Official Luthiers Forum!

There have been a couple of great articles on making an electronic control unit for a side bending jig and I just can't find them in the archives. Any help directing me to those would be GREATLY appreciated.
I am working on some improvements in my current tooling and this is one of them. Thanks in advance.

-j.

_________________
“If God dwells inside us like some people say, I sure hope He likes enchiladas, because that's what He's getting”
-jack handy

Hi J.

Here are a few:
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=26461
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=19892
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=25297

Cheers
Rick

I have done this and if you have any questions feel free to PM me, the threads mentioned above will give you enough info to get started. I am a retired controls electrician from an auto plant paint shop and spent many hours maintaining and programming PID temperature controllers.

Fred

_________________
Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

Fred-
Do you have any info on sourcing a practical-shape and size thermocouple for a bending setup? Most of the ones I've found online seem to be 1/4-20 or bigger. Something nice and flat to tuck under the blanket/wood would be just the thing.

Cheers
John

I use a piece of type K thermocouple wire stripped and twisted together at the end, it fits between the blanket and slat better than the one that came with my controller and is a little quicker to respond as there is less metal to heat and cool.

Fred

_________________
Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

Fred-
What's the easiest source for that wire? Buy another type K thermocouple and 'hack' it?
John

I just cut my TC wire in half and now have 2 the wire was plenty long. I wish I had been doing this when I was still working we had both type J and K wire in huge rolls, as it has to go from the location of a thermocouple back to the controller sometimes very long runs.

If you are interested in how they work read this.
http://www.capgo.com/Resources/Temperature/Thermocouple/Thermocouple.html

These leaf style thermocouples might be real good for our use in bending blankets.
http://www.microdaq.com/thermocouples/leaf.php

Fred

_________________
Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

Thanks, Fred.

I came across this simple and cheap thermocouple http://www.auberins.com/index.php?main_page=product_info&products_id=144 it will fit in the blanket slats wood stack real well and is a little stronger than a twisted wire TC.

Fred

_________________
Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

Fred--Would you happen to know of a source for a switchable input box for inputting different probes into a single input PID controller?
Maybe this is not possible but would like to use probes at two or three different locations on the side being bent.
For example, the first probe input would be used for bending the lower bout, the second for the waist and third for the upper bout and/or cutaway.
This scenario would involve short heat blankets for the area being bent.
Thanks
Nelson

Google shows a few sources -- http://www.google.com/products?hl=en&as_epq=&as_oq=&as_eq=&num=100&lr=&as_filetype=&as_sitesearch=&as_qdr=all&as_rights=&as_occt=any&cr=&as_nlo=&as_nhi=&safe=off&q=thermocouple+switch&um=1&ie=UTF-8&ei=JZinS9ChGo_YNdis1YUD&sa=X&oi=product_result_group&ct=title&resnum=1&ved=0CCAQrQQwAA

But in my opinion, thermocouple plugs/jacks (appropriate to your type of TC & TC extension wire) might be a better solution. Much lower cost, takes up less space. Unplugging/plugging something else isn't that much of a pain unless you're doing it dozens of times an hour or if the plug's inaccessible. YMMV.

The issue with switching Thermocouples to a single input is the fact that the metal alloy of each wire must match all the way to the input terminal, so any switches would be very expensive and dedicated to one type of couple. one way to do this is to put a dedicated connector on each couple and a single matching connector on the input of the controller, again matching the polarities all the way to the controller. I have moved my digital thermometer around to different locations and the readings don't vary much.

I suggest reading the article at the link I posted above to get a little background info on thermocouples. They are very simple but must be used right, we used to have issues at work when careless coworkers would change out a couple with the wrong type causing huge inaccuracies or switching the polarity of the leads. I spent many unhappy hours sweating on top of the paint ovens repairing these type of mistakes, which we wouldn't see until the oven was hot.

Fred

_________________
Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

Fred and Christopher
Using either of the two methods mentioned above, what type of receptacle is available to adapt to the screw type connectors on the PID?
Now I'm using a miniature K type plug by twisting each of the two prongs 90 degrees and inserting into these connectors on the PID.
(Jury rigged, I know)
Thanks for all your help, guys!
Nelson

Edit: Do these jacks/receptacles require the same type couple wire even if it's just a couple inches length?
http://www.davis.com/catalog/product_view.asp?sku=0887876
http://www.davis.com/catalog/product_view.asp?sku=9384053

You can cut off the connector and screw the wires directly to the terminals or take the pins out of the plastic casing to screw to the terminals. Once you get to the terminals as long as the wires are not reversed either way will work fine. I cut my connector off as I made 2 thermocouples out of one as it had a way longer cable than I needed.

Fred

_________________
Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

http://www.davis.com/catalog/product_view.asp?sku=0887876
Fred, what I'm wondering is if the special couple wire is required to connect this receptable to the PID even if they're located next to each other in a panel?
Thanks
Nelson

The thermocouple wire of the type of the couple is normally connected all the way to the controller so I would do that, though if it is really close you might get away with it. I would try it if you want and compare the results to a digital thermometer up to the range of the heat needed to bend. A few degrees difference should not be a huge issue while bending as we can adjust our set point with the error in mind.

Fred

_________________
Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866