Hi,
This is my first "serious" project.
I want to build a coaster, which will measure the temperature of your cup (be it hot tea , cold beer or even fresh hot soup;) ) and notify you when it reaches you favourite value.
You know how it happens, you place fresh cup of tea near your Leptop or TV and because it is too hot to drink right away you want to wait few minutes.
But the internet or movie are so interesting that you compltely forgot about your drink. After you remember it is already too cold. And drinking warm tea or kakao is just disgusting:)
Sometimes there is THE perfect temperature for tea of coffee:)
That is why i want to change to world! Here is my project
I take TI TIM006 for contactless temp sensing,
MSP430F2002 or MSP430F2013 (depending on how much memory i will need) for main control
Another big feature is that the coaster is completely self powered;)
I took TI BQ25504 for energy harvesting purpose which is able to harvest energy down to 50mV input Voltage (after cold start) and charge a capacitor or a battery to 5,5 V!
The two solarcells (52x38 mm) are enough to chage the 1 Farad Supercap.
On my table at common light conditions the charging process is pretty slow, it can take about a whole day to charge from 2V to 3,6V. Under the simple energy saving lamp it is a bit faster and under the direct sun ( near the window) it takes just 10-15 min:)
I have MSP430F2013 running from VCO a simple Timer/Counter in LPM3 and toggling a pin on compare interrupt. The voltage on the storage cap goes down at about 1 mV/minute. So a full charge can power MSP for few hours;) But considering the fact ,that µC will only work when a cup is on the coaster it is more then enough.
Right now i am waiting for SpurkFun TMP006 breakout board, since prototyping with BGA is impossible.
Other features will be:a few touch buttons to control the desired temperature and one Bi-Color(red-blue) or few LED to show the temperature while selection (they will be OFF most of the time). There will be two different temperatures values in MSP memory. One for cold drinks and one for hot. So depeding on initial temperature the msp will know if it is beer or tea;)
The capacitor can be charged to 5,5 V so i am thinking of using TLV7162828P for stepping down the input voltage for MSP43 and TMP006.In this way i can save much more energy (instead of just 4 V which is max. for MSP devices). Moreover the TMP006 works only with 2,2V and MSP from 1,8. So when the Cap voltage drops under 2,2 V it will be still possible to sue the temperature sensor.
In order to turn the coaster on you have to push on it. There will be some kind of pushbutton on the bottom so it will activate the nonmaskable interrupt and start the whole thing.Sometimes it will be enough to place big cup of tea on it, but it wouldnt work with tiny espresso cups:)
The top of the coaster will be made of acrylic glas to allow the solarcells and the TMP006 to function:)
I will be testing the touch buttons using MSP430FG4618/F2013 Experimenter Board soon to see how much power it draws.
I am planning to make a real product of it selling it on tindie.com. The selfcost of the coaster will be around 25 Euros. I am not sure if people will buy it for lets say 50 Euros:)
Hope so:)
Here is what i made so far:
