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Topic: Peltier-based dehumidifying cabinet (Read 2453 times) previous topic - next topic

be80be

Quote
Has a long life, with Mean Time Between Failures (MTBF) exceeding 100,000 hours


I don't see you wearing it out really fast you can lower the voltage or current to maintain temperature. Maybe PWM is not the name to use more like turn it on let it cool a big plate with some mass to it so you end up with real slow cycles. You hit 50 turn it off warms up to 55 turn it back on. 

AdrianLopez

#16
Dec 27, 2012, 10:12 pm Last Edit: Dec 27, 2012, 10:16 pm by AdrianLopez Reason: 1
I've decided to go with capacitively filtered PWM to control the cooler's temperature while switching it on and off altogether to control humidity. So...


  • What's a good place to buy a suitable power supply for the 29.8 VDC, 6A cooler model? This should be able to power both the cooler and one or two 12V computer case fans (using, I presume, a voltage divider for the fans).

  • What kind / spec of relay should I get that would allow me to drive the cooler via PWM at 29.8 VDC and assuming a current of 6A max?

  • What kind / spec of capacitor should I get for the purposes of filtering the PWM signal above?

  • What kind of sensor do I need to tell if water has reached a certain level inside a container?

arduinoPi

Side note: if both of your fans will always be running you can attach them in series and that would make them use 24 volts which is close to your 29 volts.
someone correct me if I am wrong.

AdrianLopez


Side note: if both of your fans will always be running you can attach them in series and that would make them use 24 volts which is close to your 29 volts.
someone correct me if I am wrong.

I'm not sure I want them running 24/7 (thinking about power consumption and wear), but perhaps it doesn't matter?

AdrianLopez

Answering some of my own questions:


  • Mouser carries a large selection of power supplies, so I'll choose one of those.

  • A relay seems to be the wrong choice for use with PWM, but it looks like I could use this MOSFET I found on Sparkfun. Right?

  • For the water sensor, I suppose I could do something like this.



Still hoping for advice on capacitor specs.

AdrianLopez

#20
Dec 28, 2012, 07:07 pm Last Edit: Dec 28, 2012, 07:12 pm by AdrianLopez Reason: 1
No advice on capacitance values needed for a project like this?

Concerning the water level sensor: it turns out the sensor described in the link I posted is subject to corrosion from electrolysis. I've found some circuits (here and here) that turn DC power into AC power on the electrodes in order to prevent corrosion from electrolysis, so those are probably a better choice.

Anyway, thank you all for your help. I may post an update with instructions if I ever get this thing built.

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