Hardware > Bobcat DMX Servo Controller
Bobcat 6V power supply
JonB256:
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Register or LoginI haven't tried it, by my plan is to use 5v.
I have plenty of that available from the pc supplies I'm using for my smartstrings.
RM
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RM, I'll toss this idea at you. The main reason to use 6VDC instead of 5VDC would be rotational speed. It will have a bit higher torque at 6VDC. You mention using PC power supplies, and that is my plan, too.
What I will probably try is this: Remove the jumper that splits my power inputs and then put 5VDC on the Logic Side. That solves the "brown out" concern mentioned in the Wiki. To power the Servo side, you can use the 12VDC line as Positive and the 5VDC as the Negative (as if it were the ground/negative wire). The difference voltage will be 7VDC !! That one volt bump over 6VDC will improve torque and speed and, being only one volt, should not damage your servos. Many people run them at 7 to 9VDC anyway.
I have done this before and the servos survived just fine, but I haven't tried it with the Bobcat (yet). I just finished soldering up #1 of 4 tonight, so will be powering things up soon. I've got Halloween skull plans.
rm357:
I can't look at it right now, but I don't think that's going to work.
First, I think the two grounds are the same. If they are, when you hook 5v to the servo ground terminal, you will short out the power supply.
Second, I'm not crazy about using the difference between the 5 and 12 volt power rails to get 7 volts. The 5 volt rail is meant to source 5 volts, not serve as the sink for another power rail. For small currents, maybe, but you start pushing much power into the 5 volt output, I think you are going to have issues... If you've got a big enough load on the 5 volt rail to ensure that current never gets pushed into the output, that might work, but I'd consider it risky to run it that way.
RM
n1ist:
The two grounds *are* the same, so that technique won't work.
/mike
JonB256:
After sketching out the power, it would definitely be a problem if you split the power. It would work only if you connected the +12vdc to the Servo positive and the +5vdc to the Servo negative. Nothing on the Logic side, so the jumper stays in place.
While this would put 7vdc to the servos, it would also make the voltage regulator work harder.
So, I would probably just run the whole board from a 5vdc connection if I didn't have a good 6vdc power supply.
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JonB256:
Tested the 3 Servo controllers I've finished (one to go!) and all 3 worked fine.
Used a 6Volt Lantern battery for power and two Futaba S3003 servos.
I was a bit concerned at first when, with power applied, I got no green LED. Once I plugged in the Bobcat Tester, though, it started slowly flashing. I was wondering if I'd remembered to flash the PICs!
Plugged in the servos and immediately got motion! Using the Bobcat tester, I quickly found that #1 worked perfectly.
Then, #2 got connected and it worked perfectly. Then #3 also worked! I suppose I'll work on #4 soon, though its more channels than I have planned for Halloween.
I'll play with the servo config utility soon, though. I'm only getting 90 degrees of rotation from 0 to 255. I was hoping for 120, so I'll play with that.
All in all, I'm happy that I have some nice featured DMX Servo controllers and should definitely get some good feedback when my usually static skulls begin turning with the music and following people with their glowing eyes as they walk by.
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