PDA

View Full Version : [Question(s)] MosquitIO Pan & Tilt Microcontroller twitchy



flemster
04-03-2011, 12:30 AM
Hi,
Just assembled a Desktop RoboTurret (http://forums.trossenrobotics.com/c/desktop-robot-turret.aspx) that I purchased before xmas/2010. The kit was okay to build and I'm working through the samples/tools. One thing I've noticed that I need help/suggestions: The unit is twitchy when not moving. From the moment it powers on the servos are constantly twitching a few clicks one way and then another. :sad:

Is there any way to cause the motors to stablize? It's very annoying, and is causing the camera mounted to have fits of focus problems...:confused:

Any suggestions are appreciated...

Rob

ROBOTMAN
04-08-2011, 11:18 PM
Are you using the included power supply or have you made any modifications to the setup like new servos, new controller, custom software? Also how large is your camera, a standard webcam or something much heavier?

flemster
04-09-2011, 03:39 PM
I've used the included 6v power supply and the web cam shipped with project. It is all stock parts that came with the kit. Using the demo programs I can move the servos, but when commanded to stay put, they constantly twitch.

Needless to say I'm most disappointed in the project. I"m not sure if it's the servos or the controller, but it is most annoying... Any suggestions?

REgards, Rob

mannyr7
04-10-2011, 12:43 AM
When returned to center, the analog sticks might have an imperceptible wobble from dead center, due to the return springs' tug on them and inaccuracies in the pots themselves. First off, though, which control solution are you using? the .NET application, Python and arduino sketch, roborealm? And secondly, what are you using as a physical controller? gamepad, phidgits joystick, or something else? Maybe you can try increasing the threshold before movement is applied to the servos in your code? But first we need more information.

flemster
04-12-2011, 10:25 PM
The twitching seems to be present at all times. From the moment the unit is powered with its 6VDC power source, without the USB being connected. Using the .net Dazzler sample, or the RoboRealm software, I can cause the hitec HS-322HD servos to move. But when I pause the movement the twitch returns.

If it was the pan or tilt I'd think it was a sensitive servo, but both twitch. and never stop until the power is disconnected. I'm at a total loss as to what to try next, and disappointed :sad: in the hardware kit. The software seems a good starting point for development, but if the camera will never steady itself, I don't feel eager to proceed. :genmad:

flemster
04-12-2011, 10:31 PM
For information purposes I ordered the RoboTurret Vision Tracking Starter Kit. No additional options. just the kit. which includes a MoszuitIO Pan/Tilt Microcontroller, the pan/tilt kit, Roborealm software, 2x hitec HS-322 servos, 6VDC, Robot Turret Kit, & LifeCam vx800..

Al1970
04-16-2011, 11:46 PM
Hi flemster:

I don't know anything about your kit but I do control servos using PICs. There are two things that can make them twitch.

1) If you don't put a 220 ohm resistor in the signal wire going to the servo from the chip; so make sure that your kit put one in.

2) If your program takes too big of a timing step. This can cause the servo to take a step sometimes and other times not, so this can cause it to twitch. I don't know if there is much you can do about that if you are using a pre built, programmed controller.

Al

tinman
05-02-2011, 07:23 AM
Mine is doing the same thing. I have another 2 at work I have to put together to test aswell.
I have seen this recently on a sketch with a Ardunio Uno.
It is the Ardunio internal code that caused my other issue.
The timing that pulses the servo can get delayed slightly by the interupt checking the serial port.
This was todo with the Ardunio IDE code.

Uploading the Ardunio sketch again with a newer version of the Ardunio IDE may fix this issue.
I'm trying this myself and will post if it fixes the issue.

Rod

tinman
05-03-2011, 05:21 AM
I haven't tested the other boards yet but it looks like you can't program the firmware through the USB. It looks like you need an Atmel programmer. I could be wrong!

But I have found that the unit drops its connection with certain brand keyboards.
I had it working perfectly last night on a microsoft keyboard but taking it to work with the same pc it would work for about 10 seconds then stop responding. I used a logitech keyboard and mouse at work.
I could reproduce this on other pcs too.
Bringing it home again it worked perfectly with the microsoft keyboard.

There must be some issue with some USB keyboards and mice conflicting with the servo unit.

rod

tinman
05-04-2011, 08:22 AM
Hi,

I have tested the other board and it has the glitches too.
Not that it really matters as the software searches for a Red object anyway.

But I found if you power the board and touch the other inputs/outputs it goes berko, zipping form side to side.
I'd say this is manual mode.

But still having issues with drop outs. It looks as tho it might be interferance being picked up by the board and loosing communication.

More testing needed.
But you can't complain for the price!

lnxfergy
05-06-2011, 03:00 PM
Could you post a video of the twitching? Low-cost servos often have a bit of a "whine" and occasionally a "twitch" since the electronics inside are basically from 1975.

-Fergs