Re: [DIYbio] Building an incubator, would like some opinions/help

Most non-shaking dry incubators don't even have fans. If you are using it for plates I would in fact advise against fans or major airflow as these tend to dry out the plates in my experience. A temperature controlled incubator can be created with one or two $3.50 thermoelectric peltier devices, TEC127601 is probably good, a temperature sensor, a microcontroller and some kind of insulated box.

Good luck.

On Friday, January 4, 2013 2:22:06 PM UTC-6, Nathan McCorkle wrote:

Ahh, I DID mean 12V not 120V! TYPO! Yeah it's a 'hair dryer' but it's sold for car use, like defrosting ice in the cold morning when the engine isn't warm to blow heat.

I was planning on PWMing the MOSFET on the dryer, I doubt it will overtemp shutdown (the one I bought seems so cheap they probably didn't add that feature) because I'm only keeping the incubator at max 40 C degrees, and it's such a small volume that I the temps will stabilize within a few seconds. 

I also was thinking that my temp ramp rate needs to be slower than my temp+RH sensor can update (by PWM and maybe undervolting the heater), so if I need to add PID control, it would be less likely to overshoot and get into some weird oscillation.

I WAS planning on having the 12V heater and 12V fan IN the incubator, I was just hoping that the fan wouldn't short. I supposed I could add a bit of magnet to a fan blade for an encoder and make sure I see ticks when I turn on the fan.

I should also mention I ordered an opto-isolated 4-relay circuit board to switch the 12V and 120V (the fogger). I also considered using a $25 marine bilge pump fan for swirling the air inside, but I think a quick coating of compressed/canned polyurethane spray would seal a simple fan enough... I would hope the coils in the motor were all insulated anyway (or they wouldn't work as coils I think)

Here's a diagram

http://nathanmccorkle.com/DIY/DIYincubator.png

On Fri, Jan 4, 2013 at 11:46 AM, John Griessen <jo...@industromatic.com> wrote:

On 01/04/2013 02:20 AM, Nathan McCorkle wrote:

So I am thinking of using a glass jar with sterile water and a sonic fogger to add RH.

Adding heat and stirring the air will be accomplished by a 120V 12A hair dryer. I think this MOSFET will work (the volts and amps

are above what I need, but the power dissipation isn't)

You can give that FET short PWM pulses and keep the average power in its range, or
it will burn up.

Hair dryer fans seem fast and noisy for this app.

If you use a wimpy  quiet computer fan and separately PWM control the hair dryer heater,
to slowly swirl air through the hair dryer and incubator, you could recycle the
heated air and it all would be stable.

Hair dryers are not intended to recycle their heated air, and will overtemp shutdown
if you do.

Better be swirling the 120VAC hair dryer air around the jar
and not the humid misted air water through the hair dryer...

I am thinking two dampers (one-way air valves) with a small 100mm computer fan will be sufficient for reducing CO2 levels.

Don't have a picture of that...  relative to the jar == ?

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