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[JAZZY]

hey fellow techies,
I'm designing a circuit that has a key pad, the pad has an assortment of momentary push switches and regular on/off stay switches. i'd like to have an led for every switch to indicate when the momentary switch has been pushed (meaning the switch is active).(just like the caps-lock key on your computer keyboard and it's led indicator)is there a simple ic that can do this job( what is the IC number?) how else can i achieve this?. The whole key pad is running on 5 volts linked to a 40pin microcontroller and there are about 40 keys on the key pad. Your help will be highly appreciated. thanks in advance .... jazz

[bodgy]

If you want momentary led'ing then just add some leds via limiting resistors to the keypad column lines. If the keypad has a built in diode matrix for key selection then you could (laboriously) substitute leds for them.<p>If you want to toggle thenI would either use the microcontroller to switch leds on (I assume you have the wherewithal to reprogram the uC)40 pins for a 40 pin keypad is a bit excessive unless you want a stand alone keyboard controller so a bit of multiplexing would leave some i/o free.<p>Alternatively perhaps using some form of x:16 encoder from the 74 series might do the job.<p>bodgy

[N8ZUX]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by JAZZY:
hey fellow techies,
I'm designing a circuit that has a key pad, the pad has an assortment of momentary push switches and regular on/off stay switches. i'd like to have an led for every switch to indicate when the momentary switch has been pushed (meaning the switch is active).(just like the caps-lock key on your computer keyboard and it's led indicator)is there a simple ic that can do this job( what is the IC number?) how else can i achieve this?. The whole key pad is running on 5 volts linked to a 40pin microcontroller and there are about 40 keys on the key pad. Your help will be highly appreciated. thanks in advance .... jazz<hr></blockquote><p>Are you seeking to use something similar to a radio keypad or a telephone ?? just curious,