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SainSmart MAX31855 with RAMPS?

Posted by 3DTOPO 
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3DTOPO
SainSmart MAX31855 with RAMPS?
September 07, 2015 10:59PM
Does anyone know if its possible to use the SainSmart MAX31855 thermocouple amp with RAMPS? I am running Marlin.

SainSmart MAX31855
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3DTOPO
Re: SainSmart MAX31855 with RAMPS?
September 07, 2015 11:15PM
One more related question; In the Marlin Configuration.h file it states the following:

//// Temperature sensor settings:
// -2 is thermocouple with MAX6675 (only for sensor 0)
// -1 is thermocouple with AD595

Does that mean I can only use one MAX6675 chip on Sensor 0 only? In other words can I use MAX6675 (or compatible) on TEMP_SENSOR_0, TEMP_SENSOR_1 and TEMP_SENSOR_2?
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o_lampe
Re: SainSmart MAX31855 with RAMPS?
September 08, 2015 04:07AM
The MAX31855 is rated 3-3.6V, which would require a level-shifter.
It is more suitable for Due or other 32bitters.
-Olaf
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3DTOPO
Re: SainSmart MAX31855 with RAMPS?
September 08, 2015 10:14AM
Thanks Olaf. Bummer - I should have checked before I ordered.

What about the MAX6675, can more than one be used, or can it only be used for Sensor 0?
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dc42
Re: SainSmart MAX31855 with RAMPS?
September 08, 2015 12:29PM
The MAX6675 is an obsolete chip, replaced by the MAX31855. But you can still pick up MAX6675 modules on eBay.

MAX31855 support is currently being added to RepRapFirmware for Duet electronics, and I believe it is already supported in Smoothieware.


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].
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3DTOPO
Re: SainSmart MAX31855 with RAMPS?
September 08, 2015 12:35PM
I need something RAMPS 1.4 compatible since that I was I am working with. It may be obsolete but they are readily available on Amazon: SainSmart MAX6675 Module

I can get that for $14 including 2nd day shipping.

I only see two thermocouple amps listed in the Marlin config file, and I don't see any AD595 modules readily available. So are there any other supported besides the MAX6675?
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3DTOPO
Re: SainSmart MAX31855 with RAMPS?
September 08, 2015 01:33PM
Hmm actually apparently the AD595 only works to 500C and the 6675 only to 1024C.

I actually need to go a bit hotter than that so what would be involved with getting the MAX31855 running on RAMPS? Can anyone point me to how to build a level-shifter? I am not an electronic designer but can read simple schematics...
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dougal1957
Re: SainSmart MAX31855 with RAMPS?
September 08, 2015 01:54PM
OMG

Why do you need to go above 1024 degrees C that is enough to melt Aluminium Brass and Copper and probably to get Steel to a fairly soft consistency that it can be forged to shape
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3DTOPO
Re: SainSmart MAX31855 with RAMPS?
September 08, 2015 02:09PM
Yup I realize how hot that is.

winking smiley
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dc42
Re: SainSmart MAX31855 with RAMPS?
September 08, 2015 02:48PM
You would need to shift 3 signal levels down from 5v to 3.3V and one up from 3.3V to 5V. The down shifting can be done by a voltage divider, and the up shifting by a level shift chip or a non-inverting 74HCT-series gate such as 74HCT08. But as you are obviously not building to a tight budget, I suggest you ditch the ancient Arduino/RAMPS and get decent modern electronics instead.

Edited 1 time(s). Last edit at 09/08/2015 02:49PM by dc42.


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].
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3DTOPO
Re: SainSmart MAX31855 with RAMPS?
September 08, 2015 04:02PM
BTW: Here's what my RAMPS board looks like configured to control 5KW of power on redundant SSRs - with alarm! Everything tested and working - just need to figure out the thermocouples. :'(


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3DTOPO
Re: SainSmart MAX31855 with RAMPS?
September 08, 2015 04:09PM
Hmm apparently a pull request has been made to Sprinter for the MAX31855?

gitgub:pinski1?SanguinololuThermocouple
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o_lampe
Re: SainSmart MAX31855 with RAMPS?
September 09, 2015 10:40AM
I wonder, what material the probe screw is made off to withstand 1350°C?

I´m not familiar with SPI protocol. Maybe it´s not capable of daisy chaining several clients or is slowing down marlins ISR too much?
-Olaf
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3DTOPO
Re: SainSmart MAX31855 with RAMPS?
September 09, 2015 11:10AM
I think the probe material is stainless steel. I wish I knew if it will only support one or more thermocouple on a RAMPs.

Here is the pull request for Sprinter for the MAX31855; surprised it never got accepted?

[github.com]
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3DTOPO
Re: SainSmart MAX31855 with RAMPS?
September 09, 2015 10:20PM
Hmm - oh well. Not worth the trouble when the Smoothie board does what I need. Would have been nice to save the $$$ (I am already over budget of course) but I guess that is the end of the thread for me.
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lynspyre
Re: SainSmart MAX31855 with RAMPS?
September 26, 2015 02:39PM
Quote
3DTOPO
Thanks Olaf. Bummer - I should have checked before I ordered.

What about the MAX6675, can more than one be used, or can it only be used for Sensor 0?

I've finally got my MAX6675 working on Marlin 1.1 RC1, still no luck in Repetier 0.92. Here i posted my experience with this module, i've reached 310ºC in less than a minute with fine tuned PID.

I got the thermocouple and module from chinese vendor on Amazon. Just modded the probe to fit into E3Dv6 thermistor hole. How do i did that?, easy, hehe, just saw-cutted the probe near the crimped part that lead to the cable, the tip just went out and the soldered tip showed up.
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