usb servo controller

Comments

• Chris Savage Parallax Engineering Posts: 14,406

  2006-02-03 15:17 edited 2006-02-03 15:17

  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 Posts: 4

  2006-02-03 16:05 edited 2006-02-03 16:05

  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 Parallax Engineering Posts: 14,406

  2006-02-03 16:10 edited 2006-02-03 16:10

  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 Posts: 4

  2006-02-03 21:43 edited 2006-02-03 21:43

  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 Posts: 4

  2006-02-04 17:26 edited 2006-02-04 17:26

  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 Posts: 3,815

  2006-02-06 15:45 edited 2006-02-06 15:45

  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 Parallax Engineering Posts: 14,406

  2006-02-06 17:57 edited 2006-02-06 17:57

  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