Endothermic Task

[Unome]

See rule 4.b.ii for details.

Seems pretty standard, I believe the same thing (or something similar) was around in 2011. I have no idea how one would go about doing this though.

[RJohnson]

I'm wondering if we could use an arduino temperature probe, or similar, for this. Will have to submit FAQ.

[andrew lorino]

My best idea is to dissolve a salt with a positive heat of solution into water (currently leaning towards KCl), lowering the temperature, and then... doing something. Thermocouple? Diffraction? Really sensitive bimetallic strip? Suggestions would be much appreciated. Disclaimer: My Arduino experience extends only to frying them, so a more analog approach would be preferred.

[Dark Sabre]

I spent 15 minutes trying to find an old picture before realizing that I'd documented the machine already on the wiki...
2004_DarkSabre_MPC Wiki
Scroll alllll the way down to step 15 and the line above it as a possible example.

You can easily get the chemical cold packs from the grocery store, which at least used to contain Ammonium Chloride. You just have to mix it with water. At the time I sensed the temperature change with a Lego RCX (since this is 2004 we are talking about) temp probe. If I were repeating it today, I'd definitely be using an arduino.
Agitation will speed up the reaction and thereby make it more consistent, but it is probably never going to be the most precisely timed part of your machine.

If you are into a more electromechanical approach, you could consider using a bimetallic thermostat. Digikey carries a line of them at different set-points. Something like this 15deg C one might be useful. Please note that these particular models are not waterproof. Depending on just how cold your reaction gets, it might take a little while to respond.

From a purely mechanical perspective, you could definitely use a bimetallic strip or coil. If speed of response is an issue, you might considering cooling down a hot bimetal so you have a larger temperature differential.

Thermocouples are going to be troublesome since you need to have significant gain to sense the voltage, but worth it in terms of the thermal mass of the sensor.

Worth noting that you definitely don't need to have a reaction going on...
Just touching an ice cube to something at room temperature would be an endothermic process, since the ice would be absorbing heat energy from the thermistor/bimetal/etc. Same goes for say blowing room temperature air across a hot thermistor/bimetal/etc. The absorption of heat energy into the relevant medium causes a drop in temperature.

There are definitely a lot of options. It will be interesting to see what the most reliable ones turn out to be.

[ScottMaurer19]

I spent 15 minutes trying to find an old picture before realizing that I'd documented the machine already on the wiki...
2004_DarkSabre_MPC Wiki
Scroll alllll the way down to step 15 and the line above it as a possible example.

You can easily get the chemical cold packs from the grocery store, which at least used to contain Ammonium Chloride. You just have to mix it with water. At the time I sensed the temperature change with a Lego RCX (since this is 2004 we are talking about) temp probe. If I were repeating it today, I'd definitely be using an arduino.
Agitation will speed up the reaction and thereby make it more consistent, but it is probably never going to be the most precisely timed part of your machine.

If you are into a more electromechanical approach, you could consider using a bimetallic thermostat. Digikey carries a line of them at different set-points. Something like this 15deg C one might be useful. Please note that these particular models are not waterproof. Depending on just how cold your reaction gets, it might take a little while to respond.

From a purely mechanical perspective, you could definitely use a bimetallic strip or coil. If speed of response is an issue, you might considering cooling down a hot bimetal so you have a larger temperature differential.

Thermocouples are going to be troublesome since you need to have significant gain to sense the voltage, but worth it in terms of the thermal mass of the sensor.

Worth noting that you definitely don't need to have a reaction going on...
Just touching an ice cube to something at room temperature would be an endothermic process, since the ice would be absorbing heat energy from the thermistor/bimetal/etc. Same goes for say blowing room temperature air across a hot thermistor/bimetal/etc. The absorption of heat energy into the relevant medium causes a drop in temperature.

There are definitely a lot of options. It will be interesting to see what the most reliable ones turn out to be.

I was wondering when someone would figure out the ice pack idea...

[andrew lorino]

With something like this you could make whatever goes to the speaker go to an SCR instead, no programming required...

[dbli2000]

Just to clarify, touching an ice cube to a temperature sensor would count as an endothermic action?

[ScottMaurer19]

Just to clarify, touching an ice cube to a temperature sensor would count as an endothermic action?

According to the coaching academy, yes.

[Snarknado]

Just to clarify, touching an ice cube to a temperature sensor would count as an endothermic action?

According to the coaching academy, yes.

Good luck keeping an ice cube all the way from impound.

[ScottMaurer19]

Just to clarify, touching an ice cube to a temperature sensor would count as an endothermic action?

According to the coaching academy, yes.

Good luck keeping an ice cube all the way from impound.

Try keeping it overnight when traveling