Thread: 3 axis skull servo/cat 5 wiring

Tweet

Help.

I started wiring up four servos to a Propeller servo controller via Cat 5, reviewed everything I could find here and other places on the web, and am missing a step somewhere. I though I'd ask for help before I fry something.

On the skull side I have selected two of the Cat 5 wires for positive, and attached the positive wires from the four servos to these. Two wires on the Cat 5 are ground, with all the grounds from the servos attached to these. The remaining four Cat 5 wires are dedicated one each as a signal wire for each servo.

On the controller side I've run four positive wires off the Cat 5 positives and four ground wires off the Cat 5 grounds, and connected each to a female servo connector --thus I now have four female servo connectors with a positive, ground, and signal wire (one set of wires for each of the four servos). These are then plugged into the Propeller board.

The servos aren't responding, even to a stand-alone battery powered servo tester, so I'm missing something. Any ideas?

First I'll say that I am not familiar with a propeller board. However, I don't believe combining the wires at the skull then "breaking them down" into individual wires at the board again is going to produce the correct amperage to all the servos. Check your board's documentation for a single power source on the board that you can connect both positive and negative to power all servos. Usually there is a dip switch or jumper that can be set to do this sort of over ride at the servos for one power source. Then you won't have to worry about using the power at the Com ports at all. You'll just hook up the signal wire from the skulls. Send the positive and negative to the one power source.

Hope that makes some sense.

Gumba,

In my 3 axis I have 6 servos. So I was only able to use 1 wire for + and one wire for - .

The way you have described the wiring sounds correct. Just curious. Do the servo's work when connected directly to the prop board?

Is this the board you are using?

http://www.parallax.com/Portals/0/Do...Board-v1.3.pdf

I have never seen this board. What is it usually used for? Like an optocopter maybe? I see you have to add servo control to it.

I'm not familiar with this board either and I'm wondering what software you are using to control the servos. I think most people here use VSA (Visual Show Automation) to control their servos though. You have wired your servos with CAT 5 the same way I do ours. In the past I've had servos not respond because I needed to change the port speed setting in VSA from 9600 to 115200.

Thanks for the input!

The controller is by Parallax:

http://www.parallax.com/Store/Access...me,ProductName

The servos work fine when connected to the board directly. And, I'm using VSA. I have the baud rate set at 36000 (or something like that) and routines were going off without a hitch before I did the Cat 5 splice. I did not try changing the baud settings ---since everything worked fine before I assumed my wiring was off.

alucard, I'll look for a dip switch or jumper on the board, but judging from the other responses it sounds like what I described 'should' work----there is no additional wiring of grounds or otherwise that I've left off, huh?

Are you trying to power the servos from the board itself? You do need to provide a seperate power supply for the servos themselves, the board itself is powered by the usb port. What is the voltage and amperage of your power supply?

Gumba,

Looks like the board needs an external DC source. 4.8 to 7.5 volts. Just wondering if you have a voltage drop over the cat5 and you are dropping below logic voltage at the servos. I think your board may have a voltage regulator to put out 5 volts. That could be working against you. I would try a higher voltage first. If you have a 6 cell nicad pack you could try that. On the ssc32 board we have options to provide higher voltage to deal with voltage drop. If you are supplying your board with 5 volts, you could be seeing voltage drop.

Just curious. The ssc32 board costs $40 and is a proven board for animatronic use. Plus it works well with VSA. Do you have a reason you went with the paralax board? Does it record routines?

We use a power source that puts out a measured 6.6 volts. The power at the servos, after having traveled through as much as 40' of CAT5, comes out at 6.2 volts so we experience some power loss. If you are using a 5 volt source, it could very well be dropping below the voltage required to run the board and/or the servos.

So you only get a .4 volt drop ? If the supply voltage is regulated on the prop board to 5 volts, it would seem that the problem could be voltage drop. I would think wiring in a 6 volt battery like a 5 cell nicad in parallel at the skull would verify if it is voltage drop.

Spinman, I am curious about your statement " Do you have a reason you went with the paralax board? Does it record routines? " Does the ssc32 board record routines? I always thought that you needed a program such as vsa to run the board. If it does it may be worth looking into. I use the Parallax board and have had no problems with it. It will not record a routine or work as a stand alone controller though. I have not gone the cat-5 route yet but I will shortly.