Let's Make Robots!

I think i killed my servos

I was working on an object tracker with a sensor board on a servo.
The servo is controlled by a picaxe.
This is the program:

  servo 0,150
  pause 20
  goto main

(its actually more, but for testing i limited it to these rows)
Now when i attached the servo it somehow went crazy and keeps spinning around,...
So i thought, maybe its the servo.. lets try another one.
Bam.. same thing.. keeps spinning around.

L293D question

I have build my own board with a PICAXE-18M and L293D motor driver.
The motor driver uses a seperate power source to power the motors.
When an output signal from the PIC is send to the L293D a LED shows the output is high.
All seems to work without problems; the motors do exactly what i tell them to do and so do the LEDs.

Servo torque question

I'm planning to build a robotic arm and need to know what servos to use.
Can someone tell me if my math is correct here?

When i take a servo that has a torque of 240 oz-in (17 kg-cm) and use that as shoulder joint.
A 20 cm long arm would be able to lift a maximum of 17 / 20 = 0.85 kg ?


This is my first real attempt at robotics. I do have my own bot design in mind, but i decided i should start with something small. I'm really a learn-by-example … Read more

Battery charging question


I have build my first robot (simple hexapod).
It uses an 4.8v 150mAh NiMH battery pack but i have no charger for it.

Any suggestions on how to charge that battery?
Do i need to buy a special charger for it or can i just hook it up to a 5v adapter and let it sit for a bit?