Thursday, December 30, 2010

Chapter 5 - Experiment 32 Do Over


Well, I finally managed to grab some time to get back to the circuit on page 277... I bought a smaller breadboard that will allow me to mount to the robot (if I can ever get this thing working) and not have to solder every component... saving me some aggravation if debugging is required.

As you can see from the video, I've made a giant step forward - the motor spins forward until either of the switches is pressed... if the switch is held down, the motor reverses direction and continues reversing until the switch is released. But...

This isn't how it's supposed to work. When the robot hits a wall or table or other obstacle and a microswitch is pressed, the robot is supposed to reverse direction for about 5 seconds (more on that in a minute) and then move forward again... the wheel mounted to the moving pivot is supposed to help the robot find a different (random) direction to move.

Now, a few things that may or may not be affecting this circuit - first, I don't have a 0.01 uF capacitor for C2 in the circuit - I have a 0.1uF ... but I do have a 47uF cap for C1. If I understand the 555 chip correctly (referring back to page 157 for monostable mode) - a 47uF cap is on pin 6... and I've tried the 100K potentiometer at both settings (using a screwdriver to maximize and minimize the resistance) but no change.

I'm going to go back and take another look at my circuit, but I've double checked all of the circuits resistor values and all my wiring of the 555 and the relay. Because the motor is spinning forward UNTIL a microswitch is pressed, I think I'm close to getting this to work... but why it won't spin in reverse for the full 5 seconds still alludes me...


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