www.TK560.com

[BlindSquirrel]

I am in the home stretch on my over/under based on the tutorial. I plan to do the wiring on the oven this weekend and I have a few questions...

1. What kind of wire did you use to tie the NiChrome element to the ceramic posts? Is it pieces of the NiChrome itself?

2. Is the NiChrome coil directly attached to the wing nuts at A, B, C, D and E?

3. Where did you attach the ground wire?

4. After stretching the NiChrome to 95.5" (total length, I assume), is that the only piece I'll need for the oven?

Thanks for the great tutorial, forum and help! I couldn't have done it with you!
_________________
BlindSquirrel
Prop-Making Blog
www.mydumbprojects.blogspot.com

[crashmann]

[BlindSquirrel]

[quote="crashmann"]One of the most important things is to ensure you have the same resistance for each segment between the terminal points (A to B = B to C = C to D = D to E) Take your readings BEFORE connecting the wiring underneath the oven! Otherwise, you will just be measuring the total resistance, not the individual segments.
[/quote]

Thanks Charlie!

I am a complete noob when it comes to this wiring biz. Could you explain how to "take a reading" (so a 8-year-old could understand)...do I need to hire someone who knows WTF they're doing to do this?
_________________
BlindSquirrel
Prop-Making Blog
www.mydumbprojects.blogspot.com

[AlterEgos]

[crashmann]

Ha-ha! No need to go hire a professional to measure resistance

If you have a multimeter (it measures voltage and other stuff) with two leads (one black, and one red) set it to measure resistance - turn the dial to the greek omega symbol Ω

Here's my favorite image showing a test mounting of nichrome wire and measuring the resistance of the very short section:


Touch one lead (red) to one end of the nichrome wire, and the other lead (black) to the other end of the nichrome. This will give you the resistance for the complete 95" of nichrome (make sure the wire doesn't touch itself while you're taking the reading).

Now, divide this total number by 4, and that is the resistance for each segment (wingnut to wingnut).

Again, touch one lead (red) to the end of the wire, then touch the black lead 23" down the wire.

You should get a reading real close to "total resistance / 4"

Move the black lead to adjust the amount of resistance until you achieve the calculated value. Mark the wire with some tape.

Repeat this process starting from the tape, and continuing down the wire until you reach the end.

The wire will connect to the wingnuts at each tape location, and you will have equal resistance on each segment!

Again, good luck, and if any of this was confusing, please ask more questions!

Charlie
TI-386

[BlindSquirrel]

Aaaaahhhhh! It all becomes clear! The 8-year-old thanks you!
_________________
BlindSquirrel
Prop-Making Blog
www.mydumbprojects.blogspot.com

[jegner]

Looks like the guys have already answered your questions.

[AlterEgos]

Charlie, that's friggin' brilliant!!!

Thanks for the excellent instruction... now off to test the resistance on MY machine!
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-John

[ANH trooper]

You'll find all the answers on this board John,these guys are great

-Paul.

[BlindSquirrel]

I am attaching the 95" coiled wire, starting at the center (E) and it only seems to reach "C". Do I add more wire or do I stretch it more to reach "A"?
_________________
BlindSquirrel
Prop-Making Blog
www.mydumbprojects.blogspot.com

[AlterEgos]

Hmmm, I don't know if I would try to make just one heating coil for the entire oven. I made mine according to the directions in Thurston James' book, by using four 22" pieces that were attached to each terminal point. And my oven works great so, you might want to rethink what you're doing.
_________________
-John

[BlindSquirrel]

According to the tutorial:

First I cut a 2' 1/4" [24.25 inches] length from the 5 feet of coiled wire, then cut it in half to make two 1' 1/8" [12.125 inches] lengths. I then marked the center of each length of wire at 6 1/16" with a Sharpie Marker. After that was done, I put the marked center on a nail, grabbed both ends and stretched the wire to 95 1/2".

I stretched out one of the 12.125" lengths to 95.5" and I get a reading of 37 ohms (as opposed to Jim's 20.1 reading).

Should I be aiming for a 20 ohm total coil length reading? If it's higher than 20, what does that mean in terms of heating (hotter? Cooler? Longer to heat up?)

Checking the infraredheaters.com site, the 10ft length of 22 gauge NiChrome wire is rated at 360 ohms or (I assume from my readings) 36 ohms per foot.

Any advice how to proceed from here?

Thanks!
_________________
BlindSquirrel
Prop-Making Blog
www.mydumbprojects.blogspot.com

[jegner]

Well, don't take my reading for face value. It was check when I did not know what the heck I was doing. First, it was suppose to NOT to be connected to the power wires, so that will have some effect on my overall reading.

Sounds, like if you did exactly what I did, you should be good to go. Hook it up, and attach to your 102G wire, and then check your ohms. If you get something close to mine, my guess is you are close.

Your mileage may vary.

Jim

[knightshade]

[BlindSquirrel]

Thanks for the great link...very helpful.

I spent the evening utilizing my 20-year-old high school math muscles and was able to answer some of my own questions.


AND THEN I found the oven calculator link in the FIRST POST. D'oh!!

At least it was a good double check!

BTW what wattage is everyone using for their oven (Or perhaps what is recommended?)

Thanks everyone for the help!
_________________
BlindSquirrel
Prop-Making Blog
www.mydumbprojects.blogspot.com