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E coli incubator Answered

I am building an incubator for ecoli.  Any comments or improvements?

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avocadostains (author)2017-12-07

It looks like it is arduino controlled, which is awesome, but beyond my understanding, so I can't help you there.

Is the incubator built yet? What are the temperature/light/humidity requirements of E. coli. Is it something where a simple temperature switch wired to a light bulb would be good enough? https://www.ebay.com/itm/2Pcs-10A-250V-KSD301-30-C... (Such as those) Also there are good DIY Sous Vide instructables that would provide more precise temp control, depending on which controller you buy, you can also control humidity levels. I'm sure you can do all that with Arduino too, but I wouldn't know where to start.

Also, I just kind of took a leap of faith and assumed you weren't a bioterrorist or something? Why exactly are you culturing E.coli? I had that before. It was gnarly, bloody diarhhea for 2 weeks or so.

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drystreams (author)avocadostains2017-12-08

Im not familiar with the temp switch and what ranges activate them. Ecoli incubation requires the ecoli to incubate at 35 degrees celcius (-+0.5). I take water quality samples to determine the health of streams. Thought it would be fun to build a cheap incubator.

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avocadostains (author)drystreams2017-12-08

Those temp switches, and I believe all bi-metallic temp switches are rated as accurate to about (-+2 degrees Celsius) . They are very precise. The problem that leads to that 2 degree or more swing lies with the controller and the heat source. The controllers are usually only programmable by integer degrees. So if you set an incubator set for 35C, the heat wouldn't kick on until the temperature dropped to 34C and it wouldn't kick off until 36C. Then, residual heat from your heat source can make the temperature rise even higher. To combat this, pick a heat source of appropriate wattage to the space you are trying to heat. Ideally you want the heat source to remain on as close to 100% of the time as possible. Shutting on and off contributes to the swing in temperature.

If arduino allows for fractional degree programming, like if you could set the value to 35.4C or 35.425C, I would be VERY interested to know. It may even make me consider learning arduino:) Hope this helps.

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drystreams (author)avocadostains2017-12-08

unfortunately +-2 degrees does not work.

I have it set for 34.9 degrees. When it kicks off, the heat sink allows the temp to climb to 35.2. when it cools down, the temp gets down to 34.7 (even though it kicks back on at 34.9). It is staying within the range I need. its a 100W 12VDC heater (large resistor). Its been working well for 4 days now.

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avocadostains (author)drystreams2017-12-08

Wow! That is impressive temp control. Definitely makes me want to learn more about arduino.

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drystreams (author)avocadostains2017-12-08

Arduino is pretty cool! Can do lots of stuff and there is a lot of code, tutorials and help in open source. Give it a shot!

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user

Nevermind. I just saw my answer. For water quality samples. Good enough for me. You're clear to fly.

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drystreams (author)2017-12-07

The blue wire is the input to switch from NO to NC. But I see your point...just turning on the relay will do the job. I have had no issues with power (been running 3 days) but will incorporate capacitor. Curious if I needed any relays.

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drystreams (author)2017-12-07

make better pets than chickens...

For water quality samples.

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rickharris (author)2017-12-07

WHY? Most people avoid Ecoli.

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drystreams (author)2017-12-07

specifically do I need any resistors other than the one for the DHT22?

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drystreams (author)2017-12-07