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Re: Temperature Task
Posted: February 28th, 2011, 2:48 am
by Flavorflav
ichaelm wrote:
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.
Haven't tried it yet, but our backup plan is to wire four or five thermistors in parallel. Each is supposed to go from 1.5K ohms to 25, which I would think would be enough to trip the relay, ganged up.
Re: Temperature Task
Posted: March 12th, 2011, 8:19 am
by ichaelm
This new FAQ is pretty interesting:
http://soinc.org/node/731
Re: Temperature Task
Posted: March 12th, 2011, 10:14 am
by bwy
Yeah, I'm not sure the whole nichrome/bimetallic strip thing meets the "spirit of the task" either
In which case I don't really see any way of doing this task. They're basically asking for ice cubes or cold packs... to do what?
Re: Temperature Task
Posted: March 12th, 2011, 6:34 pm
by illusionist
As someone else pointed out:
Using dry ice, place a quarter/other object vertically partially embedded in the dry ice, and when the ice melts (it melts very rapidly) it will cause the quarter to vibrate side-to-side.
Re: Temperature Task
Posted: March 12th, 2011, 9:10 pm
by yousmellchinese123
Has anyone seen dry ice at competition yet? o__o
Re: Temperature Task
Posted: March 12th, 2011, 11:10 pm
by Primate
bwy wrote:
Yeah, I'm not sure the whole nichrome/bimetallic strip thing meets the "spirit of the task" either
In which case I don't really see any way of doing this task. They're basically asking for ice cubes or cold packs... to do what?
Why not? It's more than difficult enough to implement.
Thermistors are your other option.
Re: Temperature Task
Posted: March 14th, 2011, 6:30 am
by JTMess
How are you guys keeping the time down on the temperature task so it doesn't take too much time from the sand timer? Our bimetallic strip is taking about 38 seconds to cool, which makes the task not even worth the 50 points compared to the 76 points the sand timer cound earn in this time.
Re: Temperature Task
Posted: March 14th, 2011, 6:09 pm
by Primate
JTMess wrote:How are you guys keeping the time down on the temperature task so it doesn't take too much time from the sand timer? Our bimetallic strip is taking about 38 seconds to cool, which makes the task not even worth the 50 points compared to the 76 points the sand timer cound earn in this time.
Find a different bimetallic strip, or cut it down (width/thickness, not length). Ours takes five seconds.
Re: Temperature Task
Posted: March 21st, 2011, 4:52 pm
by noahb1110
My temperature task is nearly instantaneous, it take like half a second.
Re: Temperature Task
Posted: March 21st, 2011, 5:16 pm
by bwy
noahb1110 wrote:My temperature task is nearly instantaneous, it take like half a second.
Are you going to just drop that hint without telling us what it is?
