-3 port. I've just got to solder up my MAX6675 board to match the connectors and I'll be ready to go. Also the AD595 should be no problem using the AUX-2 analog ports which will negate the need to pull off the cap/resistor from the RAMPS board. I'll give the AUX-2/AD595 config a whirl too. I'll be sure to write this up in a new thread once working... hopefully this isn't too much of a thread hijack since it's getting TCs working for extruders. ;)

As for marlin, I've only started to use the Sprinter firmware and haven't looked into other loads yet. Sprinter was the only firmware I could get to quickly work with the Sanguino and the old Gen 3 driver boards that I had from a few years ago. I'll definitely give it a shot once I get Sprinter+RAMPS+MAX6675+AD595 working. Thanks for the info.

Now a confession. I don't have a 3D printer yet and haven't been able to put any of this work towards the actual goal of reforming plastic to my will. I have both sets of electronics (Sanguino+Gen3 & RAMPS) working quite well and have most of the hardware bits for a Hadron-sized bot (and a 2.x laser!) but I can't seem to time my store.makerslide.com visits correctly to be able to order the MakerSlide rails. I would have joined in on the Hadron hardware kits but didn't want to shell out a couple hundred extra dollars for parts that I have sitting next to me. It's not a major issue yet since I'm still waiting for delivery of an extruder & hotbed... and I have a job... and other hobbies... and etc. ;)
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Re: MK7

Postby alwayswill » Mon Mar 12, 2012 11:00 pm

If it helps anyone, the MakerBot MK7 StepStruder is in stock again...
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