Wiring a 5th servo to a Boe-Bot

jbyers

I bought the boebot setup and want to put the guts in another project. Ive programmed for years but never done robots. The issue I have is not with the simple language but the hard wiring. I want a 5th and 6th servo yet there is no place to plug them in on the default board. So my question is where can I find the documentation to wire in more servos? I looked all over and I'm at a loss. Thanks in advance!

Post Edited (jbyers) : 11/3/2008 4:55:45 PM GMT

Mike Green

Look at the schematic for the Board of Education (www.parallax.com/Portals/0/Downloads/docs/prod/boards/BOERevC.pdf). You'll see the servo connections in the upper right hand corner. You just have to duplicate these. The black wire from the servo has to be connected to ground (Vss). The red wire from the servo has to be connected to the servo (+) power source. The white or yellow wire from the servo has to be connected to some otherwise unused Stamp I/O pin. That's it.

Keep in mind that servos can draw quite a lot of current (over 1A each when under load) and you'll need an appropriate battery pack for them (usually 6V or maybe 7.2V). The power source for the BOE has to have the same ground as the power source for the servos. Connect them together.

sylvie369

I have a related question. In general, you want to power the servos from a supply separate from that used for the Stamp (or Propeller), right? So if I were setting up (say) a BS2 with four servos, I'd use whatever I normally use to power the BS2, but have a separate battery pack (like you suggest) to power the servos.

The control of the servos will be connected to a Stamp I/O pin, again, as you noted. Do the Stamp and the servos need to share a common ground? Or is the _only_ connection between the Stamp and a servo through that white or yellow wire going to the I/O pin?

allanlane5

YES, the Stamp and the Servo MUST SHARE A COMMON GROUND. Which means the Stamp ground and 'external' power supply will ALSO SHARE A COMMON GROUND -- through a two-wire signal-and-ground connection, if nothing else.

Sorry to shout, I just wanted to be clear.

Post Edited (allanlane5) : 11/3/2008 5:53:27 PM GMT

sylvie369

Sorry - I hadn't messed with servos until about two weeks ago, so I've been mostly ignoring the servo questions. I also thought it might be useful for our new member to see this: I don't think that it's obvious, and it's part of the answer to his question.
Thanks for putting up with a repeat question.

Edit: Oops - did Mike already answer it? And I just bleeped right past that part of his answer? My mistake.

Post Edited (sylvie369) : 11/3/2008 5:03:33 PM GMT

Chris Savage

Please use the pencil icon to the top right of your original message and add a descriptive subject.

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Chris Savage
Parallax Engineering

jbyers

Excellent!! Thanks for the quick response! I work with RC Boats that pull around 90 amps so 1amp is a breeze! Im using a 7.2 volt.