I am using a 12 and a 24 channel maestro controller to operate the many servos of an automaton using LabView software. So far the project is going well, these controller boards are great. Now I want to use several channels to control LEDs. I know that I could get on/off control by configuring channels for digital output but I want control of the brightness please.
One solution is to use a small servo to vary a potentiometer (varying the supply voltage to the LED) but this seems clunky, this would give me brightness control and speed of change of brightness. Does anyone know of a circuit that would use the servo ouput waveform to light an LED, so that I can vary the LED brightness keep the channel as a SERVO channel? I am looking for a simple circuit if possible as I will need several of then, perhaps 10 or 12. Thanks for an suggestions and happy new year to POLOLU community.
You can use the PWM output feature of the Mini Maestros to control the brightness of one LED. See the “Set PWM” command in the “Serial Servo Commands” section of the Maestro User’s Guide:
This feature does not have acceleration or speed limits so you would need to send a stream of Set PWM commands from LabView to get fading effects. This feature is not available on the 6-channel Micro Maestro.
–David
Yes, I understand your reply but I am trying to control the brightness of several LEDs independently. If anyone knows of a circuit that would accept normal maestro servo output to control brightness of an LED, I would be grateful. Thanks 
Finally found a great solution to my need to control separately the brightness of several LEDs from my maestro mini 24. I found this great site where somebody had done what I need.
zerorc.com/how-build-servo-led-driver
This morning, I tried it myself and it works a treat. Basically, I keep the LED control channels configured as SERVO outputs. Then modify a cheap servo, disconnecting the pot and replacing with a 2 resistor network (same as the modification for continuous rotation motion),discard all the gears and motor, then connect an LED (with series resistor to limit current as per LED spec) in place of the motor. I modded a TowerPro SG90 and it was easy. Now I have brightness control with speed of change of brightness.
Hello,
Did you consider any of the LED driver products from Mactech listed in our LED category? For example, the OctoBrite can control 24 channels for much less than the cost of 24 servos. These products do not use servo pulse signals, but they can be controlled by a Mini Maestro.
-Paul
Paul,
Yes, just checked out the spec of the OCTOBRITE and it looks good, although 20mA max per channel seems too low for my requirement. Also, I live in the United Kingdom and have just checked the websites of all 8 of the listed distributors and none seem to carry it, although I guess I could order it from you direct.
Regards,
Gordon
Hello,
Did you also look at the ShiftBar? What LEDs are you trying to drive?
Anyway, if you call your preferred local distributors and let them know that you are interested in these products, they might be able to help you place an order or start stocking them in the future. But yes, you can definitely just order directly from us.
-Paul
Yes, looked at shiftbar, interesting but not for my current project.
I don’t know the make of my LEDs but know that some of my bright white ones take 50ma and some others I am using take 30ma.
But hey, my LabView code is running well and your Maestro mini 24s ability to internally do the intermediate outputs when I ask for slow changes of LED brightness (and servo positions) means I think I will keep with the hacked servo method. ( I know it sounds terrible to be “destroying” perfectly good $2 servos for each LED brightness channel but: what price progress?)
Thanks for your input to this thread Paul.
Regards,
Gordon
Hello,
Three $2 servos are still cheaper than a single ShiftBar, so as long as you do not need the precise control or features of the ShiftBar, that is not a terrible way to do it.
Good luck with your project!
-Paul