EYE on NPI – Bourns PEC11D Series Dual-Centric Rotary Encoder with Momentary Push Switch #EyeOnNPI
Channel: Adafruit Industries
Date: 15/03/2022

This week's EYE ON NPI is a gaze into the duality of man! Wait, no, it's a gaze into the dual-concentricity of this fascinating new rotary encoder: the Bourns PEC11D Series Dual-Centric Rotary Encoder with Momentary Push Switch (https://www.digikey.com/en/product-highlight/b/bourns/pec11d-series-dual-centric-rotary-encoder-with-momentary-push-switch).

We have covered rotary encoders and switches on EYE ON NPI before (https://blog.adafruit.com/?s=eye+on+npi+rotary) so you may be familiar with them.  Rotary encoders are a popular user interface element that engineers use to add a tactile increment/decrement control. We find they’re much more intuitive to use than touch screens, especially when you want to increase or decrease a value precisely: it's a lot easier to twist the knob by one detent than it is to press a touch screen once. Rotary encoders can also be used hands-free or when observing some output because the tactile feedback is strong.

The most common rotary encoders used for user input are mechanical style, usually with detents. They can be ring-style like the famous iPod Clickwheel or knob style. These are two mechanical rotary encoders in that there is a little leaf spring connected to the knob and the “common” pin, and the body has a metal-cutout piece, that when rotated connects and disconnects the two side pins from the common. The two pins pulse high and low to indicate motion and direction. Usually two interrupt pins are connected to the rotary encoder to catch the pulses and track the counter increment or decrement.

Say you have some product you're designing and you want to have two encoders in one, say because you want 'rough' and 'fine' adjustment. You could use one encoder and have the button state determine what mode the encoder is in. (https://github.com/adafruit/Adafruit_Learning_System_Guides/blob/main/Rotary_Trinkey/CircuitPython_ColorPicker_Example/code.py) However, there may be a situation where you want to use that button for entering the new setting. Or if you have a very space-constrained interface, and you can't fit two side-by-side.

That's where the Bourns PEC11D (https://www.digikey.com/short/013h5701) will come to the rescue! This encoder has two (count 'em two) rotary encoders in one package. By turning the outer or inner part separately you can control two electrically separated rotary encoders, and there's also a push-button input. You'll need to mould or machine a special knob to allow selection of either half, but most folks end up with custom knobs rather than off-the-shelf for a final product anyways.

We wired this cute li'l guy to an Arduino and ran a rotary encoder demo that was expecting two encoders and it worked like a breeze - just the way you expect! This unique user interface element definitely solves an existing problem and Bourns is famous for their high quality encoders, so you know it will last and work well in your product design. 

The Bourns PEC11D (https://www.digikey.com/short/013h5701) is in stock now for immediate shipment from Digi-Key. Order today and you'll be concentrically rotating by tomorrow afternoon!