The "Octopus" component checker.

[The March Muppet]

I'm certain most of you will remember the filament trafo/oscilloscope component checker of better times?

I've been putting an idea pen to paper for fun to build a slightly different integrated version using four 5 x 7 LED matrices (10 vertical x 10 horizontal - the leading and trailing two columns left no connection), the "Deflection" done via a pair of LM3914s (transistors to invert the horizontal). The original block diagram idea intended to use a textbook Wien bridge op-amp sine wave genny, but the actual schematic as IO generate it has left me a bit confused.

The displays and 3914's make an acceptable rough X/Y "'scope", and I have a single output sine wave generator referenced to 0V - but .. I'm not certain how to connect the two and incorporate component probes. As well, seems to me that I need to generate a cosine for horizontal deflection, no?

 

[The March Muppet]

This is what I'm thinking.

A little battery powered novelty - but functional - circuit that'll fit on an open can of tuna.

 

[dr pepper]

With 1 x Lm3914.
Your 10 rows all commoned to the Lm3914, the cathodes for the coumns then go to a 1 of 16 decoder wired as a 1 of 10, the decoder scans the columns, the decoder being controlled by a binary counter / oscillator, the o/p of the binary counter as well as going to the 1 of 16 also goes to an R - 2R ladder / low pass filter, this generates your X sine wave, a pure sineave isnt that important.
Then this goes through an op amp etc to the device under test, the return going to the imput of the Lm3914, the display sacns horizontally and simulatneously genertaes the sinewave, which is then displayed via the Dut.
Not bad for a quick think on xmas day while in my new massage chair.

Of course a much quicker better way would be to program an arduino or something.

 

[The March Muppet]

I'll have to draw that out to get a better intuitive handle on the concept. Should have a '154 in the bin, but again - I want this circuit to fit on a bit of perfboard cut to fit on top of a can of fish.

Arduino - PIC? No. Not the way that I "want" to do it. I don't really enjoy IDE's and C to make something and the idea of the build is "enginartistry" rather than simply a solution - akin to it's more elegant to use a 20W audio amp module rather than a used compactron to build a 4W amp - but the latter has a certain cool factor, as well - my "shop" now the unheated rear of a 35 year old van full of ancient silicon. I'm a 6 hour round trip to the nearest electronics shop, and the postal service doesn't deliver here. I use what I have.

 

[dr pepper]

I had nothing electronics supply wise, then a major component supplier opened round the corner, still not majorly useful as they want to sell me bags of things.
I have drawers full of pulled parts however.

 

[The March Muppet]

Aye, the "propane parts pull" - I know it well. . These days I keep absolutely everything.

The state of the store front suppliers are dismal these days - last time I was in Mississauga they didn't have (relative) jellybean bits like the 567, 2907 and the like. I could technically Digi, but I'd have to take a day off work to pick up a package at the Godfrey P.O.

Love the MAR avatar btw.

 

[dr pepper]

I use a hot air gun and a weld bay to pull parts, same idea.
Most of the retail electronic component places as far as I can tell here in the Uk have gone, just component houses now & ebayers.
My mrs thinks its a chick feeder, I recently read a book about someone keeping evil demons in one!

 

[The March Muppet]

Ugh .. already having the 3914's and 2SA733's (GP PNP) on the board - and reckoning that full CMOS would allow for an unregulated battery supply that should work 5-10V I finished the mock up today.

Total rubbish.

The quadrature oscillator output was so ugly that the displayed waveform was unrecognizable and useless. Of course I did pop in a pair of 1973 dated 741's.

Considering running a dual supply with a 7660 instead of the op amps single ended and swapping out the fixed resistors for trim pots and trying to tweak the butt ugliness into something a bit more sinusoidal, but probably just wanking. I may need an entirely different OSC topology.