Contactor/ PID question

[Grumple]

Ed,
Things must be slow...you are looking for old threads to do followups. Just kidding.... That is a good and easy solution to the problem. There is always a way.
Grumple

p.s. Did anybody else notice that RatShack parts quality has gone down lately? Or were they always that bad?

[ed_denu]

Hi Dave, Things have been a little slow recently.

I was messing around with a dpst switch and a digital temp display when I recalled this discussion. I realized that this was the solution to the problem.

This probably should be a new post, but what I was working on is a small box with a digital temperature unit mounted within along with a dpst switch. There are 2 'K' type thermocouplers mounted to the switch, then fed to the display. I can attach the ends of the thermocouplers to parts within the oven with alligator clips and get actual temperature readouts of 2 different parts via the display.

Not my idea initially, I was just following up on a post in another forum. Here is a picture of the unit:

[Grumple]

Hi Dave, Things have been a little slow recently.

I was messing around with a dpst switch and a digital temp display when I recalled this discussion. I realized that this was the solution to the problem.

This probably should be a new post, but what I was working on is a small box with a digital temperature unit mounted within along with a dpst switch. There are 2 'K' type thermocouplers mounted to the switch, then fed to the display. I can attach the ends of the thermocouplers to parts within the oven with alligator clips and get actual temperature readouts of 2 different parts via the display.

Not my idea initially, I was just following up on a post in another forum. Here is a picture of the unit:

Hey Ed,
That looks like an interesting project. Do you mind sharing the original link or a parts list and schematic? I want to make one of those for sure. Looks very useful along with the IR gun.
Thanks,
Grumple

[ed_denu]

It's really very simple. Here is the parts list:


Digital temperature meter from ebay seller - He sells different types of meters, so be sure to get the one you desire. This one is a DC input power, but he also has AC and C or F meters.
Digital DC Temperature Meter for K Type Thermocouple(F) - eBay (item 250469366259 end time Jul-28-09 06:41:35 PDT)

(2) 'K' type thermocouplers from the same ebay seller. These are available in several different lengths. I used the 3m versions.

(1) outdoor single gang box - available at any of the home improvement stores.

(1) solid stainless box cover. I cut the opening for the meter with a Dremmel tool and small cutoff wheels. Hole for switch was drilled with a step drill.

(1) DPST on/on switch from Futurlec. These are available many places

(2) Alligator clips from Futurlec

(1) Used 12V plug in transformer from spare parts bin

The meter snaps into the opening cut in the cover plate. On the thermocouplers, I cut the mounting nut off the hot end, again with a Dremmel and cutoff wheel and attached an alligator clip. I cut about 6 inches of wire off the cold end of the TC. Each TC then gets mounted to the switch. I soldered the connections but you could use crimp terminals. The 6 inch piece gets mounted on the center lugs of the switch and then goes to the meter. Be sure to keep the relationship of the colored wires or the TC will not report correctly. Finally I glued a large round magnet to the rear of the box so I can mount the unit anywhere on the oven.

I tested the meter and TCs in cold ice water and they read around 35 degrees. I tested it again after adding the switch and both TC's still read about 35 degrees, so the addition of the switch doesn't appear to materially affect the temperature reading. I'm doing a little testing with the clips attached to parts and using the IR gun as an additional gauge.

Mr Duke over on the PBTP site initially discussed this concept and he is making/selling these if you would just want to purchase one. Here is the link:
PowderBuyThePound.com • View topic - U can make it and you really need it!

[Grumple]

It's really very simple. Here is the parts list:


Digital temperature meter from ebay seller - He sells different types of meters, so be sure to get the one you desire. This one is a DC input power, but he also has AC and C or F meters.
Digital DC Temperature Meter for K Type Thermocouple(F) - eBay (item 250469366259 end time Jul-28-09 06:41:35 PDT)

(2) 'K' type thermocouplers from the same ebay seller. These are available in several different lengths. I used the 3m versions.

(1) outdoor single gang box - available at any of the home improvement stores.

(1) solid stainless box cover. I cut the opening for the meter with a Dremmel tool and small cutoff wheels. Hole for switch was drilled with a step drill.

(1) DPST on/on switch from Futurlec. These are available many places

(2) Alligator clips from Futurlec

(1) Used 12V plug in transformer from spare parts bin

The meter snaps into the opening cut in the cover plate. On the thermocouplers, I cut the mounting nut off the hot end, again with a Dremmel and cutoff wheel and attached an alligator clip. I cut about 6 inches of wire off the cold end of the TC. Each TC then gets mounted to the switch. I soldered the connections but you could use crimp terminals. The 6 inch piece gets mounted on the center lugs of the switch and then goes to the meter. Be sure to keep the relationship of the colored wires or the TC will not report correctly. Finally I glued a large round magnet to the rear of the box so I can mount the unit anywhere on the oven.

I tested the meter and TCs in cold ice water and they read around 35 degrees. I tested it again after adding the switch and both TC's still read about 35 degrees, so the addition of the switch doesn't appear to materially affect the temperature reading. I'm doing a little testing with the clips attached to parts and using the IR gun as an additional gauge.

Mr Duke over on the PBTP site initially discussed this concept and he is making/selling these if you would just want to purchase one. Here is the link:
PowderBuyThePound.com • View topic - U can make it and you really need it!

Thanks Ed,
The first thing I thought of was the resistance of the TC wire going crazy because of the switch and or solder connections. Then I read the link you posted and it seems it doesn't matter (that much) so that is good. I ordered 2 TC's from Auber for my build and I mentioned to him that I was going to switch the TC and split my oven. He suggested some special plugs made just for TC's so I bought them. I haven't tried them yet as my oven isn't ready yet but I have been working on it. Just been multitasking too much! You are sure getting your moneys worth out of that PDF maker you use.
Thanks,
Grumple

[ed_denu]

What are the special plugs you referenced for TC's?

Yes, the PDF creator works really well. It installs as a printer device, so you can output to PDF format from any print screen. I use Autocad for drawing schematics, etc., but most forums and sites won't accept dwg files, so the PDF creator comes in very handy.

[Grumple]

Ed,
Here are the plugs I was talking about:
Panel mount connector for K thermocouple [TCCON] - $4.90 : auberins.com, Temperature control solutions for home and industry

Grumple