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Building an optical encoder

Building an optical encoder

A simple and inexpensive method of constructing a robust optical encoder capable of producing quadrature encoded signals.

A conventional panel-mount potentiometer was used as the basis of the mechanical housing. This is shown in Figure 2. This device eases the mounting arrangements, since a threaded sleeve is already built in, and it also provides a stable platform on which to attach a control knob. Trying to mount the soft plastic wheel to a front panel, and then fit a knob to the thin shaft would have otherwise been almost impossible.


Since this device is just the encoder, additional parts are required to produce usable quadrature encoded signals. A typical circuit is shown below. This circuit is one I have used when building a direct digital synthesizer. The synthesizer included a Lock button which prevented the frequency from being changed inadvertently – hence the enable switch on the transmitter LED.

Article by Steven J. Merrifield at

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