🚀 go-pugleaf

In article <2812@lll-lcc.UUCP> rzh@lll-lcc.UUCP (Roger Hanscom) writes:
> Anybody out there care to explain what is happening to my 5-volt
> (7805) regulated power supply on a TTL circuit, when I add one
> CMOS chip??  The TTL is basically a counter/display circuit, and
> I'm trying to feed it (cleaned up) 60 Hz (from AC) to count. A 4093
> does a pretty good job of cleaning up the rectified 60 Hz, but for
> convenience (lazy??) I supply the 4093 with the TTL +5 and ground.
> Any of the 60 Hz signal over 5+ (it's a little less than 10 volts!)
> gets into the +5 supply.  That's a pretty mean ripple, and it's no
> surprise that the TTL ceases to function under these conditions.

Put a 1 Meg resistor in series with the input to the 4093.  You
probably were allowing too much current to flow from the AC input
through the protection diodes in the 4093 to the +5 supply.

                                       +5
                                        _
                                        |
                                  in +------+  out
     10V AC ----------/\/\/\/--------| 4093 |o-------- to TTL
      60 Hz             1M0          +------+
                                        |
                                        V
                                       GND

-- 
Bruce Walker         ...uunet!utai!lsuc!isgtec!bmw         bmw@isgtec.uucp
"Remember Rule Number 79: When the tough get going, the weak get screwed."
ISG Technologies Inc.  3030 Orlando Dr. Mississauga.   Ont.  Can.  L4V 1S8