PWM signal driver theory

[Adama]

What exactly does this thing do?

http://www.vexrobotics.com/pwm-driver.html

I am trying to run Victor 884 off of a non-IFI controller. Can I feed the driver a varying voltage from an analogue output? What sort of input does the driver need?

In my collective 8 years as a high school student and now graduating college student I have never bothered to do anything with FIRST supplied controls and I am feeling quite child like at the moment.

Thanks for you help guys.

[Kevin Sevcik]

It's a signal booster. The Victor 884s draw more current on the PWM pin than your standard hobby servo and want nice sharp transitions besides. All the signal driver does is run your incoming PWM signal through some circuitry that spits out the same signal, only with more current drive behind it. So the signal into and out of it is the usual hobby-style servo PWM, but the output signal has better drive circuitry behind it that the Victor with be happier with.

[Adama]

So then I will still need to generate a PWM signal at the controller before I pass it through the cable?

Well, it wasn't exactly the answer I was looking for but I appreciate the help.

This leads to a new question. With out specific knowledge of the controller being used, is there a drop in module or easy to execute way to turn turn an analogue signal into a PWM signal?

[Tom Bottiglieri]

You should be able to generate a compatible signal from most any microcontroller. What type of controller are you using? You just need to make it look like this.

[Adama]

http://cn.siemens.com/cms/cn/English...ompact/1en.pdf

Its hideously too much for what we are doing but another member of the group was able to borrow one from work for the duration of the project. And presumably knows how or knows someone who can use it. He is looking into making it output PWM signals at an acceptable rate.

We were hoping to just use one of the analog outputs as he is still kinda fuzzy on the operation of the DO's.

[Kevin Sevcik]

Wheeeee... I think you're out of luck for PWM output on that PLC. The digital outputs on that are relays, which aren't likely to switch quickly enough. And are likely to die a sudden death if you convince them to switch quickly enough. You'll definitely need to find some sort of analog->PWM converter, or find yourself a different controller.

If you have access to some FRC hardware, you might try the RobotOpen Arduino Shield. You'll need an FRC digital sidecar, power distribution board, and a few other things, but it's a heck of a lot more likely to work and work well FRC speed controllers and electronics.

[Adama]

Update:

Bought an Arduino Uno, Ran the servo calibration and the basic pot/servo control code. Works great.

Thanks for the input guys