Temperature Task

[Paradox21]

So if it is the second to last task, the battery will be heating it up the whole time the device is running right? Doesn't that take up a lot of juice from the battery?

Just a reminder, you can't use any electricity after the sand timer task. So unless your device doesn't have a sand timer task, you will have to put the task earlier if you plan to use a battery. I do my temperature task as the second task, to prevent killing my batteries.

[illusionist]

Yeah, i realized that, just gave a random example. So if you were using a 6V battery, how long does the battery last? I mean, how many test runs can you do? I think I might put it in early too to save some juice.

[Paradox21]

Yeah, i realized that, just gave a random example. So if you were using a 6V battery, how long does the battery last? I mean, how many test runs can you do? I think I might put it in early too to save some juice.

If you plug it in immediately before you start your run, it only needs to be on for a few seconds. With that duration, a single battery pack could last the rest of the season. But we inevitably forget that it is turned on at times and it all drains in a couple minutes. But overall this year, I have not gone through nearly as many batteries as last year, so it's not too bad.

[Primate]

Yeah, i realized that, just gave a random example. So if you were using a 6V battery, how long does the battery last? I mean, how many test runs can you do? I think I might put it in early too to save some juice.

Definitely. Make it your second or third task, if you can. It shouldn't much matter for this year's tasks, though; my guess is everyone has the first eight tasks, which only take four or five seconds (so who cares where you put it), then sand timer for a minute, then balloon release.

Those 6V batteries have a lot of juice. We used one in an electromagnet last year that lasted for 15ish minutes. If you shut it off first thing in your device, you really shouldn't have to replace it until competition. (Note: High school physics departments often buy lots and lots of these batteries. Go mooch.)

[illusionist]

Well... I got a meat thermometer, took it apart (or should I say broke it apart), and to my disappointment found that it had a curly bimetallic strip inside. It is about 4 inches long, pretty thin, and curled up like a spring. I'll pass some current through it later, but has anyone else found success with these? Is there any way for me to make use of this thing?
Edit: I ran electricity through it and it started to make smoke... I'm guessing that's a bad thing... Oh, by the way Primate, it was a Acu-rite thermometer.

[Primate]

Well... I got a meat thermometer, took it apart (or should I say broke it apart), and to my disappointment found that it had a curly bimetallic strip inside. It is about 4 inches long, pretty thin, and curled up like a spring. I'll pass some current through it later, but has anyone else found success with these? Is there any way for me to make use of this thing?
Edit: I ran electricity through it and it started to make smoke... I'm guessing that's a bad thing... Oh, by the way Primate, it was a Acu-rite thermometer.

If you're using an Acu-Rite meat thermometer, maybe it'll work better. The outdoor dial Acu-Rite I had wasn't actually a bimetallic strip--it was just a plain old metal curl that required serious heat to move.

You might have better luck with a two inch strip. Unbend it, then curl it into a 90-degree arc. Run current through it, and it should uncurl. (Smoking isn't necessarily bad, just be careful!)

[NinjaChicken]

Would you be able to run a current through a bimetallic coil to have it heat up, then break the current and have it cool down? Or is a nichrome wire necessary?

[buzzbuzz]

I've heard of a team doing running a low voltage current through a coil, but it took maybe 15 seconds for it to cool down.

[illusionist]

Ninja, what my team and many other teams have done is to have a 6V battery hooked up to the bimetallic coil. It is always running, and when a switch is hit, it turns of the current going to the coil. The coil then cools down and uncurls.
As to the time, I used a rather thin coil, so it cools down in about 9 seconds. Depends on the type of coil and its thickness
Btw, you want to use the big square 6V lantern batteries, as they last much longer.

[NinjaChicken]

Ninja, what my team and many other teams have done is to have a 6V battery hooked up to the bimetallic coil. It is always running, and when a switch is hit, it turns of the current going to the coil. The coil then cools down and uncurls.
As to the time, I used a rather thin coil, so it cools down in about 9 seconds. Depends on the type of coil and its thickness
Btw, you want to use the big square 6V lantern batteries, as they last much longer.

Ok I think I'll do that. How long on average does it take for the charge to start fading?