I was thinking about building a robot out of 4 continuous servos but would i have to use 4 I/O lines or could i just connect 2 servos to the same I/O line?
No problem connecting the two signal lines together. You'll want to be sure they are carefully centered (not moving with a 1.500mS pulse) and if you are really picky you may want to try different pairing combinations in order to select two servos that respond most similarly to the inputs. For example, one servo may move a bit faster at the same pulse width than another.
On my 4 wheeled robot using 4 continous rotational servos, I developed over the past year, I used what is called a y-cable/harness. THey are available at most hobby stores and are often used by model airplane guys to control 2 servos from one channel or in your case one I/O pin. This will work if you want the servos to turn in the same direction.
I have since moved to using a Prop Servo Controller Board which works great and releaves the load on the BS2 of driving the servos.
I hope to reveal my robot soon on this forum. I have it roaming with a ping sensor on a BS2. It is four wheel drive (using 4 continous servos) and has four wheel steering. I am going to work on developing a Spin Stamp (Propeller Stamp) version this weekend. I'd like to produce and sell the chassis as a kit.
Is the idea of putting two servos on one line to increase the torque? College is 23 years ago so my physics is a bit rusty, but do you simply add the torques of the two motors together? If so then I can see how this would be handy for building a bigger robot out of smaller cheaper parts.
Also you would be consuming twice the current, so what are the battery implications? For example I thought that current is an issue of chemistry of the battery and not its size. So D cells and AA cells supply the same current, but D cells can do it for a longer period of time. Or is that not true?
I don't know that I would use a second servo to increase torque. To gain torque I would use a more powerful servo. I used the second servo to add four wheel steering to a RC car.
That makes sense. I saw a lego robot with synchro drive where they used linkages to turn all wheels at once. Then one of the wheels was a drive wheel and moved the robot in that direction. I could see how four servos would simply the mechanics considerably.
Comments
Rich H
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The Simple Servo Tester, a kit from Gadget Gangster.
On my 4 wheeled robot using 4 continous rotational servos, I developed over the past year, I used what is called a y-cable/harness. THey are available at most hobby stores and are often used by model airplane guys to control 2 servos from one channel or in your case one I/O pin. This will work if you want the servos to turn in the same direction.
I have since moved to using a Prop Servo Controller Board which works great and releaves the load on the BS2 of driving the servos.
I hope to reveal my robot soon on this forum. I have it roaming with a ping sensor on a BS2. It is four wheel drive (using 4 continous servos) and has four wheel steering. I am going to work on developing a Spin Stamp (Propeller Stamp) version this weekend. I'd like to produce and sell the chassis as a kit.
Hope this helps,
Tony
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Ron aka sailman58
Also you would be consuming twice the current, so what are the battery implications? For example I thought that current is an issue of chemistry of the battery and not its size. So D cells and AA cells supply the same current, but D cells can do it for a longer period of time. Or is that not true?
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Ron aka sailman58
Post Edited (Martin_H) : 3/4/2010 1:44:29 AM GMT