Thursday, March 14, 2013

100 LED’s Solid State Oscilloscope circuit

It
uses a matrix of 100 LED’s for a display, and does suffer from being
slow and having rather poor resolution. Still we could display a sine
wave running at 500Hz without trouble, that that's not all that
dissimilar to commercial solid state oscilloscopes.
The
circuit displays an understanding of the mechanics of displaying an
analogue waveform. The timebase is simply a LM555 generating a
horizontal sweep, while the vertical amplifier is LM3914 with a trimmer
pot on the front. It's extremely simple, but it works.
The
LED’s are multiplexed by a 4017 driven by the timebase. This
arrangement reduces the current requirements considerably, no mean
consideration when operating from the power supply of the device under
test.
With
a device like this, making the unit as small as possible is obviously a
consideration. Katz decided to make his own box out of perspex so that
he could make it just as big as the circuit board, and no bigger. He was
also able to give the thing a fancy shape rather like a bought one.
On
the basis that this project had the highest combination of imagination,
design ingenuity, construction and documentation, we made it the
national winner.
You can see the circuit for this project on page 108 of The Forrest Mims Engineer's Notebook.
It's published by LLH Technology Publishing (formerly High Text
Publications) and is under $20.00. The ISBN number is 1-878707-03-5.
This a 8.5"x11" soft cover manual. This book is full of circuits that
the electronics hobbyist will want to try, using many common components.
The circuit for this scope was published in August of 1979 in
Popular Electronics magazine too, with more details than the book goes into.
The part list:
PC Board (shown is RS 276-147, 4.5"x6.25")
14 pin dip IC socket
16 pin dip IC socket
20 pin dip IC socket (for the 18 pin LM3914)
100 Red LEDs
LM3914 Dot/Bar Display Driver
4011 Quad Nand Gate
4017 Decade Counter/Divider
100K trimmer pot
1K trimmer pot
SPDT switch
1K resistor
0.1μf capacitor
9V battery
9V battery snap
small amount of wire, bus wire,

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