So what I want is a system that when tension is put on the rope/what ever, it feeds out. But when I stop pulling, it stops feeding.
So I need a sensor with a spring which detects the tension, a brake mechanisum and something else.
The sensor has springs and is "in the middle" (as drawn) at neutral.
If I pull it moves to the right and the brake is released.
When I stop pulling, the sensor moves to the left and the brake is re-applied to stop it un-spooling.
The problem is the brake mechanisum wearing out too quickly.
And sorry for the spelling mistake on the picture. I am not running on all cylenders. (see?)
P.S.
What I am also thinking, instead of just "free wheeling" a servo motor is used to control the reel.
As I pull and the sensor detects tension it makes the servo turn. If I stop pulling, the sensor detects it and stops the servo feeding out.
Off the top of my head, the sensor could simply be the lever on a microswitch- read the switch to decide what to do.
Then using an h-bridge for the motor you can handle the direction and (if I understand these things correctly) also brake the motor electrically rather than using a mechanical brake-shoe kind of arrangement. But I have no idea what kind of breaking force can be applied electrically....
That would spool the reel at "speed x" irrespective of how fast I pull. Yeah, as the switch re-centers it would turn off the motor, then as it tensions again, turn the motor on again.
I was thinking an analogue sensor and the faster I pull, the faster it spools.
When I stop pulling, the sensor moves to the left and the brake is re-applied to stop it un-spooling.
The problem is the brake mechanisum wearing out too quickly
What brake mechanism are you using?
What is the maximum weight of your reel when full?
How quickly does the thing need to stop turning?
The mechanism is unknown yet. It is conceptual.
Weight, about 2 kg
Speed? Well, 2 meters/second. Maybe spikes to 6.
Quick enough that there isn't a "bow"/loop formed under and the rope de-spools so when I next pull it, it isn't wrapped around the axle.
lost_and_confused:
The problem is the brake mechanisum wearing out too quickly.
A simple friction brake seems like the obvious solution here. Does your comment above imply that you've got this working? Because I'd have thought that brake wear issues would be far easier to address than creating a new powered spool mechanism. If you plan to start/stop winding abruptly then it might help to loop the rope round a sprung pulley so that the main pulley does not have to instantaneously match changes in the unspooling speed.
Think about running the wire/cable/string/rope through 3 pulleys. the 2 outer ones are fixed and the one in the middle is on a spring loaded arm and floats, depending on cable tension. You connect that to a potentiometer or several switches. one switch for tight, one for feeding nicely, and 1 for way loose. When the cable tight is on the cable can be fed. WHen the cable is in the feeding nicely position you can stop the motor until cable tight, and on cable loose you wind in the cable. with a potentiometer you could use the position to control the feed in and out so you could control the tension.
If you use a gear head motor with a worm gear (e.g. windshield wiper motor) you would not need any kind of brake. You would still be able to power feed in either direction.
