
Troop191Robotics
USA
Asked
— Edited
I can control my servos, forward and reverse with the SMP. However, I can only drive them forward with the Horiz servo or Vert Servo.
Any ideas?
Thanks again
Please provide more detail to your question so we can help you
I have a lot of VEX parts that I spent a fortune on. I am trying to help these guys complete their robotics project by giving them some of my parts, since I have parts but not cash. Hmmmmm.
Is there a way to stretch that reverse pulse width by a command?
Thanks again
Every control has a CONFIG button which opens a config window. Within the Modified servo config, you will find values to configure for each direction of both channels (left and right). The values are Forward, Reverse and Stop. A checkbox will send a PWM for STOP rather than sending no PWM (which is default).
Use the values in the CONFIG menu to select values that work for your hardware.
I don't think it is really an issue with the EZ-B so much as the semi-proprietary nature of the VEX components.
With regards to what you might be running into, I did read somewhere the the VEX servos & motors (with their controller adapter) have a higher voltage range of 5.5 - 9 volts and thus may not work well with typical servo controllers without first supplying external voltage to the motor and running just the signal wire to the controller (and common ground between controller and servo power)... try that with your setup.
As to the operating voltage for the VEX motor controller, I am using a regulated 8 Vdc. Thanks, that's important. I monitor it with a panel meter. it is well behaved.
Thanks guys
Anyway, I just ran into the same issue when I tried to drive my Fergelli linear actuator in the servo mode. It would not reverse. So, I ran it in the PWM mode.
Just some more info
Try playing around with the PWM and then possibly running your VEX servos using a scripted preset PWM setting and see if you can control them that way.
Disclaimer... I am really pulling this one out of my... hat
@DJ, when I am playing around with the modified servo control and watching the scope, I do not see any changes when adjusting the config values... what are they supposed to do in this particular control?
Just to be clear, that trick of switching to PWM worked for the Fergelli, since it has a built in motor controller withe 5 different modes of operation. The servos do not have that luxury. I ran them from a horizontal, and vertical servo script. That works. It is just from the Modified servo mode that I had no success.
We'll get there
Thanks!
I test things using the sliders and when they work, I write script commands to execute them.
I used the PWM slider to drive my linear actuators. I monitored the waveform from the EZ-B and the dc voltage that was delivered to the linear actuator. All was in order.
Then I wrote script commands to do the same thing. PWM(D2, 0) for example. I saw a constant high, 100% duty, from port D2. It did not modulate the duty cycle, like the PWM slider did. So, of course it would drive the linear actuator to its stop and not come back. I can still control it properly from the PWM slider.
Any ideas?
I am sure you know this, but just in case... the script setting you used would lock the PWM at a single setting (like leaving the slider stationary in one spot)... you would need to change the position value to a variable and have some input adjusting that variable in a loop to act like a slider does.
Stop me now if you already know all that