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the.Legend

Prototype GPS Speedometer DYI for around 35$

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A quick project for tracking basic data during flight. This is a garage project I made out of own curiosity. Not tested in flight yet, if you decide to do it you're doing it at your own risk.

There are advanced solutions on the market like Dekunu One or Aon X2 and if you can afford them I encourage you to use professionally made equipment.

 

You'd need:

* Car GPS speedometer (I used this one because its shape and size are already almost snag-free: https://www.aliexpress.com/item/4000265066382.html

* Powerbank (with least capacity and smallest size possible - in the prototype this one was used: https://www.aliexpress.com/item/32945597181.html )

* 850 mAh battery (ideally 2000 mAh, but unlikely they'll fit inside the case)

* Small switch

 

Assembly is pretty straightforward: unsolder USB ports on both GPS and powerbank, solder switch and battery. Additionally I flipped the capacitor (it's under white tape on the first photo) - put it on the opposite site of the board to give some room for powerbank's charger.

The device is mounted on a rig using velcro strap with a loop.

 

So far I tested it on the ground on a bike and the speed is pretty accurate - +/- 1 km/h to what smartphone GPS shows

Even with 850 mAh battery the device help up for around 8-10 hours (screen constantly on) which is quite impressed actually.

Talking about the battery - attentive reader might notice that it got swollen - probably because powerbank's changer is for 2000 mAh, while battery is 850 mAh. That's a critical flaw because swollen battery has high risk of explosion as pressure changes during climb to the altitude. If I ever decide to use it for actual tests, the batteries will be replaced with non-chargeable lithium batteries just like in audibles (powerbank's module would still nicely convert that into a constant 5V supply). Meanwhile I'm doing some more research to find safe chargeable batteries.

 

Now, what this thing can do:

* Display current ground speed (both metric and those other, inferior units). Speed alarm can be set at as high as 200 km/h, so I'd assume device can measure at lease that much

* Display one of 8 directions ( N/NE/E/SE and so on) - yeah, it's pretty basic, but better than nothing

* Display distance covered, accuracy 100m

* Display few other stats, but those are useless for WS flying

* Oh, yeah, you can change colors :D

 

Again, this is a garage project. I'm only sharing the fruits of my curiosity and taking no responsibility for what you might do with it.

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