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Case design with internal antenna
11/20/2022 at 08:19 • 0 commentsAs this is supposed to spend most of its time on a pet's collar, I tried a different case design that's flatter and longer. The goal is to get something smaller than the Tractive. So far no effort has been put into details like actually attaching it to a collar or a charging port.
Size is: 76mm x 29mm x 17mm, 34g. That's 3" x 1.2" x 0.7", 1.2 oz
Tractive is 71mm x 28mm x 17mm, 35g. That's 2.8" x 1.1" x 0.7", ~1.2 oz
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Quick battery test with GPS on
11/19/2022 at 08:02 • 0 commentsI ran a battery capacity test. System was configured to stay in sleep and wake up every 10 minutes. Then try to get a GPS fix and transmit an uplink. Then tested this in two scenarios, shown in the following plot.
On the left, a GPS fix is easily obtained and power draw is small. For the middle section the GPS cannot get a fix and it keeps trying for 10 minutes. During this phase 62% of the battery capacity is lost in 8.7 hours.
But something does not add up. With this power profile I expect 14h of run time. Further tests needed. Possible causes:
- Lower than advertised battery capacity at 0.1C discharge rate
- I'm measuring battery voltage wrong
- I'm using a voltage-to-charge LUT that's not appropriate for the battery
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Quick case design
11/18/2022 at 06:21 • 0 commentsFor easier field testing with the small battery I printed a very basic case. This also allows me to get the first real measurement for the total weight of the device.
30 grams is 1.06 ounces.
Weights of other LoRaWAN GPS trackers
RAK Wireless TrackIt: 22 grams
ioTracker 3: 35 grams
Dragino TrackerD: 58 grams
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Battery and antenna
11/17/2022 at 05:06 • 0 comments -
Current consumption
11/16/2022 at 06:46 • 0 commentsAdding up the maximum currents for the components for each state I got:
- Sleep: ~20uA
- GPS on: 34mA
- Tx: 45mA
- Rx: 15mA
On measurement things improve a little:
- Sleep: ~9uA
- GPS on: 35mA
- Tx: 33mA
- Rx: 14mA
Using a 400mAh battery, keeping the GPS off and sending one uplink every 15 minutes should give ~130 days of battery life on 80% of the battery charge.
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First tests with Helium
11/15/2022 at 05:52 • 0 commentsWhile waiting for proper batteries and antennas I put something together and threw it in my backpack. As there are not many The Things Network gateways in Bucharest, I used Helium for this test. There is excellent Helium coverage and the Quectel L80 module got a lock in the car, on buses, trams, even on the couch in my living room.