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Support Forum » Overheated Temperature Sensor

June 19, 2009
by Ethanal
Ethanal's Avatar

While experimenting with my temperature sensor, it got very hot, like it was shorted or something, and now it doesn't take accurate readings. Where can I get a replacement?

June 20, 2009
by mrobbins
(NerdKits Staff)

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Hi Ethanal,

You can order replacements from us directly. Just send us an e-mail at support email address and let us know what you want (this and any other parts).

In my experience, the surest way to damage these parts is to switch the power and ground leads, which causes the chip to get very hot due to undesired direct conduction, and may or may not cause permanent damage. Can you verify the orientation of the power/ground leads of the sensor?

Mike

July 01, 2009
by Ethanal
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Yes, I made sure it was in the breadboard correctly and it still reads the temperature roughly 10 degrees above the real temperature. I will order a new one soon.

P.S. Can we get things like multiplexors or other common I.C.s from you guys too?

July 01, 2009
by mrobbins
(NerdKits Staff)

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Hmm... is it possible that the battery is low? If you have a multimeter, check that your +5V output of the 7805 is really 5.0 volts. If it's low, the temperature reading will appear high because the math is based on the full scale being 5 volts. Also, if you have a multimeter, measure the voltage output of the LM34 directly. This should be 10mV per degree Fahrenheit, so if it's 72 degrees, you should see about 0.720 volts.

We don't have other ICs available yet... what kind of multiplexers and other parts would you want? I think we can make that available soon. Let me know!

Mike

July 07, 2009
by Ethanal
Ethanal's Avatar

I never thought about that... I just changed the battery a few days ago, but haven't tried the temperature sensor project again. That's most likely the problem.

About the multiplexer, I don't really know what kind of multiplexers are best for different situations, but I wanted to make a more compact version of the LED marquee with less risk of wires shorting/falling out.

For the ic's, I was thinking about using a real time clock in a project in the future. Also, what is a hex/octal buffer? They seem to pop up a lot in circuits, but I can't figure out what they are for.

Thanks

July 08, 2009
by mrobbins
(NerdKits Staff)

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Hi Ethanal,

A "buffer" is just a digital device that takes a digital input and has the same output, bit for bit. This doesn't sound like it's doing anything, but it can help drive larger loads (more current), or reject analog noise that has been added by restoring a signal to its strongly high or strongly low voltage level (digital 1 or 0).

When you see "hex" it just means 6 buffers in one chip package, and "octal" means 8 buffers in one chip package. Hope that helps!

Mike

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