ELM415 Ver la hoja de datos (PDF) - Elm Electronics
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ELM415 Datasheet PDF : 5 Pages
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ELM415
Example Applications (cont’d)
A variation of Figure 2 is shown in Figure 3. It uses
series resistors on the pushbutton inputs, and has also
had its autorepeat function modified slightly.
This circuit assumes that the pushbuttons are to
be mounted at a distance from the ELM415, which is
why the series resistors have been added. This is a
good practice to follow whenever working with CMOS
circuits that might be exposed to electrostatically
induced charges, as could be the case due to the extra
wiring for the switches. The resistors help to limit
induced currents which will flow through the IC’s
internal protection diodes during a discharge, and in
doing so reduce the chance of latchup problems.
Generally, we recommend that protection resistors be
installed close to the IC whenever wiring is to extend
from the circuit by more than about twelve inches.
The other difference between the circuits of
Figures 2 and 3 is the connection between pins 5 and
6. This can best be explained by considering that in
Figure 3, due to the internal pullup resistor on pin 6,
pin 5 will normally be at VDD (enabling the repeat
function). When the Down button is pressed, the
autorepeat function will remain enabled, and multiple
pulses will be output. When the Up button is pressed,
however, it will pull both pins 5 and 6 low, disabling the
autorepeat and allowing only a single pulse to be
generated. This is useful if one wants the user to
explicitly press a button for each advance in one
direction, but will allow a rapid transition to a ‘safe’
position when the other button is pressed. This may be
a desireable feature if controlling the temperature in a
heater circuit, for example.
5
1KΩ
6
1KΩ
7
Up
8
Down
4
3
2
VDD
1
VDD
1
8
2 AD5220 7
3
6
4
5
Figure 3. Controlling a digital potentiometer (with rapid down)
Our final example shows how easily one can use
the ELM415 as a ‘one-shot’ or monostable
multivibrator in a reset circuit. Often one has the need
to reset a circuit using a pushbutton, but multiple
5
Reset
6
7
8
4
Reset
3
Output
2
VDD
1
resets due to bouncing switches would be an
annoyance. Using the circuit of Figure 4, one can
generate a single clean reset pulse whenever the
pushbutton is pressed. If the circuit needs a negative-
going pulse, simply connect pin 4 to VDD rather than
VSS.
Hopefully this has provided you with several ideas
for using the ELM415 in your next project. Have you
considered using it to reset a timer whenever a contact
closes, or to count switch closures, or to determine an
object’s direction based on the order in which the two
switches operated…
Figure 4. Manual reset circuit
ELM415DSA
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