Replies to This Discussion

3D RoboticsPermalink Reply by Chris Anderson on July 25, 2010 at 12:36pm

Can you explain what you mean by "funky" and "not good values"? It's a little hard to diagnose without actual data.

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Permalink Reply by Ricardo Madera on July 25, 2010 at 12:42pm

It sticks to values 8192 (raw) or 0. With the configurators it ranges between -1,1. Also I just noticed changing the offsets in the ArduCopter build wont add or subtract values.

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Permalink Reply by Ricardo Madera on July 26, 2010 at 4:31am

Really odd, but i think some solder point on the board must be loose. I was holding the APM and moving it around and watching the results in the configurator. Whenvever i put a tiny bit of pressure on the relay (just holding the board here) the gyro would start getting proper readings.
Im considering giving the board a quick blow with a hot air gun.

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3D RoboticsPermalink Reply by Chris Anderson on July 26, 2010 at 7:14am

Yes, sounds like a hardware fault. I'd contact Jordi at the DIY Drones Store to arrange for a return.

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Permalink Reply by Ricardo Madera on July 26, 2010 at 8:16am

Ok, i just sent Jordi an email. I will be holding out on the hot air gun until i get a reply from him. Although, It does seem like an onboard solder point is not making contact unless the board flexes a tiny bit.

Thanks for the help!

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Permalink Reply by Andrew Robinson on July 27, 2010 at 7:21am

I'm having similar issues with my Z-axis gyro. It is exhibiting very odd behavior. The gyro will be in one of two possible states:

State 1:
It will report 0V with no response to Z-axis rotation.

State 2:
It will report a nominal 1.3V and give the correct response to rotation.

I can find no clear correlation between any event and the determinism of the gyro's state. For example when started up it falls into state 1 or 2 pretty randomly, with a tendency to fall into state 1 80% of the time. The gyro will also randomly transfer between those two operating states while powered up. One second it will give proper readings, the next it will not.

I'm also holding out on the hot air gun, hopefully the store is good about doing returns. I have also confirmed that the pins seem good. I would love to diagnose further but I fear doing so will invalidate any sort of implied warranty I have.

Plan B is to order the part from InvenSense and put the board through a reflow cycle, although that is risky, I can't imagine the accelerometers and gyros enjoying multiple reflows... once to get it off and once to put it back on.

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Permalink Reply by Ricardo Madera on July 27, 2010 at 8:05am

I agree, did you try putting a bit of pressure on the board like i did? Hold the board with 1 finger on the relay and the other under the APM and very** lightly press down. Does it switch states like that?

Let me know if you manage to get a hold of jordi through the store email. I sent him one yesterday but still waiting on the reply.

When did you receive your shield? (maybe a faulty batch?)

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Permalink Reply by Andrew Robinson on July 27, 2010 at 8:12am

I haven't received a reply yet, e-mailed yesterday afternoon.

I did notice some difference in measurements when applying pressure on the relay but they were small ~10-20mV changes, most likely from the stray capacitance injected from my fingers into the circuit.

My order shipped the 14th of July.

I think the charge pump regulator in my gyro might be faulty. The reference voltage also falls when the output of my gyro does. The signal has a decay time of approximately 1 second or so, I've verified that the device still responds as the voltage output decays... it's as if the whole circuit is slowly discharging.

I also see a ton of AC noise on the line when the voltage drops.

Have you looked at the voltage output on your ref pin when the faulty readings are taken?

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Permalink Reply by Ricardo Madera on July 27, 2010 at 8:37am

Nope, I need to head up to the lab at school for that. Its really hard to do during the week since im working this summer. I will try to head up there today if i have some spare time and get those measurements.

Although, I am not sure what the "charge pump regulator" is. (care to explain?)
As a CS major, Im a little new to the ECE side of embedded systems =P.

The ref pin you mentioned is the 3.3v aref on the shield?

[EDIT] I just got an email from the store, it seems they will be happy to exchange it for another. I ordered mine on the 15th, so it actually might be a faulty batch.

Permalink Reply by Andrew Robinson on July 27, 2010 at 9:26am

Yes.. I've gotten an RMA number too. I suppose it'll be two weeks now until I see a replacement. :-/ I was really excited to fly too!

A charge pump regulator is just a type of regulator, much like a LDO regulator such as the 3.3V fellows on the oil pan. It serves to produce the reference voltage used by the gyro.

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Permalink Reply by Ricardo Madera on July 27, 2010 at 10:14am

I know how it feels =/. this will be my 2nd downtime period for this project. Last time i flew, i crashed it upside down and destroyed my APM. My shield survived apparently but with all the LED's shattered (I still ordered a new one which came with the broken gyro). I think i will try to replace the LEDs and test it while the RMA is being processed.

What code are you using to fly? ArduCopter? Aeroquad? or did you write your own?

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Permalink Reply by Andrew Robinson on July 27, 2010 at 11:19am

I'm using modified ArduCopter w/ I2C ESC output and additional telemetry module I wrote for high speed binary-based XBee communication that I'm still tweaking. I've also played around with the vector library for speed.

Tempted to write my own though, writing from scratch would be fun. I'd like to redo the DCM-based approach using quaternions to cut down on calculations (although I admit I have not done the research, perhaps there is a reason why the 3x3 matrix representation is used) and some other improvements for speed. Arducopter is for PWM-based ESCs with slower response times. I could benefit from fast response time of I2C ESCs for greater stabalization.

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