Good luck to him. I tried this a couple years ago and found it way too noisy to work. Perhaps he'll find a way.

From Hackaday:

[Tim] is getting his drone ready for SparkFun’s 2013 Autonomous Vehicle Competition on June 8th. He has a pretty good start, but was having some problems accurately measuring travel distance. The technique he chose for the task was to glue magnets onto the axles of the vehicle and monitor them with a hall effect sensor. Those sensors are finicky and a few problems during testing prompted him to look at a redundant system. Right now he’s experimenting with adding an optical mouse sensor to the autonomous vehicle.

Recently we saw the same concept used, but it was meant for tracking movement of a full-sized automobile. If it can work in that application it should be perfect here since the vehicle is much closer to the ground and will be used in ideal conditions (flat pavement with clear weather). [Tim] cracked open an old HP mouse he had lying around. Inside he found an Avago ADNS-5020 sensor. After grabbing the datasheet he discovered that it’s simply an I2C device. Above you can see the Arduino Leonardo he used for the first tests.

[Tim] coded functions to monitor the chip, including some interesting ones like measuring how in-focus the surface below the sensor is. This brings up a question, is there limit on how fast the vehicle can travel before the sensor fails to report back accurately?

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Comment by Jason Short on April 3, 2013 at 11:58pm

Hall effects sensors are finicky compared to optical?  Oh dear....

He needs to do a basic calculation of the frame rate vs ground speed to get his answer. But I've also found the sensors are sensitive to specific wavelengths of light which means they need illumination from an LED if they are in the shadow of a car.

I made a 16x16 camera from an avago sensor 8 years ago, so this guy is certainly not breaking new ground here. He should ask around some more forums for example code to get him up and running quick.

Also, the APM has plenty of code and support for optical flow sensors already for him to grab.

Jason

 

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