I am running two 3-axis skull props using a SSC-32 and VSA. Each skull has 6 servos - one set of 6 is on PINs 0-5 and the other set of 6 is on PINs 16-21. I want to add LED lights to the inside of each skull and am using a 3-LED RGB cluster for each skull. These clusters were part of the skulls I purchased for this project and initially each ran off of 2 AA batteries. The clusters are mounted on a small circuit board with resisters included. I removed the LED clusters from their original battery housing and wired them to female connectors that will plug in to the PINs on the SSC-32 with the positive (+) side of the RGB cluster going to the pulse PIN and the negative (-) side going to the ground PIN (the center power PIN is not used). These will be plugged into PIN 15 for skull #1 and PIN 31 for skull #2. I set VSA to control these two PINs as SSC-32 Relays using 0 for off and 1 for on. I have a single 6V power supply controlling the SSC-32 board connected to the center power connection with the outer two power connections jumpered to use the center. I tested this setup on one of the skulls and it seemed to work fine.
My question is this: (1) Does this sound like a valid way to connect the LEDs so that I can controll them as part of the VSA routine? And (2) should I be aware of any possible side affects such as overloading the board? I don’t want to chance burning up the SSC-32 controller board.
Thanks for any information.
Mike
The SSC-32 uses a 74HC595 for the outputs. That part is limited to 35mA per pin, but a max of 70mA per device, (each bank of 8 outputs.) For your reference the SSC-32 manual includes this information.
Just so I understand, since I have each LED cluster as the only item plugged into a bank of outputs (one in PIN 15 and one in PIN 31 with nothing else in those banks) then I am safe as long as each cluster is less than 35mA, correct?
Also, was I correct on my wiring? - positive side of the cluster to the pulse PIN and the negative side of the cluster to the ground PIN? I vaguely remember from another post that maybe it should be positive side of the cluster to the power PIN (center PIN) and the negative side of the cluster going to the pulse PIN. Can you confirm which is correct?
Thanks…
Mike
Both are correct. In open collector outputs it’s only possible to sink current, but not source it. So it was very popular to connect the cathode of the LED to the output and the anode to 5vdc through the resistor. However with the chip used in the SSC-32 I believe it can sink or source the same amount of current. However with the SSC-32 you don’t want to source the current from VS because it’s not 5vdc.
It’s 35mA per pin on each bank of 8 with a maximum of 70mA for all 8 outputs. If you add resistors for the LED’s to reduce the current draw to say 7.5mA you can attach 4 LED’s per bank.
Jim, sorry - you are dealing with someone with little electrical background so I am not familar with the terms sink and source current. The way I view it is each output has three PINs (pulse, power and ground). Right now I have the cathode (negative) side of the LED cluster going to the ground PIN and the anode (positive) side of the LED cluster going to the pulse PIN. Do I understand you to say that it will work this way and will also work with negative side going to the pulse PIN and positive side going to the power PIN? If so, is one way preferred over the other? My power source is a single 6vdc wall pack connected to the VL pins with both VL=VS jumpered and VS1=VS2 jumpered.
Sorry for redundancy…
Mike
You want to source the current. This means you connect the cathode to ground, and connect the anode to the I/O pin with a resistor in series.
Cathode = Negative
Anode = Positive
Just to help clarify.
I’m just wondering if you’ll get enough current to make the LEDs bright enough. Remember, the duty cycle out of an SSC-32 pin is already just 1/8 (each motor refreshed once in a 20 mS frame), and then it’s the PWM duty cycle (0-255 / 255) on top of that.
You might want to fire up a few LEDs with the SSC-32 and see how they do before committing too much. Increasing the current (smaller resistor) will help with the brightness, but the 74HC595 chips probably won’t like that too much. The LEDs can “average” the current (so to speak), and handle it, but maybe not the drivers. Of course, you could switch to a transistor driver, and treat them much like a multiplexed setup.
Alan KM6VV
That would be true if he were using servo position commands to turn on and off the LED’s. But infact he’s using the built in H/L commands that make the signal line go high and low. 
From the SSC-32 manual…
The channel will go to the level indicated within 20mS of receiving the carriage return.
Discrete Output Example: "#3H #4L "
This example will output a High (+5v) on channel 3 and a Low (0v) on channel 4.
“I.O pin” = pulse pin I assume?
If so it sounds like I have it wired up right. What had me wondering was during testing, the LEDs lit up at the beginning of the routine but went out half way through, even though no command was sent to turn them off - the servos all continued on fine. the next time through the same routine they stayed lit the whole time so i thought maybe I had hooked up something wrong. Maybe just a loose wire… 
Mike
That would at least give the LEDs enough current! Might get a little busy trying to give them enough on/off commands to give them some dimming control, 'tho. I had thought he was attempting to imitate a LED controller chip. That might be a different thread.
Alan KM6VV
Yes I/O pin is the pulse pin. It depends on a lot of things, like your power, wiring, load, battery, sigh… If your program is sending servo positions continuously and the SSC-32 resets, then the LED’s could go out until the SSC-32 receives another command to turn them back on. I’m assuming the servos were receiving commands the entire time which would mask them losing position for a short time.
Yes, all of the servos are in continuous motion. Would it be better to hook up a 9v battery for the logic and use the 6v wall jack for the servos and LEDs or should the 6v wall jack be plenty for all?
It would be better to hook up a 9v battery for the logic and use the 6v wall jack for the servos and LEDs if you continue to see weird things.