I am trying to make an accurate small fishing reel for Halloween the problem is getting it to return to exact points of origin
I was thinking an absolute encoder servo would be the right approach but I don’t want to spend a ton of money since it doesn’t need to be strong just take up 30’ of fishing line
An absolute encoder would require a gear train since I’m pretty sure your fishing reel would have to make more than one complete rotation to take in 30’ of line. An incremental encoder would easily work in this application. Another possibility would be to use limit switches. You would have to attach something small to the fishing line in order to trip them, like a tiny sinker.
-Bill
I honestly am considering using two lines so an object can retract across the grass and then back to the end of the pole so I don’t think the limit switches would give me enough freedom and yes the reel needs to be able to do 120rev
Sounds like an old fashioned clothesline reel’n’pulley, driven by a DC motor would work. A simple switch that closes once per rev should be close enough for positioning. Just keep count of the switch “clicks”. A good project to be Arduinofied.
Instead of counting reel revolutions, it’s probably much easier to detect when the “object” is at the ends of its travel.
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Come to think of, there are any number of scenarios where counting is an easier solution than a limit switch.
http://www.specialist-wire-rigs.co.uk/camera.shtml
Maybe these ideas will get my point across better . I don’t want to achieve the same locations every time i am sure that I will probably have three motors after all but was trying minimize
WRT the only question you’ve specifically asked … I still hold that you don’t need an absolute encoder, simply counting the rotations (or fractions thereof, if truly needed) is sufficient. Especially if this is for some active Halloween display. Take end position counts at the … ends … of each of the 3 reels you’ve mentioned and I think it a simple calculation to determine the counts from each home to any position. I suspect it’ll be some combination of a look-up table and interpolation. I think the mechanical design challenges outweigh the electrical and software ones.
