Electronics -- 10xHz Precision Clock Generator
The main feqtures of this device were already described on the parent page.
The device presented here can generate a complementary clock signal
at frequencies of 10Hz to 10MHz in steps of factor 10. Thus, I
chose to call it "10xHz clock generator"
(with x being a number between 1 and 7). It can also be used
to manually create clock impulses using a press button.
NOTE: Due to the quick design requirement, there are some things which could be improved (especially PCB layout not presented here...)
The frequency is selected using two press buttons/swiches: S1 to switch
the frequency up by a factor of 10 and S2 to switch it down. The
frequency selection is determined by the three pins A,B,C at the 4051
which are just the binary representation of the x-value.
7 (i.e. A,B,C being HIGH) selects the direct signal from the
crystal-controlled oscillator OG1 while lower numers/combinations
select lower frqeuencies from the divide-cascade built-up with three
The output stage is done with two parallel 74AC04 inverters which
can source and sink up to 24mA each with slew rates at least as good as
the HC family. Due to the fact that the complementary signals travel
through a different number of inverters, they are not exactly in sync but
the delay of about <7ns should not make big trouble.
The CD4511 drives the LED display of the x-value (i.e. frequency). You may want to use 100 instead of 220 Ohm for R8.
Note: The design above leaves away all the bypassing capacitors. That is because I chose to solder them directly on the IC socket pins for optimum performance and because otherwise the required signal lines proved to make PCB design much more complicated in the past.