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RAMPS with Thermocouple

Posted by Grogyan 
RAMPS with Thermocouple
December 30, 2010 07:12PM
I've been bored waiting for the holidays to finish so I can go and use the drill press at work after hours, to hopefully get the Y axis gantry, anyone following my story will know.

I ordered parts for a Mendel as a backup plan, and that plan also involves new electronics, which I started to work on int he last couple of days.

Essentially I have already added the MAX6675 thermocouple sensor, added a resistor to the power LED (something that should not have been forgotten), cleaned up a lot of traces, removed even more vias that served no purpose.

The addition of the thermocouple comes at the loss of one of two thermistor sensors.

My plan from here on out is to also investigate adding connectors for the motors, instead of straight off the A4983 Polulu stepper driver (without onboard power regulation (Polulu sells two varieties of the same board, so I am just mentioning it here just in case someone wanted to know)).
More importantly i'm clearing up, or trying to, clear up the clearnace issues from polygon planes, however Eagle being the problem program it is won't let me even select it.

I want to clear up more traces and vias, but before I do, i'd like the designer to explain why he/she chose to have seperate holes, as there is no problem in placing wire links from soldered areas of pins to other pins instead of separate holes.

I will also investigate the the feasibility of tricolour LEDs on the Step and Dir pins of each driver board, to give visual feedback on the machine. Besides everyone likes blinky lights.

I will look at the possibility of replacing the jumpers with jumper pads, where just applying solder to them will enable the same effect, with less holes to drill.

The RAMPS page also wants to add in the future another extruder driver, this cannot be done, as there is no space left on the board. However it dawned on me late last night, that there is nothing stopping from having another board tiered above, this is a good idea, and probably will work well with a feedback LCD screen and maybe even a microSD card slot.
These are nice things but will have to wait a bit befoe someone tackles them.

Beofre I go, anybody got a clue as to how to select polygon planes, i've tried almost everything and still can't select them?

Edited 1 time(s). Last edit at 12/30/2010 07:12PM by Grogyan.
Re: RAMPS with Thermocouple
December 30, 2010 07:45PM
Seems like it is an indicator for DRC error checking, so I have altered track spacing to be a minimum of 0.4mm, doesn't seem like much but a RepRap should be capable of this precision.

Still working on it, lots of errors to fix, makes me wonder if JohnnyR did any sort of checking.
Re: RAMPS with Thermocouple
December 30, 2010 08:53PM
The polygon is generated based on your DRC settings. After you set the clearance measurement in DRC and run ratsnest it will automatically set the polygon spacing to that width.

You can select the polygon by clicking on it's outline. The gnd polygon on RAMPS shares it's outline with the dimension line. You can left click on the outline and then right click to cycle through the objects you are selecting.

I run a couple passes of DRC for these first generation "RepRappable" etch resist designs. I try to get 7mm clearance on all the traces I can. Then I make sure that the stuff I couldn't fit with 7mm clearance do have 6mm.

The extra vias are to make it easy to use a single sided pcb for home fabrication. They make it much easier to run the top wires.

The resistor for the LED is already built into the Arduino's D13 pin for out of the box projects, so it is not needed.

I have a 1.2 version of RAMPS in fab now. It should be tested with files available any day now. I squeezed connectors for the motors onto the RAMPS shield instead of having to connect on top of the drivers, cleaned up a few left over ugly traces, and a few other minor annoyance patches.

I almost have a shield designed to go under the RAMPS with much of the wishlist included. Well I have most of the schematic done. I have AD595 on for thermocouple. Is there a reason it would be better to go with MAX6675?

I added the extra breakout pins to be as flexible as possible with future expansion (HACKING).
Re: RAMPS with Thermocouple
December 30, 2010 11:10PM
Hello JohnnyR, glad to hear there is a 1.2 in the works.
I would still put a resistor on the LED anyway, though the uC should sink not source the LED, so having the extra resitor means that there is very little chance of doing damage to the uC.

I have been hacking away at improving a number of items on RAMPS, though I haven't got to putting on connectors, that I think is next on my list.

Yeah, lol, I realised when I was working on the board that it was just showiing the DRC errors, not the top and bottom layers.

The first time I ran the DRC check it came up with over 1000 problems, 600 of those were just interferece problems with the stop mask, so can be ignored.

Personally i'd like to stay away from through hole as much as I can, and if someone wants to do some hacking there is plenty of space underneath to do that, plus having a proto shield tiered above.

The MAX6675 is a newer device that essentially relaces the old AD595, surface mount only, that is ok, managed to place that on the underside of the board.

Another note about the MAX6675, is that it gives a good benchmark for RepRapping circuits to any modest level of detail, ie SO-8 type pitch is common, however more modern devices are even smaller, so its important to make sure that the RepRap can print to that level of detail in the future.

On my board, I have only 2 wires that don't have vias in them, I removed those today, but can put them back.

There is still interference issues with jumpers, which you should have noticed as well, i've ignored the error, but eperince with similar tolerances at work means shorts are likely, hence i'd like to do away with header jumpers.

Are you by chance printing them out on a RepRap yet? Cause I know that these issues won't be here for comercial PCB manufacturers, and that's is why i'm liking the RAMPS, it can be/should be printed on a RepRap.

I'm working on the assumption of a pen with a 0.7 nib/tip with at least a 0.4mm space, though most are more than that, only working around the MAX6675 has issues with clearance.

The connectors i'd like to use are the same molex connector as is used on the Makerbot, its a comon connector, that or a locking header connector, both types have the locking feature, which is important for long term use of the machine.

I'm thinking that it might be a good idea to share, and run through each others work, see what issues there may be.

Edit1: Posted what i've been working on in the last couple of days.
Edit2: The posted files don't have polygons around the board, this is deliberate, and will be put back later once i've worked out how to put connectors on. Added my opinons of the connectors to use as well.
Edit3: Removed my comment about I2C, this is my mistake, the device works over SPI.

Edited 4 time(s). Last edit at 01/02/2011 11:22PM by Grogyan.
open | download - RAMPS-1.2-Grogyan.zip (92.6 KB)
Re: RAMPS with Thermocouple
December 31, 2010 12:51AM
Yes, I have printed both versions that I have published. Many of the pictures on the RAMPS wiki page are of RAMPS boards I printed on my Mendel. . There is also some narration on the UltiMachine blog.

Surface mount is definitely good stuff. RAMPS has so many headers, connectors and, sockets that have to be through hole it kinda makes sense not to use SMT on the few remaining components(with the resolution I experienced with a sharpie marker). I expect we can get quite a bit more resolution with [www.sakuraofamerica.com] , like the guys used printing transistors.

Thanks for sharing your files (and ideas). Covered up for a day or two, but I will give them a look this weekend.
Re: RAMPS with Thermocouple
December 31, 2010 01:21AM
He he, whoops, made a mistake on my board.

Reading the datasheet helps when knowing which logic to use for sleep and reset.
Re: RAMPS with Thermocouple
January 01, 2011 05:04PM
I fixed that problem, plus doing some changes today, including making space for locking header connectors, but becuase of space requirements they will be the standard 0.1" type.

I'm keen on seeing what JonnyR releases, he already changed the wiki, and removed my comments, fair enough.

I'll be plodding along with this all day.
Re: RAMPS with Thermocouple
January 01, 2011 08:06PM
I'm leaving it for the day, as i've just about completely rerouted the board, with a number of differences from the last one I posted.

Things I have succeded in doing.
Standard 0.1" loching headers for the motors
Jumper pads instead of headers
Doubled the use of the 100K pull ups, which were pulling down, datasheet suggests using pullups on logic high pads.
Rearranged the FETs for possibility of affixing a heatsink
Many more subtle changes, thus once i've done this, it will have a different pinout compared to the old version RAMPS and probably JohhnyR's as well.

Failed in reducing the number of wire links, there are 11 in total, 3 of which are data, I was trying to avoid having no data wire links.

Again feedback is welcome.
Re: RAMPS with Thermocouple
January 02, 2011 10:29PM
The MAX6675 does not communicate using the I2C protocol but in fact it uses the SPI protocol. These two protocol use completely different ports on the Arduino and are different in the way they transmit information. Luckily the chip is wired to the correct pins, yet it might be confusing to people new to electronics and mislabeling can cause problems further down the line.

Otherwise, the board looks great.

Edited 2 time(s). Last edit at 01/02/2011 10:35PM by ZNahum.
Re: RAMPS with Thermocouple
January 02, 2011 11:19PM
Good point.

It's funny how everytime I see it says SPI I think of I2C.

I'll edit my posts to reflect this blunder, one of many.
Re: RAMPS with Thermocouple
January 04, 2011 07:23PM
Looks like JohnnyR made some good improvements over on the wiki, first thought no thermocouple as standard.

I'll have to see about getting my blog added to the blog of blogs and blog about this on my blog, then I can be a real blog-head, lol cool smiley
Re: RAMPS with Thermocouple
January 04, 2011 09:55PM
Hi Grogyan, thanks for noticing my efforts.

One thing I notice about your design that will probably catch you by surprise. The fuse footprint is not the same as the actual part. I used a stock littlefuse footprint. The part overhangs it some and probably interfere with the mosfet.
Re: RAMPS with Thermocouple
January 15, 2011 04:00PM
Made more progress, just got to make a new fuse part for the library, then the board is off to get fabbed.
Re: RAMPS with Thermocouple
February 06, 2011 06:04PM
Forgot to post, update.

My version has finished being designed 2 weeks ago, but I do not have any money or a RepRap or transfer method to fabricate the board.
I have also been busy, both at home and at Tangleball and forgot to upload the design.

I may remember tonight after work however if someone really wants it ASAP then please pm me, to remind me to upload it.
Re: RAMPS with Thermocouple
February 20, 2011 07:21PM
I would be interested in seeing the eagle files for this board.

Would you be happy to post them? Also have you considered firmware for the 6675? i have just started looking into it and trying to work out whats the besty option for a ramps with 6675 board. i was considering an addon to johnny's board but this might just make it alot easier

Re: RAMPS with Thermocouple
February 21, 2011 11:04PM
Just remembered to do this on the way home from work today.
Will let you know when the files have been uploaded.
Re: RAMPS with Thermocouple
February 21, 2011 11:57PM
I have created a page, much of it is copied from the original page.

I will update it, or anyone else can, as time goes by and board has been thoroughly tested.


My apologies I have to log right now, Christchurch earthquake, I live in Auckland.

Edited 1 time(s). Last edit at 02/21/2011 11:57PM by Grogyan.
Re: RAMPS with Thermocouple
May 26, 2011 09:08PM
I'm trying to use the Sprinter firmware with a MAX6675. This is all new to me. How do I hook it up? I see the 6675, but commenting out the thermistor and uncommenting the 6675 doesn't quite cut it. What am I missing? What files should I be editing?
Re: RAMPS with Thermocouple
May 30, 2011 10:46PM
Just thought i would do a quick post to say i have a workign max6675 PCB that stacks on the end of any off the ramps boards. it is designed to work with the sdramps PCB.

I should be able to post up the eagle files in the next few days if theres interest.

at the moment im more worried about getting my wolfstrap working
Re: RAMPS with Thermocouple
June 15, 2011 05:40AM
I should have posted a long time ago.

I am currently busy workin on getting my current RepRap working under Gen3, so much time that I still have not got around to getting a PCB fabbed. Yes I am slow, and I do think about it every time I work on the RepRap every week.

Life is busy! But I have not forgotten about this little project.
I see that JonnyR has long since added to his a second extruder, still no thermocouple, meaning I will still ork on this.

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