Despite the fact that the motors are physically TINY, they seem to have enough power to carry Bernie around fairly comfortably. Better yet, I have got the program to work so that the analog joystick on the Playstation controller operates the two motors and lets me steer! I expect he will get slowed down once he is dragging the full load of skin and wings and his tail is reattached, but for now he is pretty zippy.
I have been busy working on giving Bernie a way to get around. He won't be autonomous (that's a whole other level of complexity and honestly I don't need a dragon who can move around when I'm not there, that's just going to lead to disaster!), but he will be able to move around on wheels under control from the Playstation controller and he has four legs to crawl around on.
Each leg has a bearing joint in the knee/elbow, which is made up of a screw, nut, some washers and most importantly one rivet attached to each piece of wood to allow the parts of the leg to move around the screw without too much friction.
Once in place, the bearings work very nicely for letting the leg move, but they initially didn't do much to stop the leg splaying out to the side, so to avoid this I added the third rivet which you can see in the top picture, as well as a second section of the lower leg which is supported by a 6mm spacer (just visible in the picture on the left) to allow the joint to move freely around the screw without moving sideways. I also replaced the nuts with nyloc nuts so that the repeated rotation and vibration doesn't continually loosen the joint. This way tightening the nut on each joint gives me very good control over how much resistance the joint offers to rotation as well as how much the lower leg wobbles around.
Reconnecting the legs to the body and wiring up the servos to the arduino made it very simple to test out a basic walking motion. The timing still needs some work, and without the wheels and tail to provide resistance the whole body has a tendency to wobble around, but the basic idea is there and the pulley system seems to be working nicely.
To make the legs move a bit nicer I need to make the hips more rigid by adding some blocks around the join to the spine and also reinforce the screws joining the servo horns to the hips. hopefully I will have that done by the end of the week and can move on to the final programming of the walk motion.
Did you notice he's not actually getting anywhere? I have some lovely little micro geared motors and wheels from pololu (bought through littlebirdelectronics) which I have wired up through an ardumotor shield and will be mounting as soon as possible, however the scroll saw is out of action for the moment so I can't cut the recesses in the body to mount the axle supports. These will also raise the body off the floor by about 15mm so the legs can move more easily without rocking the body from side to side.
In a very exciting moment I connected a Lynxmotion PS2 wireless controller via a Lynxmotion PS2 receiver to to the arduino, installed Bill Porter's wonderful PS2X library, supplied power to the arduino and the outputs and downloaded the example program and - TA DA - I have remote control of my arduino, which means very very soon Bernie will be operated remotely. Many many thanks go to Bill for this lovely little library which makes this all so easy to do.
On a side note, having looked at the price of battery chargers and batteries it might be a while before he is moving around completely remotely...
This week I made the first step towards a speaking (or roaring) dragon by soldering together the wave shield from adafruit industries and testing some of the software. Using the example code audio files, burnie now has the ability to recite pi to... well a lot of digits.
Those aren't just untidy yellow wires either - unfortunately the wave and the arduino mega are not naturally compatable, so there was a little bit of extra soldering and software configuration to get this running. Nothing a bit of debugging and some helpful forum folk couldn't fix.
The audio is a little quiet (who ever heard of a whispering dragon?) so I'm going to have to build an amplifier, but this will work for now so that I can get on with some other construction developments which are underway.