You are correct there - that approach is cheaper.... and Stefan is correct - a person "could" spend $30+ for a temperature controller that would hold the temperature closer to setpoint.... but where is the fun in that? This was a chance to etch a PCB, design a circuit, and do some uC programming. Great fun:)
Had I purchased all the components the cost would surely have been more than buying - but due to the generosity of a friend and my spare parts bin, I think about the only thing purchased for the temperature sensor itself... oh, and the $3 Radio Shack box. I have several of the $4 uC chips laying around and this was a perfect chance to learn some code for the uC.
Ken H>
--- In Homebrew_PCBs@yahoogroups.com, "saposoft" <sapoliste@...> wrote:
>
> There is a cheaper and easier solution than an Arduino and IC temp sensor, if you look back in the archives of the group you can find a few solution for tempo control cheap and easy to DIY.
> mine is located here
> http://sites.google.com/site/elettronicaarduinoesperimenti/Home/thermostat-with-ua-741
> You need a thermometer for the first calibration, but once you do this it will work like a charm, I'm using it for my laminator.
> have fun
> Sapo
>