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Get speed from peristaltic pump, add magnet and hall effect?
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rhodges:
I am working with small and cheap peristaltic pumps. The goal is to feed oil slowly into a burner. My PWM is working, but it is open loop. I really would like to get the pump speed.

I am open to all ideas. Right now, I am thinking of adding a magnet to a pump roller with a hall effect device on the outside. In the pictures, you can see that the magnet is very small compared to the roller. I would drill a shallow hole in the roller for the magnet and trim down the post that holds the roller.

Thanks!
Conrad Hoffman:
Magnet and hall effect is a common way to sense. There are some rotary hall effect sensors you could put on the end of the motor shaft.
https://www.allegromicro.com/en/Insights-and-Innovations/Technical-Documents/Hall-Effect-Sensor-IC-Publications/Advanced-On-Chip-Linearization-A1332-Angle-Sensor-IC
OM222O:
I think optical encoders are cheaper than magnetic counterparts and you can get them in really thin packages too  ???
jbb:

--- Quote from: rhodges on August 20, 2019, 02:16:07 pm ---The goal is to feed oil slowly into a burner. My PWM is working, but it is open loop. I really would like to get the pump speed.

--- End quote ---

If you can live with a slow update, then magnet + Hall effect sensor is simple and effective and should be quite forgiving on alignment, dust and grease. But it'll only update once a turn, so it won't allow for fast, smooth control of the pump motion.  You'll be able to gradually adjust the PWM to get a constant speed over the course of a few turns.

If you want to enable fast & smooth control with a response time in less than a few turns, then a higher resolution encoder is required as others have suggested.
CM800:

--- Quote from: OM222O on August 20, 2019, 07:47:30 pm ---I think optical encoders are cheaper than magnetic counterparts and you can get them in really thin packages too  ???


--- End quote ---

... really? That's news to me! I'd love to find low cost optical encoders!

http://www.hobbytronics.co.uk/magnetic-encoder-kit

or one of the many on-axis magnetic encoder chips (a personal favourite)
https://www.allegromicro.com/en/Products/Sense/Linear-and-Angular-Position/Angular-Position-Sensor-ICs.aspx

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