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I outline seven different techniques to measure the length of a telescoping EMT conduit pole, and demonstrate a photoresistor-based method.

This article is part of a series discussing methods for adding sensing capabilities to a DIY telescoping pole project made from EMT conduit. This article presents:

Seven different methods for sensing the extension length of a telescoping pole made from EMT conduit!
An in-depth look at the photoresistor-based technique among that list of methods.

While the extended length of a telescoping pole can be simply measured using a tape measure, a system for continuously taking such measurements is useful for many different telescoping pole applications and projects:

- Know if the pole has slipped
- Set a repeatable length (e.g. deployable fruit picker)
- Flagpole height measurement, at full mast, half mast, or anywhere in-between
- Set the height of an archery or hunting target
- Use the telescoping pole itself as a measuring stick
- And more!

This article will show you how to add extension-sensing to an EMT conduit telescoping pole by utilizing low-cost, off-the-shelf components:

- EMT conduit telescoping coupling
- 1”, 3/4”, and 1/2” EMT conduit from your local hardware store
- Photoresistor/light dependent resistor (LDR)
- An Arduino microcontroller
- And some additional electronics!”

Link to article