Transfer function of a Peltier device

Thread Starter

AmigaBlitter

Joined Jun 7, 2017
2
Hello everyone,

i have to write the transfer function of a peltier module.
I really don't know how to do this.

I'm creating a little system with Arduino, using a temperature sensor Waterproof (DS18B20) and a Peltier module (tec1-12706) controlled with a Mosfet connected to a arduino PWM port.

I need to write a simple transfer function.

Can anyone help me?
 

wayneh

Joined Sep 9, 2010
16,790
For most calculations you can treat the module as a resistor. It'll roughly behave as a 2Ω resistor. I believe at very low voltage it may become non-ohmic. That is, it's a semiconductor and my not conduct below 0.7V or so. If that matters, you'll need to look up the low voltage behavior.

And if you need more precision, you'll have to model how the resistance increases with heat, and understand your system well enough to predict temperature.
 

DC_Kid

Joined Feb 25, 2008
796
does the peltier device have a power factor? most things are not pf=1

and as mentioned in post #2, the load probably changes some operating characteristics as device temp changes, so maybe look and see if thats linear or something else.
 

MrAl

Joined Jun 17, 2014
7,965
Hello everyone,

i have to write the transfer function of a peltier module.
I really don't know how to do this.

I'm creating a little system with Arduino, using a temperature sensor Waterproof (DS18B20) and a Peltier module (tec1-12706) controlled with a Mosfet connected to a arduino PWM port.

I need to write a simple transfer function.

Can anyone help me?
Hi,

You probably need a data sheet or else you have to energize the unit with different currents and measure the changes you need to know.
You can probably measure voltage vs temperature differential, but probably current vs temperature differential is better. It may be nearly linear, or it may not be. Check your data sheet or look at some other data sheets to get an idea what you are dealing with.
If it is a curve then you just have to do a curve fit on the data. That will give you a function like:
dT=f(i)

which for a linear transfer function would be like:
dT=K*i

and a quad fit would be like:
dT=a*i^2+b*i+c

I would be surprised if you need anything more than a quadratic fit.

The best way to handle a control system though is to use feedback not a feed forward technique which it sounds like you are after. The feedback makes constant measurements and adjusts the system control parameter as needed.
 
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