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Tempo displaySince we want a precise time reference, it's better to use a quartz-based oscillator. But, on the other hand, we need to be able to change the oscillator frequency. Shall we use two oscillators then ? One as a clock reference, and the other one as an adjustable frequency ? That's exactly what I did! Indeed, the CD4553 is a 3-Digit BCD Counter, and it has four very useful inputs:
- A clock input (CLK).
- A master reset input (RES).
- A latch enable input (LE).
- And a disable input (DIS).
Now that we have a reference clock at 32 Hz, we need to trigger the CD4553's inputs in the right order. The best thing to do is then to add a decimal counter between the CD4060 and the CD4553. Thanks to that, we will be able to trigger the different inputs sequentially.
So, what we want to do is:
- Disable the clock input of the CD4553 (DIS input)
- Set LE to zero, so we can memorise the new count, then set it back to one.
- Reset the counting (we are now ready to count).
- Set DIS to zero to finally count the pulses on the CLK input.
- Repeat from 1.
R1 = 1e3; R2 = 4.7e3; C = 100e-9; P = linspace(0, 10e3, 1000); Ra = R1; Rb = R2 + P; f = 1.44./(Ra + 2*Rb)/C; a = 100*(Ra + Rb)./(Ra + 2*Rb); figure(1) plot(P/1e3, f/6.4)...Read more »