Author Topic: Fixing a toy drone  (Read 345 times)

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Offline jdraughn

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Fixing a toy drone
« on: July 03, 2018, 01:49:27 pm »
I actually was able to fix it by going through the calibration procedure on page 5 of the manual
Boy am I embarrassed, another RTFM thing.  So please disregard what I posted.

Hi, someone has asked me to take a look at children's toy drone and wanted to get some thoughts on what the problem probably is. When the throttle is at 0, nothing turns (which is intended behavior), but as soon as you start giving it a tiny bit of throttle, two of the blades which turn counter to each other start running at what appears to be 100% on while the other two turn very slowly, which is appears to be caused by the air generated by the other two props.  The two props which go to 100% are the front two props and cause the entire drone to want to move backwards. If I give it 100% full foward stick (right stick forward), which should give power to the other two props and slow down the front two, appears to make no difference. Tilting the drone forward or back appears to make no difference either in the speed at which the front props move compared to the rear two props.

The only way I can get the drone to react to the controls is to give the right stick full right or full left, which I can feel it wanting to tilt left or right, but the rear props still appear to be turning by just the movement of air generated by the front two props which appear to be moving at 100% (I can only guess that one of them is slowing down a little bit to get it to tilt that direction.)

I have checked the trim settings, all 4 props seem to spin freely when spun by hand, and I don't see any mechanical problems. I also double checked and all the props are all installed correctly on their corresponding motors.

What I can deduce by this is that the problem is probably related to the gyro and the controller thinks it's tilted forward so it's compensating by running the two front props at 100%. The drone in question is a u818a-1-p and the receiver, brains, speed control and gyro are all integrated into 1 unit. I have not yet taken it apart yet to see if I can get the model of the gyro so I can start probing with my oscilloscope.

I'm guessing that if the gyro does not output analog voltages for each axis, then it's using a serial bus. If it's using a serial bus then the gyro is probably damaged, if it outputs analog voltages then possibly there is a short or something causing the bad axis to go to either rail, or the gyro is damaged.

Am I on the right track here?
« Last Edit: July 03, 2018, 02:04:03 pm by jdraughn »

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