Over the last weekend I have completed the servo brackets but damaged 2 servos.
One of them because I was in a hurry to go somewhere and wanted to get it done. I didn’t take off the bracket to enlarge the central hole for the servo set screw, instead I tryed to do it on the robot. Of course, the drill bit got stuck exiting the hole and twisted in my hand, forcing the servo over it’s stop point, stripping a tooth from a gear inside. The servo still rotates, but I need to replace the gears.
Then, trying to figure the center for each servo and the extremes, I have noticed that they are not linear. They go from 0 to 180 but the middle is 80 instead of 90. So, the shoulder servos rotate in oposite directions and so do the arm servos. In order to make them rotate the same amount each step I needed some sort of equation which is hard to determine. So I had this great idea. What if I reverse the motor leads for all the servos on the right side? Easy to do, that will make the servos for both sides to respond the same for the same signal. But, after I did it, the shoulder servo started to go eratically… After a while, trying to figure it out, it got to me that I also had to reverse the wires of the pot inside each servo! That did the trick with the shoulder servo, but the arm servo did not work anymore… I measured the signal, power, resistance, but the conclusion was I fryed the chip. Oh well, at least they are cheap servos, I’ll just order new ones…
Other than that, I found out that I need to replace some parts because I am not happy with the way the torso bends down from the waist. The torso is too short and the waist rotation point is too high. Also when I’ll lower the rotation point, the torso will hit the scanning sharp sensor, so I need to mount it below the chassis board. It will be able to detect any low object on the floor, especially the objects the robot needs to pick up. I’ll replace the sensor with a short distance one that I allready have.
I found out that the Roboduino board needs a big capacitor just like Axon has, because it tends to reset at power up or when all servos move at once. As a quick fix I am going to attach a capacitor to a 2 pin female heather and plug it on Roboduino on the unregulated power pins. Hopefully it will solve the problem.
I wish I had the chest plate taller so I can mount the LCD above the shoulder servos, so I have it like a graphic interface before I’ll start playing with text to speach chips.
I need to figure out a way to store and play servo movements, like waving an arm saying Hello!, grabbing an object from the floo, doing some dance moves and so on. After I’ll have the basic moves I’ll start playing with the AVRcam, but it will take a while until I’ll get there.
So here are some pictures of the robot: