Sunday 6 January 2013

Playing with the Pi

We'd planned to go out caching today, but ladysolly's back has been playing up, and we decided not to go. So I spent most of the day playing with the Raspberry Pi.

I got the Pi to switch LEDs on and off, and got it to detect that a switch had been switched. All this is moving towards Robot Arm Version Two.

I also found a bunch of LEDs in a drawer, and some other handy electronics stuff that I'd put away "in case it's useful one day".

I've built a webcam tilt-and-pan device. The shell of an old PC power supply is the base, and two of the stepper motors I got as spares will do the movement. I've ordered another Maestro stepper motor controller from Hobbytronics - the same one that I'm using for Robot Arm One. When I got the first Maestro, I wasn't actually sure that I'd be able to make it control the stepper motors; this time, I'm confident that it will work.

I still can't rotate the new Robot Arm. I can move all the other four movements, but not rotation. I tried a Python program in Magpi 3 (the online magazine for Pi People), and that had exactly the same problem. I'm baffled. I know the motors are working, because I can rotate the arm using the Windows program that Maplin supplied. And I know I have the USB protocols right, because I used a protocol sniffer in the Windows program; also, both the articles I've read about this device agree on what I have to send to make it rotate. And yet it doesn't move. Never mind, I've worked out a nice puzzle mission that doesn't involve rotating the arm.

Tomorrow, I'm planning an outing to Clacton. It's quite a way away, but one of the great things about Essex is that it's very flat - no hills to bike up! And I'll be most of the day on tarmac surface, so no squishy mud to bike over. Although I am planning to get into the countryside also, unless the surface is too soggy.

The worst surfaces for biking:

1. Loose mud that adheres to the wheels, jams into the brakes and you can't even wheel the bike, let along ride it. I'll willing to take the bike a couple of miles the long way round, to avoid a couple of hundred yards of this stuff.

2. Shingle. But you only get that on beaches.

3. Squishy mud that your wheels sink into. But at least you can walk the bike.

The best surfaces:

1. Tarmac, concrete and the like. Whoosh!!!

2. Gravel paths

3. Hard grass.

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