speed control

it would be cool if you could somehow program the motors to go at different speeds (ex: 1, 2, 3), and especially if you could do this through the remote without programming. While gearing ratios can care for this, being able to drastically change speeds without reconfiguring the robot would be great.


This is what the sticks do, move them a little and you go slow. Move them a lot and you go faster.

If you want to change the torque or top speed, you’ll need a transmission. Or bigger/better motors and a real speed controller (which I thought your post was about).

sorry 'bout the confusion. Yeah, but the thing about the sticks is just so… inacurate. You have to be super careful with that, and if you move it just a hair too much, then you ruin your delicate operations.

that, and the fact that this doesn’t always work…especially with terrain differences. (carpet and texture-tile wreak major havoc on this…).

I was also kind of hoping for a VERY large range of speeds… snail-racecar, you know?

Look up scaling in the inventors guide if you want more accurate sticks

when you want more speed for any movement (arm, wheels, claws, etc.), do not use any gears with the motors you utilise for your robot.

I know what you mean about them being inacurate. We got fed up with it because robot physical changes didn’t really help the problem so we put the contoller on our oscilliscope. It showed that there are only 50 steps of position sensing from the bottom to the top. Most standard RC controllers are at least double this.

That does bring up an interesting variation of this idea…

The existing Vex motors are not speed regulated. In other words, the joystick setting controls how much power the motors get. As you point out, that can result in a variety of speeds, depending on conditions. If you want the joystick to control motor speed, then you have to use a shaft encoder to read the current speed and adjust motor power to match.

Now for the idea part: It would be great if Vex had a speed-regulated motor that took the control signal as a speed setting rather than a power setting. It would self-adjusted power to try to achieve the target speed. Obviously, if it gets bogged down, it’ll go slower than you want. But at the lower-end of the speed range, it should provide much more consistent control.

Just a thought…

  • Dean

If those encoders were build into the motor they will be extremly useful for all sorts of things and would be way more accurate than what we have now. It wouldn’t be too hard for them to do it. The same motors are sold elswhere with encoders alerady in them. Vex just takes them out for their products.

Built-in encoders is one thing (and would be great!). But I’m talking about taking it one step further and having the motor self-regulate it’s speed based on encoder feedback. Kind of like the way the servos self-regulate their position based on the potentiometer feedback.

  • Dean

I got what you said, I was just pointing out the added bonus of having encoders in the system. We could do sooooo much more with autonomous especially if the motors did smoother self regulating at low speeds.

i absolutely love where this is going. One thing that i would like to see, just as a decoration thing, is to have a LED bar feedback on the controller… 1=slow, 2=sortof slow, 12=fast…

if you mean the microcontroller, it’s kinda gimmicky, and for competition robots (at least mine) it is hard to see. If you mean the controller, if you have to look at the controller to drive, I would say you need more practice.