ELM408 データシートの表示（PDF） - Elm Electronics

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ELM408

Rotary Decoder - 2 wire Interface

Elm Electronics 

ELM408

Example Application

Figure 11 below shows one example of how the

ELM408 might be used with a digital potentiometer (in

this case, a Microchip Technology MCP4011).

Pullup resistors of 10 KΩ are used with the rotary

encoder to provide voltages for the A and B inputs of

the ELM408. Power is supplied from a common source

that we’ve simply labelled VDD (it should be between

2.7V and 5.5V for the MCP4011), and a small

capacitor has been added to ensure that the supply is

filtered. The MCP4011 data sheet recommends using

a 0.1 µF capacitor, so if this is physically very close to

the ELM408, you might be able to eliminate the

0.01 µF one

Pins 4 and 5 of the ELM408 have been connected

to circuit common (VSS) which means that the outputs

will appear as in Figures 4 and 5, and that we are

using 2x decoding. The ELM408 output lines are

directly connected to the MCP4011 inputs, and we

have added a 10 kΩ pullup resistor on the CS line to

ensure that the voltage rises as quickly as possible

after power on.

That’s about all there is to using the ELM408.

Connect pullup resistors to your rotary encoder,

connect the encoder signals to the ELM408, then

connect the ELM408 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!

10 KΩ

VDD

10 KΩ

VDD

0.01µF

1

2

3

A

B

4

rotary

encoder

C

VDD

8

10 KΩ

7

6

5

VDD

0.1µF

1

2

3

4

8

MCP

4011 7

6

H

L

W

5

Figure 11. Connecting the ELM408 to a MCP4011

ELM408DSA

Elm Electronics – Circuits for the Hobbyist

www.elmelectronics.com

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