Sparkfun PWM shield: power and servo issues

Other Hardware Motors, Mechanics, Power and CNC
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Hey, I recently got a sparkfun PWM shield ( SparkFun PWM Shield - DEV-10615 - SparkFun Electronics ) with the purpose of controlling a lot of servo motors (TLC5940).
The first problem I have is that I can only get the servo to turn 90 degrees when using this TLC5940 shield. I use the TLC5940 library along with the tlc_servos library.
The servos are capable of turning 180 degrees (without the TLC5940), so the problem is not with them. I have not used TLC5940 before so I guess I do something wrong, anyone knows?
I guess it may have something to do with what the first comment on sparkfun's product page mentions, but Im not sure what to make of it:

"HMMMM. It’s worth noting that the signal you get from using this with the Arduino library might not be what you expect. As a constant current sink, this chip will generate a LOWER duty cycle as the value is increased in the code. Applying a value of 4096 will turn it into ESSENTIALLY an open drain. Sending 1 will make it have almost a 100% duty cycle. This can be addressed in code easily by mapping 0,4096,4096,0 etc, but should be remembered. You can also throw a hex inverter in between this unit and your target if you’re looking to JUST generate pulses and constant current is unimportant."

The other problem makes me feel more stupid, but I'm not entirely sure how to power the arduino with this shield on.
In the past I've used external power for servos and a 9V battery for the Arduino, and tried to do it that way now too by using the 9V for the arduino and then 4.8V through the inputs of the shield for the servos (it has a switch for 4.8V or Vcc).
But for some reason it doesn't seem to power the arduino this way. It works with USB + external 4.8V for servos, but whenever I free the ARduino from the USB and use the 9V it won't run (it lights up, and the servos are getting power, but it won't run. Perhaps it gets the 4.8V instead of the 9V and is underpowered somehow?) [semi solved, see edit 1-3]

I'm thankful for any ideas :slight_smile:

Edit:
I guess it might be that I should power the Arduino completely through the shield, and there fore need more power thorugh it. Maybe then set the switch to 5V, maybe it just limits the voltage to the pins and not to the arduino? I'm not sure whether I will fry something or not but I'll give it a shot with one servo :stuck_out_tongue:

Edit 2:
Yap, more voltage to the shield Vin seems to fix the problem with power.

Edit 3:
Or so I thought, it dies after a short while.

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Hey, I recently got a sparkfun PWM shield ( SparkFun PWM Shield - DEV-10615 - SparkFun Electronics ) with the purpose of controlling a lot of servo motors (TLC5940).

Where in the link does it say that shield is for use with servos?

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Second paragraph

Use this board to increase the number of PWM pins available to your microcontroller for applications such as monocolor, multicolor or full-color LED displays, LED signboards, display backlighting, servo control, or any other project where a large number of PWM drivers are necessary.

I actually happened upon it after reading this

http://bildr.org/2012/03/servos-tlc5940-arduino/

But that breakout board wasn't easily available here in Sweden so I ended up with the shield instead. Should probably have gone with an arduino mega from the beginning I guess...

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A lynxmotion ssc-32 servo controller controls 32 servos and attaches easily to an arduino (but not a shield). The ssc-32 is ~$40 in the US. It might be worth a look (might also simplify the arduino programming).