This project is effectively a "group buy" on an AD8495 breakout board. The AD8495 is a K type thermocouple amplifier chip. In a nutshell, you connect up a K type thermocouple to the input terminal block and plug the three pin header into your breadboard. One pin is ground, one pin is a 3-30 VDC power supply, and the third pin will output a voltage of 5 mV per degree Celsius from the thermocouple. This is ideal for feeding into, say, an analog pin on an Arduino. To build my own DIY reflow oven, I needed an analog output thermocouple amplifier. The idea behind this project is to make that easier for the next fellow who comes along. The circuit is the reference design straight from the data sheet:
There are alternatives to this project - there are breakout boards for thermocouple amplifiers available from SparkFun, but they're all for SPI devices. In my project, I was unable to use them, because I was using an ATTiny85 and the USI bus was already dedicated to i2c. I did, however, have a single analog input pin - ideal for an analog temperature system. Since I was going to deal with a temperature range of roughly 0-300 degrees Celsius, I needed to use a thermocouple (nothing else would go so high). I wound up using an AD595, but that chip is very expensive. This project aims to provide a solution at less than half the cost.
I propose to build 1000 breakout boards. The BOM at that quantity, plus my time to put them together winds up being about $5 each, which is the "reward" level for this project.
The PCB design is up at OSH Park:
When the project is funded, I will buy the parts from DigiKey and assemble them myself. I plan to use reflow soldering techniques with the oven that inspired this project.
Ordering the circuit boards will take approximately two weeks. Ordering the parts will take place concurrently. I will provide updates as the parts and boards are ordered and as they arrive.
Even though the boards will be reflowed a dozen or two at a time, parts placement is still going to be a manual process. I have a day job, so in the evenings, I anticipate being able to churn out 10-20 boards, and on the weekend probably another 50 or so. At that rate, the full run of 1000 would take between 10 weeks and two months.
Risks and challenges
This project is very simple, straightforward, and basically "fail proof."
The only obstacle to fulfilling this project is if the funding fails, or if lightning strikes me and makes me physically unable somehow to assemble the boards.Learn about accountability on Kickstarter
- (30 days)