Do-it-yourself electronics, particularly digital clocks, have been in the news this week.
And there are a lot of things to talk about with this story, and from Tumblr to the White
House, people are talking about them.
But we here at SciShow were interested in how digital clocks actually work.
Well first, you need a power source.
That’s either a battery, or a wire running into the wall.
Most consumer digital clocks use an ordinary plug, with a transformer that steps down the
power supply before the current runs into the clock.
Plus, there can be a connection for a nine-volt battery, as a backup power source.
Next, a clock needs a heartbeat -- some way of counting regular intervals in order to
keep time.
In a traditional pendulum clock, the heartbeat comes from the swinging of the pendulum.
But in a digital clock, this heartbeat can be generated electronically, in a couple of
different ways.
It might use a crystal oscillator, for example -- a piece of quartz that vibrates at a regular
frequency when it’s attached to an electrical current.
Or, it might use a circuit that counts the oscillations of the electricity coming through
the wire.
These oscillations are measured in cycles per second, using units called Hertz.
So if your clock runs at 60 hertz, the electricity being fed to it is oscillating 60 times per
second.
Those oscillations are just the regular, built-in fluctuations in the amount of electricity
being fed into the electronics.
A digital clock counts those oscillations to keep time.
The third thing you need in a clock is a way to split up that heartbeat into different
units of time.
In a mechanical clock, that’s done with gears: A different set of gears connects the
pendulum to the hour hand, the minute hand, and the second hand, so they each move a different,
specific amount as it swings.
Digital clocks don’t have gears, of course.
Instead, they have a chip that counts the heartbeats, then acts like a simple calculator
to divide the number of heartbeats into conventional units of time.
So, if you have a signal that pulses 60 times every second, the chip counts the oscillations,
and for every sixty, it records it as one second having passed.
For every 3,600 oscillations, it records a minute; for every 216,000 -- that’s an hour.
Now the last thing you need for your clock is a display, like an LED screen, with a separate
circuit that lets it communicate with the counters.
That circuit is running its own simple program that tells the screen what to display based
on how much time has passed.
When the second counter reaches 10, for example, the program says to put a “one” and a
“zero” in these specific spaces.
And after the counter reaches 59, it cycles back to zero.
And that’s all you need!
A power source, a heartbeat, a counter that can divide up the heartbeat into longer measurements
of time, and a display screen, with its own circuit that tells it what to do with the
numbers generated by the counter.
In the world of modern technology, surprisingly simple.
Thanks for taking the time to watch this video, and thanks especially to this month’s President
of Space, S.R.
Foxley.
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