Temperature Task

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JTMess
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Re: Temperature Task

Post by JTMess »

Primate wrote:
JTMess wrote:Our team used a bimetallic coil from a thermometer with the needle still on it to complete a circuit. We were a little worried about the time it would take to cool enough, but we got with 3 secs of a minute at regionals.
Interestingly enough, the bimetallic strip is actually one of our most reliable transfers. Usually it's the sand timer and the balloon that are the issue.
We are going to try a breaker or thermal limit switch at states. The thermal limit switches should have much more accurate timing since they are factory made and guaranteed to operate within 5 degrees of their labels.
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abobick
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Re: Temperature Task and Light

Post by abobick »

Can we simply turn off a light bulb for the cooling temperature task? It is the decrease in temperature of the filament that turns off the light, which can then open a photo-resistor which can open a relay, etc, etc.
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Re: Temperature Task and Light

Post by Primate »

abobick wrote:Can we simply turn off a light bulb for the cooling temperature task? It is the decrease in temperature of the filament that turns off the light, which can then open a photo-resistor which can open a relay, etc, etc.
That's actually a genius idea. I don't see why it wouldn't count.
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Re: Temperature Task

Post by DeltaHat »

Primate wrote:
abobick wrote:Can we simply turn off a light bulb for the cooling temperature task? It is the decrease in temperature of the filament that turns off the light, which can then open a photo-resistor which can open a relay, etc, etc.
That's actually a genius idea. I don't see why it wouldn't count.
Be real careful when wording this. You need to be crystal clear on your transfer list exactly what is going on.
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Re: Temperature Task

Post by missionimpossible »

Sorry I'm an amateur at this but...

1) If you were using bimetallic strips, can you please clearly explain how you would make that work?
2) Also, what can the coiling of the strip do?
3) We can use dry ice and one of my teachers said that if you vertically embed a quarter into dry ice, the quarter will shake back and forth since it is melting the dry ice. I haven't tried this, but dry ice might work.
4) Also I'm not sure if this is possible, you know how hot air rises, and cool air sinks? Maybe if you applied that to something, for example (this prolly won't work, but just for the sake of explaining) a rubber cork, then somehow you made it really cold and it sinks (in water) and sets off a lever in the bottom. I don't know...
5) In the rules it states that compressed air does not work because other chemicals are in it, but say we get purely air into a compressed container, how would spraying that help to decrease the temperature?

Sorry this is super long to read :D
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Re: Temperature Task

Post by craZ4soccr »

How can you get a thermistor to work without using transistors? (since they're illegal, right?) We tried using a relay but the relay itself seemed to inconsistent in the amount of resistance needed to flip the switch...
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Re: Temperature Task

Post by ichaelm »

missionimpossible wrote:Sorry I'm an amateur at this but...

1) If you were using bimetallic strips, can you please clearly explain how you would make that work?
2) Also, what can the coiling of the strip do?
3) We can use dry ice and one of my teachers said that if you vertically embed a quarter into dry ice, the quarter will shake back and forth since it is melting the dry ice. I haven't tried this, but dry ice might work.
4) Also I'm not sure if this is possible, you know how hot air rises, and cool air sinks? Maybe if you applied that to something, for example (this prolly won't work, but just for the sake of explaining) a rubber cork, then somehow you made it really cold and it sinks (in water) and sets off a lever in the bottom. I don't know...
5) In the rules it states that compressed air does not work because other chemicals are in it, but say we get purely air into a compressed container, how would spraying that help to decrease the temperature?

Sorry this is super long to read :D
I can't give you detailed instructions for every single option, but the idea is that you need to somehow cool down the coil so that it moves and touches something, causing the next action. Some people use chemical reactions or coolants to cool down the strip. You can use a cold pack pressed up against the coil to cause it to move, which could press a switch or touch an electrode, completing a circuit for the next action. But some people need a much greater temperature change than a cold pack can provide. The alternative is to heat up the strip with electrical current, and then allow it to cool down in air. If you do use an electric heating system, you will need to either have a length of heater wire (resistance wire, most commonly nichrome) that heats up next to the coil, or you will need to allow a controlled amount of current to flow through the coil itself. You can control the current by controlling the voltage of the battery, or by wiring a high-current resistor in series. Once the heating up works, you need to have some way to sense the position of the coil. That can be done with a switch that the expanding coil presses, or an electrode that the end of the coil makes a connection with. Then, you will need circuitry to make sure that the next action is triggered only after the coil has heated up and cooled down again.

I don't know exactly how the quarter in dry ice thing works, so I can't answer that. Your next idea seems good; have you ever seen a Galilean thermometer? I think you'd want to use a device that works on that principal.

If a container contains only compressed gas and no liquids, then releasing the gas would not cause a change in temperature.
craZ4soccr wrote:How can you get a thermistor to work without using transistors? (since they're illegal, right?) We tried using a relay but the relay itself seemed to inconsistent in the amount of resistance needed to flip the switch...
Yes, transistors are illegal, which means amplifying the minute changes in the resistance in a thermistor due to a temperature decrease in order to trip a relay is almost impossible. Technically it's doable, but I wouldn't count on a relay as a precision voltage sensor. I think either you'd have to abandon the thermistor, or create such a huge temperature change that it could be easily sensed by a relay.
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Re: Temperature Task

Post by Kid-Delta »

Sorry to interrupt, would dry ice be consider as a hazardous material???? :?:
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Re: Temperature Task

Post by Primate »

Kid-Delta wrote:Sorry to interrupt, would dry ice be consider as a hazardous material???? :?:
Nope, dry ice is fine. Note the national FAQ on the subject.
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Re: Temperature Task

Post by Kid-Delta »

Ahhhh, thank you
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