In article <4d3v6f$5fa@henge2.henge.com> words@henge.com (Michael O'Connor) writes:
>From: words@henge.com (Michael O'Connor)
>Subject: Radio button circuit
>Date: 11 Jan 1996 21:24:31 GMT
>I am looking for a digital circuit that emulates the selector buttons
>on a radio. A pulse at one of 1 through n inputs will latch the
>corresponding output until another input is pulsed.
Rather easy:
o +Vdd
|
|
o Data-latch
|<= switch ---
o | |
|-----------------------------|D O|--o out
| | | | E |
| | --- |100nF ---
100| | --- | |
K | | | 1N4148 100nF |
___ ___ -|>|----------||--------|
/// /// | | | | |
| | | | | - |
from other -|>|-- | | | | ^ --> to E other
switch 1N4148 | | | latches
___ ___ ___
/// /// ///
10K 100K 1N4148
How it works:
when pushing the switch, a High level is applied to the D-input of the
associated data-latch. Any switch pushed will also cause a High-level pulse on
the E input of all latches (the diodes function as a wired-or circuit).
This way all data-latches will transfer their input level to their output; if
only one switch is pushed, only one input will be high (and therefore the
output will go high too), the others will stay low. The rightmost 1N4148 diode
prevents the E-input from receiving a voltage below 0V, when the switch is
released.
So what you need per switch is a 100K resistor, a 100nF capacitor (to debounce
the switch contacts), a 1N4148 diode and one data-latch unit.
The pulse-generating circuit (10K/100nF/100K/1N4148) is only needed once.
When you use the CMOS 40373 or the 74HC373 you get 8 latches per device.
Success,
Richard
Richard Rasker
Calslaan 54-11
7522 MG Enschede
Holland
tel. +31-(0)53-4350834
Date: Sun, 14 Jan 1996 19:05:09 UNDEFINED
Original Subject: Re: Radio button circuit