I am just pushing the success here forwards as a lot of people who just want to measure temperature accurately and siimply with ZERO fuss need to know about this. Give it a spin folks as this is probably the best tthig you could use to demonstrate Cayenne out of the box with just a single 4k7 resistor.
- Virtually one part device.
- Direct Pi Compatible,
- NO interface needed (other than that annoying 4k7 pull up)
- -55 to + 125 Deg C
- Zero callibration or fiddling needed.
- 0.5 Deg C accurate out of the box and 1/16th deg C resolution ( mad ! )
- It works !
Here is how on a breadboard:
- The DS18B20 is a three wire DIGITAL thermometer
- There wre three wires: +ve and a-ve and a single ‘1 wire’ buss that hooks onto the Pi header pin 7 = GPIO-4 1w = one wire point.
- Coolest thing is you can daisy chain multiple DS18B20 with the 3 wires all in parallel and the unique ID and cleverness of Cayenne sorts it all out: Each thhermometer just pop’s up without having to do ANYthing on the Dashboard by the time you can turn back to the screen.
- Wayyyyyy Coollllllllll
Here is screen:
I will be more than happy playing with this for a while but ‘observations’ and tidy up of the way these devices work are as follows for now…
There seems to be no way to edit tag, descriptor or individulaly name each DS18B20
Degree C option on some sort of a settings table please ( in progress ? )
Note a curious ‘feature’ is that ‘Deg C’ seems to come up initially for a minute or so before someone comes and flips it over to politically correct (?) Deg F for you guys… (have a close look at the plot)
Time and date history gadget ( General graphing + history database ? )
Here is an image of a gadget that interacts with php and a clunky old MySQL I use for monitoring pennguin nesting boxes and solar hot water etc type systems
Last tip request for the low level techies is that it should be entirely possible to get the Pi to issue the WPU (Weak Pull Up Current) and thus eliminate the slightly untidy but irritating single 4k7 external resistor. I think that the Pi at the lowest level can have this switched on (minor code tweak in sofware). This would mean full plug and play that for the 90% of simple single digital temperature probe setups. FAB demo, or kitset (you can buy these finished, sealed in high temperature, stainless food grade + 1.5 m lead for ~$2