Ideas

hello just want to no other peoples suggestions.
wich do you think is easier and/or effecive: having encoders on 4 arm motors to count revolutions or having an encoder on a shaft that connect both side together?:confused:

I’m confused on what the options are. I would connect the encoder to something that is connected directly to the shaft controlling the arm though. If you have it on a shaft such as an idler gear or on the motor and you lift your arm or lower it, that gear can skip if enough stress is put on it which would cause the arm heights to get messed up by this. Our team had trim on the robot saying if lift encoder < 50 then we want the lift to go down, but it messed up and the lift would always go up when we want it to go down because it would skip gears if we lowered the arm too far.

Long story short: have the encoder connected directly to the arm shaft somehow, whether having a secondary chain connecting the encoder and arm or attaching encoder straight to the arm.

If all four motors are supposed to be going at the same rate, the four motor encoders on the motors would be a bit redundant. One IME would probably do if you have mechanical synchronization as it sounds.

IME may be easier to fit than the external encoder, however given I2C reset issues, you may not have absolute position upon resets. However if you you use a regular encoder you start at 0 at reset there too so equally bad.

Is the motion too much to have a potentiometer? Those are absolute reads of resistance at rotational position which a power reset does not effect. However it is only 270 degrees of movement. The resistance is always the same (nearly, they can shift about slightly if not tightened down enough so the floor may be a bit above or below the original target)

We originally had IME’s on our lift and the continued to cause problems with disconnecting and the like… We ended up switching to regular encoders to eliminate the issues. We used a limit switch at the floor position of the lift to reset the encoder every time that the switch was activated. On startup the robot runs the lift down until the switch is triggered. When the switch is triggered the encoder value is reset to 0. This gets rid of any cumulative error in the encoder and ensures that you start the match with the lift at the correct position.

hope this helps!
:smiley:

My team uses potentiometers for absolute precision, but if you use IME’s keep in mind that the 393 Encoders have been out of stock for a long time now. I wouldn’t use them without a spare set of gears.

I wouldn’t use them with a 10 foot pole :wink:

I wouldn’t touch them either. Connect the sides so there is no way that they can be different and use one quad encoder. This will simplify programming and will be much more reliable.

We just stuck a 60 tooth gear nehind the wheel and then had a 60 tooth gear going to the encoder so we could keep both the motor and encoder on the inside of the frame. It worked great all season so our new bot is done the same way.