Rotary Decoder – 3 wire 2x Interface


Quantity Pricing

The following are the unit prices, as you vary the quantity purchased:






All prices are in Canadian dollars. We use the total number purchased (ELM404P + ELM404SM) for the calculation.


The ELM404 is an 8 pin integrated circuit that is used to convert the output from a rotary encoder into three signals (chip select, clock and up/down) that can be used to control various devices. The low power CMOS technology used ensures that only a very small current is required over the entire 2.0 to 5.5 volt operating range.

There is no need for external filtering or debounce circuits with the ELM404, as this is all performed within the integrated circuit. After debouncing the encoder signals, the ELM404 determines the direction of shaft rotation, and then generates the appropriate outputs. The polarity of the clock output can be changed at any time to accommodate different needs.

The ELM404 provides 2x decoding of a rotary encoder signal. If your application requires 4x decoding, please see the ELM405 (it is identical to the ELM404 in every respect, except that it provides 4x decoding).


  • Digital audio potentiometer controls
  • Variable voltage or temperature circuits
  • Positioning controls
  • Tuning circuits


  • Low power CMOS design
  • Wide supply range – 2.0 to 5.5 volts
  • Complete debouncing of the encoder inputs
  • No external filtering needed
  • 2x decoding
  • Startup delay timer
  • High current drive outputs

Connection Diagram

( PDIP or SOIC, top view )
ELM404 connection diagram