I’m actually powering my Pi using a Pi-Hub by Pimoroni – http://shop.pimoroni.com/products/pihub

It claims to be rated at 3000 mA.

At the time nothing else other than keyboard and mouse were connected to it. I agree the results were not as expected.

Thanks for the response.

Mark

I finally got a chance to test this tutorial with the new Model B+ this weekend, but didn’t get any lockups. The steps I took were

• I started with the latest version of the Dawn Robotics SD Card image available here (2014-07-18). This is basically the June 2014 version of Raspbian with a lot of our open source software installed.
• I installed RPIO and the pi_pan_tilt_control script as detailed in the tutorial.
• Probably most importantly, I used this 1.2A power supply from RS Components

With this setup I was able to run the control script and didn’t get any lock ups at all.

It’s interesting that you were able to run the servos from the Pi on a Model B, but not on a B+ Mark, as in theory the Model B+ consumes less power, and so should have more to spare for the servos. Do you have a link to the wall adapter you used? As if it’s not too much I might buy one to check it out.

Regards

Alan

Loving the kit, learning about it all the time. A bit fiddly to setup for my fat fingers as initially I forgot to add the washers!

As a point of reference that might help people. I tried this initially on a Raspberry Pi B+, had lots of lock ups and reboots, I figured a power issue. Tried the EXACT same setup on a ‘B’ model, (same GPIO Pins etc) with the same supply and the script worked fine. So if using a Raspberry Pi B+ I would advise using an external power source. I found using a power supply from a crappy powered hub I bought provides a reasonable 5V to use. (Just share the common ground!)

This sounds a bit odd. Perhaps a bug that’s crept in due to a change in a recent version of Raspbian. Could you maybe try running the script on an older version of Raspbian or one of our older SD card images?

I’ll hopefully have some time to look at this later in the week so that I can check it’s still working on our Pis.

Regards

Alan

If the problem can be solved by switching to external power for the servo, then it defintely sounds like your wall adapter can’t deliver enough current. Basically if the current drawn by the servos gets too high then the voltage supplied to the Pi will drop, and it will brownout, shutting down and restarting. The current draw from the servos will increase if they have to change direction quickly or if they’re stalled (i.e. if you stop them from moving with your hand). The wall adapter I tend to use is this one from RS components so it may be worth getting one for your Pi projects.

As for the servo buzz, that is fairly normal for servo motors I’m afraid. Basically the motor control electronics inside the servo are continually seeking back and forth past the target angle, although hopefully you shouldn’t see too much judder. It may be possible to turn off the PWM signal to the servo once you think its reached its target angle which should stop the buzz. But then the servo wouldn’t be held in place and could be turned by hand.

Regards

Alan

I tried the Pi with a wall adapter, and same problem. Additionally, the problem happened both when issuing rapid commands (such as having mouse position drive servo position), and issuing sparse commands (such as command-line mode.

The problem can be solved by switching to an external power supply (or presumably, adding something between the Pi’s vcc pin and the servos? Can you advise?). As I say I’m a total electronics newb so I’m not sure exactly what the problem was other than it doesn’t happen when you draw power from an external source. Perhaps it tries drawing too much power and overwhelms the Pi?

Thanks for your continued speedy replies, will definitely be placing further orders

p.s. the servos “buzz” when maintaining position, I assume that’s normal operation…