HalcyonKnights t1_itpx98g wrote on October 25, 2022 at 1:25 PM

Make your measuring "pulley" more of a flat-sided barrel and wrap the thread around it a few times before it goes onto the spool. That will maximize the friction and keep it moving, but keep the thread on a single layer where the diameter wont change your measurement. If you are 3D printing (or even if not) you can get really cheap skateboard bearings that you can put into the design too if you need to, especially if it's thin thread that ends up breaking on you. A separate, adjustable tensioner (spring or weighted, maybe) would probably be a good idea too.

Dabrush OP t1_itpygwq wrote on October 25, 2022 at 1:34 PM

This does sound like a relatively safe idea, now I'd just have to find a good way to count the rotations of that barrel, or ideally just give out the total spooled length directly.

Angdrambor t1_itq6j57 wrote on October 25, 2022 at 2:32 PM

Just buy a Measuring Wheel and skip building your own mechanisms. It's designed to be rolled over the ground for long distances, but there's no reason you can't use it to measure thread rolling over the wheel.

If your string keeps falling off the wheel, you can glue cardboard guides to keep it in line.

HalcyonKnights t1_itpzrlf wrote on October 25, 2022 at 1:44 PM

I would not try to reinvent that Wheel (unless you want to spend more time and money on the learning experience).

Mechanical (Rotating Shaft): https://www.amazon.com/Mechanical-Counter-0-999999-Resettable-Accurately/dp/B0975Y79RF/

Mechanical (Paddle Whack method): https://www.amazon.com/KTRIO-Counter-Handheld-Clicker-Mechanical/dp/B075QFK6DG/

Electronic: https://www.amazon.com/DIGITEN-Digital-0-99999-Proximity-Magnetic/dp/B01DNLRAUA

Gubguls t1_itr3j2h wrote on October 25, 2022 at 6:07 PM

I don’t think that’s the type of sensor he needs. Something like the rotary encoder as was suggested.

SuperbLlamas t1_itqjqeq wrote on October 25, 2022 at 3:59 PM

Rotary encoder is how I’ve done something similar in the past.