Example Application

4 of 4

Figure 1. Manual Control of a Stepper Motor

Figure 1 shows the ELM410 used to interface two

momentary action normally open pushbutton switches to

an ELM310 in a manually controlled stepping motor

circuit. For simplicity, the stepper motor and its drive

transistors are not shown on this diagram.

Using the ELM310 to control a stepper motor has

many advantages - low cost, low power, ease of use,

etc. There is one disavantage however, in that the

integrated circuit is capable of responding quite quickly

to inputs. This would result in multiple steps of the

motor, and perceived erratic operation, if the input were

connected directly to a switch, and not debounced by a

circuit such as the ELM410.

The circuit below shows how easily two control

switches can be debounced and used to control the

ELM310. The two switches are simply connected

internal pullup resistors to detect the state of the switch.

Power is obtained from the circuit being connected to,

providing the correct logic drive levels. Finally, the

unused

debounce

circuit

is

simply

left

with

no

connection to it. This is acceptable in this case, as the

internal pullup resistor will prevent the input to circuit 3

from floating.

Another variation on this circuit would have been to

invert the direction control input by connecting pin 3 to

pin 4 on the ELM410, then use pin 5 to drive pin 3 of the

ELM310. This would have resulted in the direction

pushbutton causing a counter-clockwise rotation when

pressed due to the double inversion from the two

debounce circuits connected in series.

For more permanent installations, consideration

should be given to protecting the ELM410 from

electrostatic discharges, etc. by providing series current

limiting resistors, and additional pullup resistors. For

typical useage in prototyping and experimenter circuits,

however, nothing more than is shown below would

normally be required.

ELM410

ELM410DSB

Elm Electronics – Circuits for the Hobbyist

< http://www.elmelectronics.com/ >

2

3

4

7

6

5

1

2

3

4

8

7

6

5

+5V

8

1

0.1µF

+5V

A

B

C

D

To winding

drive circuits

Step

Clockwise