a bit challenging for me
posted by Physics_freak on .
i got a planning and design lab to do
this is the scenario
You are give an OR gate which registers 1, when the voltage is +5 volts or greater. Use this gate to determine the frequency of a voltage supply of peak voltage +5V.
i don't know what to do..is it that we vary the frequency of the power supply to get several readings (up until the point where the OR gate doesn't register at 1) and then plot a graph, find an equation to get the frequency ??? confused and would really appreciate the help

Are you allowed to also use a known power supply and combine signals?

i suppose..since its a lab that i'm suppose to design, anything is at my dispose

Well, I am thinking that if you maybe add the known frequency output to your unknown output, you will get a beat frequency that goes to steady AC as your difference goes to zero.
sin (w t)+ sin(w2t) = 2 sin .5(w+w2)t cos .5(w  w2)t
when your unknown w = 2 pi f = your known w2 = 2 pi f2, you will no longer have your beat frequency and if for example both signals are 5 volts peak, you will get steady AC at 10 volts peak. When w is less or more than w2, your signal will go up and down at low frequency ww2 
PS
That is how pianos are tuned. When the frequency is the same as that of the pitch fork, the tuner hears a steady tone, Not up down up down :) 
i kind of understand but its a bit confusing

where did u derive ur w w2 eqn frm?

Trig tables
sin a + sin b = 2 ...... 
OO ..okay...this is a bit hard when you don't do math as a subject at higher levels

well thanks...i'll try to figure out how to make a lab out of the info.
THNX MUCH! 
You are welcome. I hope it works. Beat frequencies work for piano tuners anyway :) Good luck !!!