Electronics > Beginners
Ideas for PCB sprocket for PNP?
(1/1)
shai:
I am building a PnP Machine and would like to create the sprocket for my feeder out of PCB. See attached. This sprocket will NOT push the tape, only count steps.
I know that PCB is not the best material for a sprocket, etc, etc. I would like to focus on one thing only - how to create a good and cheap encoder for this sprocket. I have a few ideas but perhaps someone with more experience can tell me what would work best and if you have better idea to share?
Ideas:
1. Drill holes in sprocket and use optical sensor (self explanatory, but I'm afraid this is not very super accurate for PCB material)
2. Use two springs that will contact with each pad. Simplest way to do it, just the cycle count might not be high as the sprocket/spring could wear out from physical contact/rotation.
3. Use optical encoder that reflects off the pads and make sure the PCB is matte black. (will this work? or will it still reflect off a matte black pcb?)
4. Use a Hall effect or similar sensor and detect the pads. (This one I'm not sure, non-lead-free pads? is that a possibility? Can any sort of SMT pad coating type be detectable with a Hall effect sensor? I think they are cheaper than optical encoders? Suggestions here?
5. Any other ideas on how to get creative with a PCB sprocket to be used as encoder?
https://imgur.com/a/2t7MSwc
https://imgur.com/a/cnNVQra
ataradov:
Just a thought, not a specific advice - PCB holes are as accurate as alignment of the copper layer. It should be plenty accurate for this use.
For solder mask reflection, you are probably better off using just plain openings in the mask and no copper. You will get contrasting color between the mask and PCB material. But mask alignment may be much worse than alignment for the holes.
With spring contacts - what do you plan to use for the actual contacts? I'm not aware of anything like that sold as a generic component.
Also, what sort of resolution do you expect, and what is the size of the wheel?
shai:
The sprocket is 26.4 diameter (not pitch), just measured the diameter itself without teeth. Holes can work, but I think I can get better step resolution with pads. What if I use raw FR4 and no solder mask and only pads? I don't fully understand what you mean in your second bullet point.
Springs: https://www.digikey.com/products/en/connectors-interconnects/rectangular-connectors-spring-loaded/408?k=&pkeyword=&sv=0&pv7=2&sf=0&FV=1140003%2Cii2%7C2167%2Cii1%7C2172%2Cffe00198%2C1f140000&quantity=&ColumnSort=1000011&page=1&stock=1&pageSize=500
ataradov:
Those springs look like they would be too hard, they are designed for permanent contact, not for sliding.
I mean use black solder mask, but don't put any copper in the openings, just keep bare PCB material. It is pretty light in color.
Navigation
[0] Message Index
Go to full version