usb servo controller

jim michelau

I just got my new servo controler and I'm having some problems.··I've installed the drivers·and it is comunicating on a virtual comm port.· The lights glow red·with usb connection and·when I adjust the PCSI software controls the green light blinks. The servos, unfortunatly, will not move.· I'm using a 4 pack battery(aa) to power the servos.· On more thing, when I click 'Get Version' the window reads 'Version ...'.· Any help even if its bad news would be appreciated.

jim

Chris Savage

Jim,

·· What position is the jumper next to the reset switch in?· Is should be open.· If it is, try to control your servos as if they were addressed 16-31 to see if that works.

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Chris Savage
Parallax Tech Support
csavage@parallax.com

jim michelau

The jumper is set to off, but, I tried both jumper settings and still can not get motion from the servos. I've tried, without luck, both a standard(tower mg995)and a micro servos(generic). I've rotated the servos by hand without being connected thinking the servos might have reached a limit, this solved nothing. Can it be a power issue? Are the batteries enough, or should I use a transformer? I woulld need to know the transformer amperage. At last attempt I can hear the servo respond to powering up the controller. It sort of 'jiggles' for half a second then nothing. I must be doing (or did) someting wrong, I just don't know what it is. Thanks in advance for any help.

jim

Chris Savage

By default when the PSC is powered on and servos are connected (and powered) they center.· If this isn't happening, or you can move them by hand, there is a problem.· Most likely a power problem.· Are you sure of the voltage and current of your servo power supply?

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Chris Savage
Parallax Tech Support
csavage@parallax.com

jim michelau

I can't move the servos by hand when powered up. I am not sure of the power source (4aa) but the (unused) original battery pack that came with the servos is 10.8 volts 650mah. Can you recommed a dc power supply amperage(max) I could try? Again, my servos are Tower Pro MG995 high torque if that helps.

thanks
jim

jim michelau

If this helps this is the specs for the servos I'm attempting to use.
I would like to use as many as 16 of these servos. Is there an amperage limit for the controller? I would like to use a simple plug in transformer but I do not want to 'over do it'.


Dimension : 40.6mm*19.8mm*37.8mm
Weight : 1.78oz (48g)
Operating Speed (4.8V no load) : 0.17sec / 60 degrees
Operating Speed (6.0V no load) : 0.13sec / 60 degrees
Stall Torque (4.8V) : (13kg/cm)
Stall Torque (6.0V) : (15kg/cm)
Temperature Range : -30 to +60 Degree C
Dead Band Width : 4ms
Operation Voltage : 3.5 - 8.4Volts

allanlane5

The way a servo works, it has a Power connection, a Ground connection, and a Control connection.

The major amount of current goes through the Power and Ground connections. The Control connection (the one the controller is connected to) takes very little current. So, the controller doesn't have an amperage limit, because the amperage should be going directly from the battery to the Power line.

OK, but you STILL need to know the current the Servo's pull on the Power line when fully loaded. Which you don't have the spec for yet.

The only reference I've been able to come up with show 8 mA 'idle' and 350 mA when moving with no-load. Loaded currents can be much higer -- 1 amp per servo? Testing this would be the best way of finding out.

For 16 of them, you may want separate wall-wart supplies for each 'clump' of 4 servo's. Or a single 20 Amp supply. Make sure all the GROUND wires are connected together some-place, but the Power should be routed point-to-point.

Chris Savage

As a note when you mentioned your power supply specs the USB PSC is rated at a maximum input voltage of 7.5 volts on the servo power.

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Chris Savage
Parallax Tech Support
csavage@parallax.com