Sumo and extra servos
I'm trying to use the sumo bot kit for a custom project, and I need to use an additional servo. I tried connecting a spare servo I had from a Boe-Bot kit to the X3 port (B, 2, 3) instead of one of the typical servo motor ports (X6 and X7, which are respectively labeled as B, R, 13 and B, R, 12). When I want the servo to rotate, I assumed that one of PIN 2 or 3 should always be high and the other should be sent a pulse train. However, this didn't work, and neither did keeping one of the pins low.
I realize I'm doing something very stupid here, but any pointers would be appreciated.
I realize I'm doing something very stupid here, but any pointers would be appreciated.
Comments
·· When controlling a servo, you set a given pin (The one you have the servo's signal line connected to) low, then send the PULSOUT to that pin.· Since the X3 port does not provide power, you will need to get power for the servo elsewhere.
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Chris Savage
Parallax Tech Support
csavage@parallax.com
Post Edited (Chris Savage (Parallax)) : 3/27/2005 4:30:12 AM GMT
·http://www.parallax.com/dl/docs/prod/robo/sumobotman.pdf
you'll see that the black wire of your servo connects to ground, the red (middle ) wire connects to Servo power, and the white or yellow wire connects to a stamp pin. don't try to power a servo through a stamp pin- not enough juice and you could hurt your stamp.
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That pin is set as an OUTPUT, normally LOW. Then to position the Servo you send a PULSOUT of from 1 mSec to 2 mSec duration -- 1 mSec is all the way left, 2 mSec is all the way right, 1.5 mSec is center -- and repeat that signal every 20 to 50 mSec.
And having a separate power supply drive the Red wire (with its ground connected to the BS2 Vss or GND) is a good idea, as the servo takes more current than the BS2.
Thanks again!
Note you might want to connect your additional servo power to "Vin(2)", especially if Vin(2) is actually supplied by a different supply than the one supplying the BS2.
If Vin is 6-volts, and doesn't go through a regulator (like Vdd does), then you can get more 'oomph' from the additional voltage, and it affects your BS2 less, if your servos draw directly from Vin. So I wouldn't connect my additional Servo to Vdd, I'd connect it to Vin (IF and ONLY IF your Vin is 6-volts -- which since your other Servo's are tied to it, seems true).
AHA!· I just looked at the schematic for the Parallax SumoBot -- you want to supply your third Servo power from Vin(1) -- which you have a jumper socket for, NOT from Vdd.· Otherwise, you have it exactly correct.
Post Edited (allanlane5) : 3/27/2005 3:43:56 AM GMT
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Jon Williams
Applications Engineer, Parallax
Dallas, TX· USA
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Chris Savage
Parallax Tech Support
csavage@parallax.com
I ended up using Vin and doing everything else as specified in the diagram, and it works!