missing cats - help needed to design cat tracker

[dougy83]

This one is only $269, 30grams, 45 x 35mm, **broken link removed** I assume there are others having similar or better price and performance. The battery life is pitiful unfortunately.

It shouldn't be particularly difficult to make one containing:
battery: 500mA.Hr LiIon
charger: http://au.element14.com/microchip/mcp73831t-2dci-ot/ic-battery-management-tsop-5pin/dp/1836683
GPS: http://www.sparkfun.com/products/10890
GSM: http://www.sparkfun.com/products/10138
low power microcontroller
3v3 regulator

The above should be able to run for around 4 days assuming 40mA x 35seconds for each of the GSM and GPS modules. You can attach an nRF24L01+ or similar to detect the cat within ~50m of your house to allow for GSM and GPS to be disabled and reduce power consumption to roughly zero during this time. All devices only require a serial connection and simple commands. It's just over $100 in parts.. but would require a bit of effort to glue together

 

[kubeek]

Account for battery cost (around $15-20), antenna for the gsm module, microcontroller, pcb, and case, and you're getting pretty close to the market price of that trakapet device, and not even close to it's size i'd say.

 

[dougy83]

Account for battery cost (around $15-20), antenna for the gsm module, microcontroller, pcb, and case, and you're getting pretty close to the market price of that trakapet device, and not even close to it's size i'd say.

BL-4C 890mA.Hr is $3.30 incl. international postage. There's likely to be smaller, cheaper models available.
GSM/GPRS module including antenna $24 incl. international postage. **broken link removed**
The Wavecom module can be programmed to likely remove the need for any extra microcontroller whatsoever.

 

[kubeek]

Still about the same size as the trakapet, but probably thicker. I am not saing it can't be done cheaper, but these are just modules which are far from a marketable product. The cost of development might be too much if the demand for such devices is low.

 

[Mr RB]

...
The above should be able to run for around 4 days assuming 40mA x 35seconds for each of the GSM and GPS modules. You can attach an nRF24L01+ or similar to detect the cat within ~50m of your house to allow for GSM and GPS to be disabled and reduce power consumption to roughly zero during this time.
...

If the collar has GPS it doesn't really need local detection. I would just power up the GPS every 20 minutes or so and check the GPS coords are still local. If not, then it goes into "kitty run away" mode and starts transmitting the GPS coords back to the user's cellphone by SMS.

So by my count it only needs GPS and SMS capability, and micro and battery of course.

You could even add a temperature sensor to detect the cat's body heat showing it is alive and well. So if that reads ambient the collar can transmit a second message "kitty run away and is now dead".

 

[dougy83]

If the collar has GPS it doesn't really need local detection. I would just power up the GPS every 20 minutes or so and check the GPS coords are still local. If not, then it goes into "kitty run away" mode and starts transmitting the GPS coords back to the user's cellphone by SMS.

The local detection means you can use a ~24uA average current drain (1Hz message rate, 2ms @ 12mA) rather than the 2.3mA average for checking GPS (10min period, 35 seconds @ 40mA) [half that if 20min period].

Granted it is extra bulk and another nRF24L01+ unit(s) will be required at the house -- for max battery life benefit either another GSM module or PC/internet connection is required - meaning the cat GPS & GSM never needs to be fired up -- but for cats that hang around the yard it will increase the baseline battery life to ~2 years.

 

[large_ghostman]

i dont know the link i will ask dad but we had a bull a big exspensive one that had a small chip clipped to its ear so if it was stolen they could call a company and they found it by a map on the net, it was some kind of GPS thing very very small but very £££££. then again the bull was worth a huge amount! untill it got TB and had to be shot .

 

[IntelGent]

I'm fairly certain this is easily small and light enough for a cat to wear.....

**broken link removed**

 

[tcmtech]

No need to design any further I found everyones missing cats.

They are at my house because my wife is feeding them.

You can have yours back or pick a better one if you want. I wont tell.

 

[Mr RB]

The local detection means you can use a ~24uA average current drain (1Hz message rate, 2ms @ 12mA) rather than the 2.3mA average for checking GPS (10min period, 35 seconds @ 40mA) [half that if 20min period].

Granted it is extra bulk and another nRF24L01+ unit(s) will be required at the house -- for max battery life benefit either another GSM module or PC/internet connection is required - meaning the cat GPS & GSM never needs to be fired up -- but for cats that hang around the yard it will increase the baseline battery life to ~2 years.

Thanks Dougy I missed that. It might well be worth the extra base unit and extra module in the collar to get such good energy savings.

 

[dougy83]

i dont know the link i will ask dad but we had a bull a big exspensive one that had a small chip clipped to its ear so if it was stolen they could call a company and they found it by a map on the net, it was some kind of GPS thing very very small but very £££££. then again the bull was worth a huge amount! untill it got TB and had to be shot .

Small ear tags for cattle are generally passive RFID tags. If it has GPS and a transmitter it will need a power source, which will invariably increase its size.

In Australia (and likely other countries), all cattle is required to be tagged (with passive tags) to track their movements between yards, ownership, medication, slaughter or disposal. If the animal has been sold (and the ear tag remains intact), then the national authority will have to means to identify the last reported location of the animal.

@Mr RB, maybe with the basestation as an optional extra due to the increase in cost.

 

[Mr RB]

Yeah, I have trouble seeing this device as economically viable. With existing technology to get it that small would take development resources of a large company and battery life would still be poor enough to be annoying.

Charging battery is another hassle, as the collar would have to be removed from the cat while charging every week (bad) or a swappable battery (bad, because it makes the product much larger with clip on covers, potential waterproofing etc).

And product cost would be quite high, for a product much bigger than a cat would like, and needs charging/battery changing much more often than a human would like.

Personally I just train the cat to come in response to a call, they have excellent hearing.

 

[dr pepper]

If the device was micropower you could charge the battery using a system similar to the kinetic system used in watches, it'll be a while yet though before thats doable.