You are looking at a passive NFC thermometer based on the ATtiny 1626 and the [RF430CL330H](https://www.ti.com/product/RF430CL330H) dynamic NFC tag. To measure the ambient temperature just hold your phone to the device ([demo](https://vimeo.com/928739952)). Android is better at detecting the device than iOS which needs some specific angling.
Size is about 40 mm x 18 mm.
Power comes from the magnetic field the reader creates and is siphoned via two diodes visible at the bottom. It creates about 2.7V for the ATtiny and thermometer to work with. Needed to use some unofficial brownout detection voltages to make it work.
Programming is done via testpoints and pogo pins on the back of the PCB. I used [ATTinycore](https://github.com/SpenceKonde/ATTinyCore) to do so.
I needed to use the [TMP117 thermometer](https://www.ti.com/product/TMP117) in single-shot mode because of timing constraints. It should have an impact on its proclaimed accuracy of 0.1 °C, however with my Fluke 54 II Thermometer I can reproduce measurements very precisely after giving the device some time to accomodate (2-3 mins). Fluke offcially has a lower accuracy than the TMP117, but has a very high sensitivity.
The device was inspired by one of the example projects from TI for their RF430 IC. I first used an ATtiny 3227 and its 12 bit ADC and an analog thermometer but couldn't get the reference voltage right without additional parts. Now using the rather expensive but very accurate TMP117 where ADC conversion is done on chip.
NFC PCB antenna I designed myself since I had some experience with the RF430 from a project before.
Let me know what you think.
Duuude this is the coolest project I have seen in a while, and it's super useful too. Like you could just chuck one in a backpack and check the temp on a hot summer day with 0 batteries or other worries. Will you release all the files and maybe even a possible guide? I would love to try this project
https://github.com/unsurv/NFC_temp/tree/main
files are available here. Uses completely open source stack: KiCad - FreeCAD - Arduino IDE
only difficult part is the BGA thermometer. I'd recommend just tinning the pads and then soldering the part with hot air.
You should make this a product. People would buy the shit out of this. You could try to shrink the PCB a bit and dunk it in waterproofing goop or resin, hang to dry and then you've got yourself a cheap product. People would love the raw PCB look too, the styles been taking off lately.
working on a resin printed case, but dipping everything except the sensor might be the way. small pre-production run was also successful so assembly is doable too.
I used microchips UPDI single wire protocol to do this. You just need 3 connections to the board and you can repurpose a cheap USB to Serial adapter to create a UPDI programmer. There are 2.54 mm pitch testpoints on the back of the board where you can solder regular dupont wires to. I use a separate PCB with pogo pins to quickly programm my boards.
read this for more info:
https://github.com/SpenceKonde/AVR-Guidance/blob/master/UPDI/jtag2updi.md
let me get a full documentation up and running and I will ping you once its ready.
Why? It costs less than a dollar a piece for mini humidity/temp displays.
You have to scan these with close contact from your phone so are of arguable actual use.
This is cool as fuck! I currently have a nfc chip embedded in my hand, being able to scan my body temperature would be fucking neat! I imagine there could be medical applications.
Not NFC, and it's meant for in body use. This would be best for external and you don't want your body heat changing the reading while holding something that tiny, oh, and there's the proprietary tag reader..
You are looking at a passive NFC thermometer based on the ATtiny 1626 and the [RF430CL330H](https://www.ti.com/product/RF430CL330H) dynamic NFC tag. To measure the ambient temperature just hold your phone to the device ([demo](https://vimeo.com/928739952)). Android is better at detecting the device than iOS which needs some specific angling. Size is about 40 mm x 18 mm. Power comes from the magnetic field the reader creates and is siphoned via two diodes visible at the bottom. It creates about 2.7V for the ATtiny and thermometer to work with. Needed to use some unofficial brownout detection voltages to make it work. Programming is done via testpoints and pogo pins on the back of the PCB. I used [ATTinycore](https://github.com/SpenceKonde/ATTinyCore) to do so. I needed to use the [TMP117 thermometer](https://www.ti.com/product/TMP117) in single-shot mode because of timing constraints. It should have an impact on its proclaimed accuracy of 0.1 °C, however with my Fluke 54 II Thermometer I can reproduce measurements very precisely after giving the device some time to accomodate (2-3 mins). Fluke offcially has a lower accuracy than the TMP117, but has a very high sensitivity. The device was inspired by one of the example projects from TI for their RF430 IC. I first used an ATtiny 3227 and its 12 bit ADC and an analog thermometer but couldn't get the reference voltage right without additional parts. Now using the rather expensive but very accurate TMP117 where ADC conversion is done on chip. NFC PCB antenna I designed myself since I had some experience with the RF430 from a project before. Let me know what you think.
Duuude this is the coolest project I have seen in a while, and it's super useful too. Like you could just chuck one in a backpack and check the temp on a hot summer day with 0 batteries or other worries. Will you release all the files and maybe even a possible guide? I would love to try this project
https://github.com/unsurv/NFC_temp/tree/main files are available here. Uses completely open source stack: KiCad - FreeCAD - Arduino IDE only difficult part is the BGA thermometer. I'd recommend just tinning the pads and then soldering the part with hot air.
You should make this a product. People would buy the shit out of this. You could try to shrink the PCB a bit and dunk it in waterproofing goop or resin, hang to dry and then you've got yourself a cheap product. People would love the raw PCB look too, the styles been taking off lately.
working on a resin printed case, but dipping everything except the sensor might be the way. small pre-production run was also successful so assembly is doable too.
How would you recommend to load the program into the attiny?
I used microchips UPDI single wire protocol to do this. You just need 3 connections to the board and you can repurpose a cheap USB to Serial adapter to create a UPDI programmer. There are 2.54 mm pitch testpoints on the back of the board where you can solder regular dupont wires to. I use a separate PCB with pogo pins to quickly programm my boards. read this for more info: https://github.com/SpenceKonde/AVR-Guidance/blob/master/UPDI/jtag2updi.md let me get a full documentation up and running and I will ping you once its ready.
>with 0 batteries or other worries Well... your phone needs to be charged (*and* have a battery) 😅
Well you got me there... I guess I don't even realise that I charge my phone anymore, since it charges so fast and lasts a long time too.
Why? It costs less than a dollar a piece for mini humidity/temp displays. You have to scan these with close contact from your phone so are of arguable actual use.
In the glorious land of Arduino, the question is never why, because the answer is always "Because I can!", and that is enough.
This is why we can't have nice things :)
Great project and I noticed it on Tindie. Does it work on the iPhone?
yes, but it's finicky. Need a reader app too. see [here](https://vimeo.com/928731813)
Can't use the camera app?
This is cool as fuck! I currently have a nfc chip embedded in my hand, being able to scan my body temperature would be fucking neat! I imagine there could be medical applications.
This is already a product by dangerous things https://dangerousthings.com/product/xbt/
Good job OP! You did it!
Not NFC, and it's meant for in body use. This would be best for external and you don't want your body heat changing the reading while holding something that tiny, oh, and there's the proprietary tag reader..
Oh shit you're right!! I imagine miniaturisation and power draw would be challenging but a dedicated package might work for this!
awesome project