How to Build a Robot - The BeetleBot v2 ( Revisited )

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Step 12: The BeetleBot v2 ( Revisited ) - The third connection ( part 2 )

Picture of The BeetleBot v2 ( Revisited ) - The third connection ( part 2 )
beetle_robot_v2_2007_MAKE_ 079.jpg
Here is the principal and most important thing about the beetlerobot.

It is call the "third connection"

In you AA/AAA battery you have 2 wires that provide 3Volts.

In reality, we only use 1,5Volts for both motors.

How can we get half the voltage? Simple, you solder a wire like the picture below.
The new wire will touch the last wire you have solder in the last step and you will connect it to the battery holder. See picture.

Be very carefull when soldering to the battery holder, you can melt the battery holder! I have already done that. This will happen with cheap AA holder.
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ktech954 years ago
also.. when both the sptd switchs are pressed both motors turn off....
ktech954 years ago
plz help when i connect the wire to the back of the holder only one motor turns on and that too it stops after a few seconds...
gchadha4 years ago
mr dermers
my both motors stop working when i press even 1 of the spdt switches.

and the rotors have a very slow speed
TobbaBK6 years ago
This "third" connection, is it negative or positive? I think it's both but I'm not sure..
robomaniac (author)  TobbaBK6 years ago
It is both!
I was unclear about this too. Comparing the picture to my battery holder, it looked like the connection was to the negative post, but that didn't work.

Once I reviewed your great drawings of how the switches reverse the polarity of the motors, I realized this third connection needs to go to the tab that connects the negative terminal of one battery to the positive terminal of the other. Worked like a charm.

In my case, I didn't even have to solder it. The wire squeezes nicely between the metal tab and the plastic.
 oh thank you chrispix! i get it now
BenBot6 years ago
I got this far but then noticed that my battery holder does not have two openings at the base as in your picture - it's solid plastic. Should I go around the bottom and connect the wire to the metal, or will that interfere with the battery working when I try to install it? What exactly am I supposed to connect to on the battery holder? This is for my science fair project so please reply soon! Thank you.
 just drill a small hole in the battery pack.
I just cut a notch and soldered it to the battery contact in the holder
doc.v BenBot6 years ago