ELM411
Example Application
Figure 1 shows the ELM411 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.
The toggle input (In3) allows the user to select
motor direction using a momentary switch, as shown.
Due to the latch action,
a selected direction is
maintained for subsequent step inputs, without any user
intervention. The second debounce circuit has been
used in this case to simply invert the level of Out3,
providing a logic high level to the ELM310 at powerup.
This has been done to ensure that the startup direction
will be clockwise.
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 ELM411.
For more permanent installations, consideration
should be given to protecting the ELM411 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,
so there will be no problems with the logic levels.
A
+5V
1
2
3
4
8
7
6
5
To winding
drive circuits
0.1µF
B
C
D
Direction
5
6
7
8
4
3
2
1
+5V
Step
Figure 1. Manual Control of a Stepper Motor
ELM411DSB
Elm Electronics – Circuits for the Hobbyist
4 of 4
< http://www.elmelectronics.com/ >
ELM [ ELM ELECTRONICS ]
