Sensing Position

General project help for Adafruit customers

Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.
Locked
jmccormac001
 
Posts: 2
Joined: Tue Apr 22, 2014 6:36 am

Sensing Position

Post by jmccormac001 »

Hi,
(Sorry if this appears twice, I could not see my original post)
I am new to tinkering with electronics and have a small project I would like to do. It is similar to Lesson 12 on Sensing movement (https://learn.adafruit.com/adafruits-ra ... t/overview) but I am not sure the door sensors in the tutorial will give me the type of results I need.

Problem:
I have a slowly rotating metal disk and I would like to sense when it reaches a certain position (1 position only). I would like to know this position with a fair amount of accuracy (to within a degree or so if possible). Using the door sensors in the tutorial I am not sure I can achieve this type of precision. Would it be be possible to place a hall sensor (like this one https://www.adafruit.com/products/158) close to the rotating disk and a strong magnet (like this one https://www.adafruit.com/products/9) on the disk and use a similar set up to Tutorial 12 (pi, cobbler, breadboard etc) to tell when the sensor senses the magnetic field? If so would I need any extra components for the hall sensor? I'm not interested in the PIR sensor for this project.

Cheers
James

User avatar
adafruit_support_bill
 
Posts: 88089
Joined: Sat Feb 07, 2009 10:11 am

Re: Sensing Position

Post by adafruit_support_bill »

A hall sensor could work. Photo-interruptors or "slot sensors" tend to be more precise.

Image

jmccormac001
 
Posts: 2
Joined: Tue Apr 22, 2014 6:36 am

Re: Sensing Position

Post by jmccormac001 »

Thanks for the quick reply. Do you guys sell those type of sensors? I would like to place an order asap for a Pi and all the kit necessary to complete my project. I see this kit comes with pretty much everything I would need (https://www.adafruit.com/product/1014) apart from the sensors (and any additional equipment that might be needed to run the sensors).

In work we have these hall sensors (http://uk.rs-online.com/web/p/products/0307446/) they are similar to the one sold here. I actually need to measure the position of two discs from the same Pi. Would it be possible to run these from the pins on the Pi or would I need a separate 5v psu?

Thanks
James

User avatar
adafruit_support_bill
 
Posts: 88089
Joined: Sat Feb 07, 2009 10:11 am

Re: Sensing Position

Post by adafruit_support_bill »

We do not carry the slot sensors. If you have all sensors on hand, you could try those first to see if they can achieve the resolution you need.

You should be able to power it from the 5 pin of the Pi. But use a voltage divider on the output to scale the signal to 3.3v for the GPIO pin.

Locked
Please be positive and constructive with your questions and comments.

Return to “General Project help”