Thermistor and the Egg Incubator

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I wrote about making an incubator (Read more on that one here: 1st Chicken Incubator) a while back. It did work for 2 or 3 chicks now (out of probably 16 eggs that went into the bator) however my thermostat died. It was  / is a baseboard digital thermostat, min load 500 watts for what thats worth (I have it running a 60 watt bulb 😛 So much for following specs). Its thermostat innerds are all one chipboard basically which means I had to have the whole thermstat inside the bator. Now with incubators comes humidity, you need to keep the humidity higher in there for the chicks. This was getting into the circuitry of the thermostat and it killed the LCD for example and shorted other part and so my incubator became unstable, actually in some cases it just wouldn’t work. And that isn’t good for incubators, you need constant heat to keep the eggs cooking’! I set out then to find a way to create a thermo probe for it so I could stick the probe in the bator but leave the thermostat as a whole outside so its not affected by humidity and therefore is usable again. This is where I got into learning what a thermistor is. This is the device that actually measures the temperature – or at least reacts to that temperature. Below is the image of a thermistor, one very similar to what i had on mine soldered right to the LCD circuit board. It was about 2 cm long. An unusable length in terms of keeping the thermostat outside the incubator. So, I had to cut the wires and extend it myself with some scrap wire.  These thermistors are sold in different resistances basically to allow for whatever temperature range you’re looking for.

Thermistor - for reacting to temperature change
Thermistor – for reacting to temperature change

Here is from wikipedia which is as always a great source of info:

thermistor is a type of resistor whose resistance varies significantly with temperature, more so than in standard resistors. The word is a portmanteau of thermal and resistor. Thermistors are widely used as inrush current limiters, temperature sensors, self-resetting overcurrent protectors, and self-regulating heating elements. Thermistors differ from resistance temperature detectors (RTD) in that the material used in a thermistor is generally a ceramic or polymer, while RTDs use pure metals. The temperature response is also different; RTDs are useful over larger temperature ranges, while thermistors typically achieve a higher precision within a limited temperature range, typically −90 °C to 130 °C.[1]



I succeeded in my venture, I was able to extend it and make my self  a probe so now I can keep the thermostat outside the incubator, away from the high humidity and now I don’t have to toss away my $7 I spend on that baseboard thermostat 🙂 Currently in progress are about 10 eggs. Hoping to increase my hatchrate this time. Maybe 2 out of the bunch?! Not sure what the trick is to getting 80% hatch rate or something, I’m doing a pretty redneck job of the whole incubation thing but hey… eggs are relatively cheap right now so losing a few isn’t the end of the world. Stay tuned for hatching in about 3 weeks.

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