Can Victors work as ESCs without all of the other electronic components?

[VEN]

Hi, i was wondering if a victor can be used as a speed controller without all the other mumbo jumbo electronics.

Thanks,


Vova

[AdamHeard]

Yes. The victor only cares about the pwm signal, it doesn't matter where it comes from. I've used Victors with vex controllers and RC car radios before.

[VEN]

just looking to put one on our FIRST mobile


Thanks!!!!

[VEN]

Ok, now question #2, how do I control the victor without wireless. I'm thinking an electric scooter throttle control but have no clue how to make that.

[jgannon]

To control a Victor, you'll need a circuit that can produce a pulse width of 1-2ms at a frequency of no more than 120Hz. I'm sure that this suggestion will make me unpopular with some EEs around here, but a simple 555 circuit will probably get the job done for you. Then you can use a potentiometer to vary the pulse width, and the whole thing shouldn't even cost you $10.

[Cody Carey]

Yeah, a 555 chip should get the job done. I recently stocked up on parts, and the 555 chips are down to about $1.69. Just check out RadioShack.

http://www.radioshack.com/family/ind...032058.2032230

[VEN]

Is it as easy as buying one of those circuits, attacing a pot to it, on the other end the pwm and to the victor?

[karlcswanson]

i don't think that would be to safe, if the duty cycle(i think that is what it is called) is below 50%, the motor will go backwards. you might want to use a small microcontroller for it, i would recommend an arduino, which is based off an ATmega8

[JBotAlan]

Originally Posted by VEN

Is it as easy as buying one of those circuits, attacing a pot to it, on the other end the pwm and to the victor?

I'm not entirely sure. This isn't how I'd do it; I'd put a robot controller and operator interface on there. That way, you can do a cool drive system like you would on the actual robot, and it would look way cooler. You don't need any radio communications at all; grab a tether cable, tether the two together, and fire away.

On a side note, please put a cutoff switch somewhere between the battery and motors that's easily accessible. A rampant "FIRSTmobile" could be a very scary thing...

JBot

[Justin M.]

RobotLogic sells something called the IMX-1, which acts as a PWM signal booster, which runs inline with a PWM cable to operate Victors with standard RC equipment. It also mixes signals for one-stick driving, and uses a spare RC channel for inverted controls, which is useful in combat robotics if you get flipped over (assuming your robot can drive inverted), or to make backwards driving easier.

http://www.robotlogic.com/product_imx1.html

[Dad1279]

Do a google search on 'servo tester'. It is a relatively simple circuit.


Also certain PIC type processors have PWM on board circuitry. Try a search also on PIC PWM.

[Andy A.]

If you choose to use a supplementry circuit to generate the PWM signal, be sure to familiarize your self with the calibration routine. It is likely that a custom circuit will not output values that match those the Victor expects from the IFI equipment. Calibration will force the victor to scale the values, allowing you to set neutral, reverse and forward to values the circuit can produce.

This also goes for anyone using a Victor with hobby R/C gear. The factory calibration makes the assumption of using a PC joystick and an IFI control system. With out those, the factory calibration isn't even close.

-Local

[jgannon]

Originally Posted by karlcswanson

if the duty cycle(i think that is what it is called) is below 50%, the motor will go backwards.

Are you sure about that? If you actually read the Victor 884 data sheet, it definitely sounds like you're supposed to send a 1-2ms pulse with a frequency no greater than 120Hz. A 2ms pulse should be full forward, even though that's substantially less than 50% duty.

Originally Posted by VEN

Is it as easy as buying one of those circuits, attacing a pot to it, on the other end the pwm and to the victor?

It's not quite that easy. You'll need a couple of capacitors and resistors, I'm sure. Search around for 555 circuits, or pick up a copy of Forest Mims' timers and op-amps notebook.

[Al Skierkiewicz]

You can find a wealth of info on the IFI FAQ for the Victors here...
http://www.ifirobotics.com/forum/vie...4742c7 8d25be

From that page...
Here are the required input control signal characteristics of the PWM input signal for the Victor and the PWM Outputs for our RC units:

Period for the Mini RC PWM Output: 17.0 ms.
Period for the FRC Robot Controller PWM Output: 26.2 ms.
Maximun Rate: 120 Hz.
Pulse width: 1 - 2 ms

As the positive pulse width varies from about 1 ms to 2 ms, the Victor will range from Full Reverse to Full Forward. The Victor should be in Neutral at about a 1.5 ms pulse width.

[John Gutmann]

Originally Posted by JBotAlan

I'm not entirely sure. This isn't how I'd do it; I'd put a robot controller and operator interface on there. That way, you can do a cool drive system like you would on the actual robot, and it would look way cooler. You don't need any radio communications at all; grab a tether cable, tether the two together, and fire away.

On a side note, please put a cutoff switch somewhere between the battery and motors that's easily accessible. A rampant "FIRSTmobile" could be a very scary thing...

JBot

Or....You can just have the robot controller on it if your going to go there route. I think all you need to do is set the team # to 0 or something like that. I have used the RC alone before, I just don't remember how I did it. I would say your better of spending 10$ on perfboard and a small microprocessor then just have somebody write code for you.

If you give more info on the project it would be easier to help. For example I can tell you to make an Hbridge, but I don't know if that would fit the project.

Or you can go to somewhere like pololu.com and buy there servo controller and buy a basic stamp and just use the serout command to send serial data to it. If you have the money for that i would say that would work just fine.