VCR Robot - Mechanics

Submitted by Ro-Bot-X on May 21, 2007 - 12:04pm.

 3. The mechanics. To keep costs low I have merged the chassis and electronics board together and mounted all on a perforated prototyping board. Besides the microcontroller, the H Bridge, the voltage regulator, a couple of nails and a few screws, all the other parts I pulled out from a couple of broken VCRs found on the side of the street. They were different brands, but inside they looked the same. I needed 2 VCRs because they rarely have 2 similar DC motors inside. But here’s what I got: 

DC motor with belt and wheels for the robot…

 VCR image - motor and belt  

 

On-off switch…

 VCR image - on-off switch   

 

IR photo diodes and LEDs, resistors and capacitors…

 VCR image - IR photo transistors and LED  

 

PNA4613 or something compatible, push buttons…

 VCR image - IR sensor     

 

And now, let’s see how we can attach wheels and motors to the chassis:

Robot image - nails soldered to the board  

Using a couple construction nails soldered to the perforated board as wheel axles! And drill 4 holes for each motor and tie it up with cable wraps! Don’t forget to twist the motor wires and solder 0.1uF ceramic capacitors between the motor leads and from the leads to the motor case. This will cut the noise to the circuit drastically:

Robot image - motors strapped to the board  

Then plant the parts, using sockets for the ICs. Solder everything. Then start to make connections between pads according to the schematic using thin wire. Insert shrinkwrap tubing around the LEDs to shield any side IR light that might influence the sensor.

Robot image - parts top

 

 

Robot image - parts bottom

 

Now we need a third wheel… Using a plastic bushing I had in a box and a piece of metal from a VCR I made a small caster for the robot. Using 2 small wood screws I attached the battery box to the board.

Robot image - castor wheel and battery box 

 

 

Insert the batteries and program the robot.

Robot image - batteries 

Let’s check if it is working… Yes! The on/off LED indicator is lit, wheels start to spin fiercefully!

Robot image - all done

Now let's see if the sensor is working properly. As you can see in the picture, the left LED is lit but the right one isn’t. And the debug window shows: Left 1  Right 0

Good!

Robot image - working

 

 

To see how I've programmed the robot, check out the Programming page...

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