There should be sufficient resources attached here to build the cooling controller.
Some pix - the board layout, another 3D image, a BOM (Bill of Materials) csv file and pcb layout to scale in the zip file (document viewer or pdf for the pcb)
Need the usual array of tools and chemicals to make a single sided PCB.
It really needs a visual indicating system of some sort. I will look at using an LED to illuminate at set point. As mentioned a voltmeter will do.
Set temperature in mV by turning POT1 with a voltmeter across R6. To measure actual temperature move the voltmeter positive probe (the Red one) to pin 2 of 750R. These points are connected to the - and + pins of the OPAMP and analog ground.
The supply voltage is much more stable with the use of a Zener diode as opposed to another potentiometer. It means that the voltage to the reference input varies slightly with different voltages but this is transparent to the operator. In any case the supply should not drop below that for the opamp and the temperature sensor - 3 and 2.7volts respectively.
The 0 resistor module is actually a wire jumper!!!
A word about the mosfet - this part is most likely not available at Jaycar. The very low rds(on) spec is essential otherwise a heatsink is required. These mosfets run cold in your hand and work at very low gate voltages. But keep in mind that resistance and therefore heat increases with lower gate voltage. Usually 10V is the spec - if running at 5V drain resistance will increase marginally - but still remain cool.
Through hole T220 packages that fit the bill - check prices (RS Components vs Digikey vs Mouser vs UTSource, etc etc)
NXP PSMN1R1-30PL
IRL40B209
I have tested this primarily at 8v - input will depend on the rating of the TEC. I said 3 - 15 previously - 5 - 6v minimum is more practical, as this will power the smaller TECs very efficiently.