Figure 4 below shows how the ELM401 might be

used with a microprocessor. Power for the ELM401

has been obtained from the microprocessor circuit,

and a small capacitor has been added to ensure that

the supply is filtered. The positive supply has been

with any voltage from 2.0 to 5.5 volts.

The circuit uses 10 K

Ω pullup resistors with the

rotary encoder signals in order to convert the signal

encoder is treated no differently than the ones from the

encoder wheel. Since both ICs share the same supply,

they can be directly connected as shown.

That’s about all there is to using the ELM401 in

your circuit. Connect pullup resistors to your rotary

encoder signals, connect the encoder signals to the

ELM401, then connect the ELM401 to the controlled

circuit. Use a common supply for all the devices, and

add a small bypass capacitor across the supply line.

The

controlled

devices

can

be

digital

pots,

microprocessors, or almost any circuit that will accept

CMOS signals. Enjoy!

Example Application

8 of 8

ELM401DSB

Elm Electronics – Circuits for the Hobbyist

www.elmelectronics.com

ELM401

Figure 4. Connecting the ELM401 to a microprocessor

0.01µF

your microprocessor

port pins

1

2

3

4

8

7

6

5

10 K

Ω

10 K

Ω

A

B

rotary

encoder

C

Sw

10 K

Ω