>> Jason White wrote:
>> Hello All. I'm currently working on a project that requires me to use
>> 2 1:16 multiplexers to interface with various peripherals due to
>> limited I/O. I'm curious how much (RC?) filtering would be required to
>> make a short fast pulse (eg. 1-10khz 1-5% duty cycle) a suitable
>> signal to drive a relay.
>> Thanks
>>
>> relay: odd Chinese 20A H-Bridge relay on hooked up via opto-coupler, No
>> other specs multiplexers: CD74HC4067M MCU - 16f690
>
> Just a suggestion, you might get a lower part count/space/cost solution i=
f
> you
> instead look at cascaded serial shift registers (74HC165, 74HC595 etc) fo=
r
> output
> expansion. Then you won't need R,C & possibly no FET either. I'm sure
> there are
> examples at piclist.com but I can't find any right now.

I agree. There are parts that Allegro used to make (6832 and similar) that
have a serial in, parallel out shift register plus a parallel latch plus
high current drivers. You shift the data out, latch it, and the output
fets are updated. TI makes similar 8 bit parts, but I can't find the part
number right now.

Harold


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