ELM410
Example Application
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.
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.
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.
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.
The circuit below shows how easily two control
switches can be debounced and used to control the
ELM310. The two switches are simply connected
between VSS and their respective inputs, allowing the
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
A
+5V
1
2
3
4
8
7
6
5
To winding
drive circuits
B
C
D
0.1µF
5
6
7
8
4
3
2
1
Clockwise
+5V
Step
Figure 1. Manual Control of a Stepper Motor
ELM410DSB
Elm Electronics – Circuits for the Hobbyist
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