I have the cheap version PCR machine completed, so here is the new parts list:
|2x 0.4C Temp sensors||LMT86QDCKTQ1||$0.60|
|2x 11W 10ohm heating resistors||SBCHE1110RJ||$0.78|
|2x 4A N-Mosfets||TSM2310CX||$0.80|
|Capacitors and Resistors||various||$0.50|
|aluminium extrusion||as described||$0.50|
|12MHZ crystal||XTAL003210- HC49/4HSMX||$0.27|
|USB mini connector||$0.45|
|Custom 2-layer PCB|
purchased in bulk
The parts are commonly available and prices are good estimates for buying at single quantities You will just need a 9V 3A power supply to complete the project. That's a sum total of just $7.32, if you are buying single parts.
Moving to an ATTINY design would save about a dollar, and hand soldering on a 5x7cm perfboard a further 40 cents, lowering the cost to about $5.92, which I'll hope you will allow me to round down to the target price of $5 :) However, sticking with a custom PCB and buying a batch to make 100+ PCR machines, the price starts approaching $4.