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Three very-low-current analog ICs make a USB-powered thermostat

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Jerry.Brittingham
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re: Three very-low-current analog ICs make a USB-powered thermostat
Jerry.Brittingham   4/4/2012 8:29:23 AM
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Nicely done. I suspect that anyplace that you might have a USB port would have an ambient well below 60C.

vrheaume
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re: Three very-low-current analog ICs make a USB-powered thermostat
vrheaume   3/27/2012 5:16:10 PM
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A few comments, if I may: 1) If the goal is to create a solution with the smallest number of parts (as the title suggests), it seems like a waste to have a VREF chip just for powering the opamp (why not find/use a 5V-compatible opamp?); it would be nice to have the design choices justified. Myself, I'd try using one of the vref+opamp+comparator combo chips like the LTC1541, LM432 (or others), for a single-chip solution (plus the LM35, of course). 2) It seems precarious to me to actuate a load (the 5V/200mA BLDC fan) with just a 0.1C/1mV hysteresis (referred to the sensor). 3) Be careful when using subjective qualifiers. I think referring to 60C as "the hottest temperature achieved on earth" should be MAJORLY avoided! (taken out of context, this sentence and the graph are slightly ridiculous) Keep the design ideas coming though, it is always fun to read them.

agk
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re: Three very-low-current analog ICs make a USB-powered thermostat
agk   3/26/2012 9:58:35 AM
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A nice and simple circuit with the internal reference of 1.252 volts from TS9001 chip. The author has designed it to on a fan when the temperature raises above 26.4 C and off the same below 26.3 C. A 0.1 deg hysteresis.

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