solid state oscilloscope, greater range - how to

neazoi · Mar 4, 2013

Hello I have found this solid state oscilloscope that does not use a micro and it is very easy to make. **broken link removed** (10mb)
The author states it goes up to 1MHz with the optional time base circuit.

I was wondering, can I make it work in higher frequencies, using an even faster timebase circuit and leave the rest of the circuit unchanged?

FvM · Mar 4, 2013

The author states it goes up to 1MHz with the optional time base circuit.

LM3914 isn't designed to work correctly above a few 10 or maximum 100 kHz. There even isn't a dynamic specification of the chip. Also ULN2803 column driver will show considerable on- and off-switching times.

neazoi · Mar 4, 2013

FvM said:
LM3914 isn't designed to work correctly above a few 10 or maximum 100 kHz. There even isn't a dynamic specification of the chip. Also ULN2803 column driver will show considerable on- and off-switching times.

any thoughts of making it go higher about 10-30mhz?

FvM · Mar 4, 2013

You'll need a fast ADC, 20 to 50 MS/s 8-Bit converters are rather cheap now. Instead of transfering the sampled data to a display in real time you can better store it, making a basic digital storage oscilloscope.

neazoi · Mar 4, 2013

FvM said:
You'll need a fast ADC, 20 to 50 MS/s 8-Bit converters are rather cheap now. Instead of transfering the sampled data to a display in real time you can better store it, making a basic digital storage oscilloscope.

How about "cheating" and using a mixer to downconvert to 20KHz?

thylacine1975 · Mar 5, 2013

Wow... that project article brought back some memories... and not necessarily good ones. Save yourself the pain and DON'T build it!

I built a remarkably similar unit back in the late 80's - a couple of cascaded decade counters drove the x-axis of the LED array, and an LM3914 drove the y axis. After spending an eternity building it on a wire-wrap board (and don't get me started on how much of my precious newspaper run money went into [then] hyper-expensive LEDs...) it was C.R.A.P. Granted, the main problem with the unit I constructed was the absence of a decent timebase triggering mechanism - something that this unit seems to have sorted out. That aside though, the display resolution was practically unusable. It was fine if you wanted to look at a textbook sine wave out of the high school signal generator, but utterly useless for any prototyping/debugging work.

Sure, it's a neat curiosity, but a PICxx driving a Nokia 5110 LCD (e.g. https://www.youtube.com/watch?v=xIoTnZGjgoM) can be had for a fraction of the price and smashes the LED oscilloscope in performance.

Please don't

neazoi · Mar 5, 2013

thylacine1975 said:
Wow... that project article brought back some memories... and not necessarily good ones. Save yourself the pain and DON'T build it!

I built a remarkably similar unit back in the late 80's - a couple of cascaded decade counters drove the x-axis of the LED array, and an LM3914 drove the y axis. After spending an eternity building it on a wire-wrap board (and don't get me started on how much of my precious newspaper run money went into [then] hyper-expensive LEDs...) it was C.R.A.P. Granted, the main problem with the unit I constructed was the absence of a decent timebase triggering mechanism - something that this unit seems to have sorted out. That aside though, the display resolution was practically unusable. It was fine if you wanted to look at a textbook sine wave out of the high school signal generator, but utterly useless for any prototyping/debugging work.

Sure, it's a neat curiosity, but a PICxx driving a Nokia 5110 LCD (e.g. https://www.youtube.com/watch?v=xIoTnZGjgoM) can be had for a fraction of the price and smashes the LED oscilloscope in performance.

Please don't

Yes I didn't expect something really usefull, I allready own a 100MHz surplus oscilloscope, which bought almost at the same cost as this little one will cost. It is just fun to build just 4 pcbs and have a quite portable oscilloscope made out of "discrete" chips. This project is so complete and because no micro, it can be build from a hobbyist almost two decades ago from it's publication

Nevertheless I would be glad if I could see a better micro/lcd oscilloscope that can do up to 30MHZ, but I haven't seen one neither. Most of them go up to a max of 5MHz.

Any propositions/schematics?

FvM · Mar 5, 2013

I once designed a similar LED matrix display for an analog audio spectrum analyzer, with 16x30 Leds, if I remember right and kHz scan clock. That's an appropriate application for a low resolution display and it's achievable speed. Needless to say, that the application can be implemented with a recent microcontroller.

neazoi · Mar 5, 2013

FvM said:
I once designed a similar LED matrix display for an analog audio spectrum analyzer, with 16x30 Leds, if I remember right and kHz scan clock. That's an appropriate application for a low resolution display and it's achievable speed. Needless to say, that the application can be implemented with a recent microcontroller.

I haven't seen anything at higher than 5MHz frequency...

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