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Exploring use of Peltier elements

A project log for ADITI:Affordable Diagnostic Thermal Incubator

Aditi is a connected bodysuit heating enabled incubator for preterm infants measuring Heart Rate, SpO2,Temp & Respiration comfortably.

manoj-kumarManoj kumar 10/10/2016 at 06:150 Comments

One other alternative I had to textile based warmers was the use of a thermoelectric module(Or Peltier element). A typical thermoelectric (TE) module is composed of two ceramic substrates sandwiching many pairs, or "couples" of Bismuth Telluride dice. The (pairs of) dice are connected electrically in series, and thermally in parallel, between the ceramics. One of these ceramics will be the "hot-side" and the other, the "cold-side."


(Credits: Advanced Thermoelectrics)

While both P-type and N-type materials are alloys of Bismuth and Tellurium, both have different free electron densities at the same temperature. P-type dice are composed of material having a deficiency of electrons while N-type has an excess of electrons. As current (Amperage) flows up and down through the module it attempts to establish a new equilibrium within the materials. The current treats the P-type material as a hot junction needing to be cooled and the N-type as a cold junction needing to be heated. Since the material is actually at the same temperature, the result is that the hot-side becomes hotter while the cold-side becomes colder. The direction of the current will determine if a particular die will cool down or heat up. In short, reversing the polarity will switch the hot and cold sides.

These modules are extremely efficient in heating/cooling application of about 70% and have extremely long cycles of operation.
Let's now look at a peltier element


Here is the base temperature of the peltier element


Temperature is in Celcius for those of you in the USA,
Now I'll set my power supply at 5V



The Thermoelectric module instantly heats up instantly, No Ohm's law here all solid state up here.

It get's pretty toasty, Definitely needs some PWM to control the temperature between some safe limit. In comparison the Litex fabric consumes over 700mA of current at 5V for roughly the same temperature and it takes over 2 minutes to heat up.

We were blown away by the performance of the Peltier element and we plan to use it along side the Litex fabric in our future revisions.


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