The summer may have come to a close here in the USA, but any time of the year is a good time for grilling. In the colder weather, it’s a drag to have to stay near the hot grill to keep an eye on your burgers and franks. [Eric Ely] thought it would be smarter to have a meat thermometer that sent his phone the current reading via Bluetooth.
Instead of starting from scratch, [Eric] took an off the shelf electronic thermometer and removed its temperature probe (which was a thermistor). The hardware used an off the shelf Bluetooth board with a companion battery board and prototype board. If you can’t bear to cut up a good thermometer, you can get replacement probes that ought to work just as well.
In addition to the boards and the scavenged thermistor, [Eric] used a couple of resistors. One resistor is in parallel with the thermistor to improve the linearity of the device’s response curve. The second resistor forms a voltage divider that the Bluetooth board reads.
The software (using Node.js and C) is available on Github. The C program reads the temperature and pushes it out using JSON. Node.js provides a server that [Eric] can hit with his phone’s Web browser.
Sure, you can buy wireless thermometers, but what self-respecting hacker wants to carry around a store-bought box just to display meat temperature? Viewing it on your phone has much more street cred. Of course, a real hacker isn’t going to cook on a conventional grill, either.