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Very cool. This is how final projects should be -- we shouldn't just shove the entire prototyping board into whatever we're making. Any clues for how to keep 9

Very cool. This is how final projects should be -- we shouldn't just shove the entire prototyping board into whatever we're making. Any clues for how to keep 9v batteries providing enough juice when they're in the fridge? I'm trying to build a fridge monitor: http://gilgamech.blogspot.com/2013/02/wireless-temp-sensor.html http://gilgamech.blogspot.com/2013/02/wireless-temp-sensor.h...

swamp40 14y ago
Lithium is the way to go for anything < 20°C. (A refrigerator should be around 2°C.) Digikey carries 9V lithium cells.
Eduardo3rd 14y ago
Cool starter project! You could solve this problem in a couple of different ways. The most obvious would be running the circuit off of the fridge power supply directly. I'm not sure how comfortable you would be with re-wiring your fridge though. The potential to start a fire is probably relatively small, but it still exists. Another option would be running a small heater around the battery itself. It shouldn't take very much power to keep a 9v warm enough for minimal losses in a fridge. (http://www.bipowerusa.com/products/bipower-bl9v-u.pdf http://www.bipowerusa.com/products/bipower-bl9v-u.pdf)
- HeyLaughingBoy 14y ago
  Instead of using a heater to warm the battery, much better to find a battery that is rated for the temperatures you need to use it.
  - Eduardo3rd 14y ago
    True, but if someone is going for low cost off the shelf 9 volt batteries it could be a temporary solution. Plus they would learn how to build an electrical heater, which is a useful skill to have for lots of applications.
- stephengillie 14y ago
  I've pondered having the device use the fridge bulb plug for power. But that's only designed to be powered when the door is open. So we can use batteries or capacitors, which is back to problem #1. Or we can tape the door switch to be always-on, but I'm concerned about the power drain. Ultimately, this device would influence refrigerator manufacturers to include this technology in their base models. I'm tired of fiddling with dials to try and figure out if my fridge is at 2C or 5C or -1C. (38F or 42F or 30F). I want fridges to know what their internal temperature is, and what we think it should be. I'm thinking more about ensuring wide adoption through low-cost and low-intrusiveness. Modifying my fridge would make a good Hackaday post, but not such a good Kickstarter project. (Maybe even a fridge/freezer with a barcode scanner and multiple compartments -- give it a database table of appropriate temperature ranges for different foods and let it set the temp in each compartment automatically. It could keep your ice cream from melting and prevent your lettuce from freezing? How about sectional temperature controls, like in car cabins?)
simcop2387 14y ago
I'd consider finding a ribbon cable to run into the fridge for the thermocouple in the fridge. If you find a nice thin one you can avoid having the uC and power inside the fridge eliminating most of those problems. Though this would be a less aesthetically pleasing method. As for your broken arduinos it's possible to program them again most likely with something like the USBtinyisp, at least if you haven't fried the uC itself.
- stephengillie 14y ago
  I've thought of several variations on this idea. The most feasible was to have all of the electronics contained inside a plastic box, and this would stick to the side of the fridge with magnets. I'd run a tiny 3-wire cable to the temp sensor, which would sit inside the fridge. It's not the most elegant solution, which is what I'm chasing. I'll look into reprogramming them, but assuming the Arduino prototyping board is ok, I'm only replacing the ~$5 ATMega processors.

swamp40 14y ago

Lithium is the way to go for anything < 20°C. (A refrigerator should be around 2°C.) Digikey carries 9V lithium cells.

Eduardo3rd 14y ago

Cool starter project! You could solve this problem in a couple of different ways. The most obvious would be running the circuit off of the fridge power supply directly. I'm not sure how comfortable you would be with re-wiring your fridge though. The potential to start a fire is probably relatively small, but it still exists. Another option would be running a small heater around the battery itself. It shouldn't take very much power to keep a 9v warm enough for minimal losses in a fridge. (http://www.bipowerusa.com/products/bipower-bl9v-u.pdf http://www.bipowerusa.com/products/bipower-bl9v-u.pdf)

HeyLaughingBoy 14y ago
Instead of using a heater to warm the battery, much better to find a battery that is rated for the temperatures you need to use it.
- Eduardo3rd 14y ago
  True, but if someone is going for low cost off the shelf 9 volt batteries it could be a temporary solution. Plus they would learn how to build an electrical heater, which is a useful skill to have for lots of applications.
stephengillie 14y ago
I've pondered having the device use the fridge bulb plug for power. But that's only designed to be powered when the door is open. So we can use batteries or capacitors, which is back to problem #1. Or we can tape the door switch to be always-on, but I'm concerned about the power drain. Ultimately, this device would influence refrigerator manufacturers to include this technology in their base models. I'm tired of fiddling with dials to try and figure out if my fridge is at 2C or 5C or -1C. (38F or 42F or 30F). I want fridges to know what their internal temperature is, and what we think it should be. I'm thinking more about ensuring wide adoption through low-cost and low-intrusiveness. Modifying my fridge would make a good Hackaday post, but not such a good Kickstarter project. (Maybe even a fridge/freezer with a barcode scanner and multiple compartments -- give it a database table of appropriate temperature ranges for different foods and let it set the temp in each compartment automatically. It could keep your ice cream from melting and prevent your lettuce from freezing? How about sectional temperature controls, like in car cabins?)

simcop2387 14y ago

I'd consider finding a ribbon cable to run into the fridge for the thermocouple in the fridge. If you find a nice thin one you can avoid having the uC and power inside the fridge eliminating most of those problems. Though this would be a less aesthetically pleasing method. As for your broken arduinos it's possible to program them again most likely with something like the USBtinyisp, at least if you haven't fried the uC itself.

stephengillie 14y ago
I've thought of several variations on this idea. The most feasible was to have all of the electronics contained inside a plastic box, and this would stick to the side of the fridge with magnets. I'd run a tiny 3-wire cable to the temp sensor, which would sit inside the fridge. It's not the most elegant solution, which is what I'm chasing. I'll look into reprogramming them, but assuming the Arduino prototyping board is ok, I'm only replacing the ~$5 ATMega processors.