How to make a Voltage Controlled Oscillator

Rich Grise:

The retarding version? :D

I just noticed that you referred to the fifth, not the sixth processor designed by Federico Faggin. Oops, for a second I forgot that Bell invented the telephone.

Are you sure that was 8008 not 8080 ?

VLV

.

Bearing in mind that you think the 555 is the "right device" for any number of jobs.

e

More modern - if not by much. The real distinction is that there are almost always better ways of doing a job than with a 555, while the

4046 (and its derivatives) are still good solutions for many jobs that involve a phase-locked loop. It always was a more specialised part than the 555, but fulfilled it's particular function remarkably well.

He's putting his own circuit together to do a job that he wants done. That's design and development.

True enough. But the competence that I developed with PDP-8 assembler in 1968 doesn't translate directly into programming the lastest =B5C from Arizona Microchip. It did make it easy to get a 6800 to do what I wanted it to do some fifteen years later, but then I was taking advantage of somebody else's development system and modifying his code rather than putting something togehter from scratch.

-- Bill Sloman, Nijmegen

Jim should remember that I not only knew about it but got it to work in a system I put togehter back in 1972. I didn't think much of the MC4024 or the MC4044 by the time I'd managed to get them to do what I wanted - the bipolar process that Jim was stuck with didn't do him any favours - but I certainly know about those chips, and have mentioned this here from time to time.

-- Bill Sloman, Nijmegen

Vladimir Vassilevsky:

He said "seventies" and "2001 just released".

But he also did not mention "not readily available".

Well, it was in an 18-pin DIP, and had "8008" printed on it.

Thanks, Rich

(news)=id&id(news)=2 (museum)=id&id(museum)=22

Hope This Helps! Rich

Could it be 8880 ?

VLV

--
Being far more familiar with, and far less arbitrarily biased against
the 555 than you are, I'm in a much better position to judge its
'rightness' for any number of jobs.

[snip]

Slowman can't even do a hand analysis of how a 555 works internally. If he got some "tools" he'd blow his head off :-) ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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               I can see November from my house :-)

"The Journey is the reward"

eff.com

I was going to suggest this type of circuit, but it seemed to complicated. One 'gotcha' to look out for is the supply reference that Spehro mentioned. Variation in the supply voltage causes a variation in the frequency. (I was biten by that.)

George H.

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But since you don't seem to be as familiar with anything more modern, you judge it to be the "right" choice in a lot of cases where less biassed designers would come up with something different, better, and sometimes even cheaper.

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l

That was your interpretation. The 4046 is distinctly more modern in the sense that it was designed to handle a specific job, where the 555 is a timing element tied to a switching transistor - a jack of all trades and a master of none.

You do have your obvious prejudices.

the 555,

Exactly right - though the 555 is more like the Chinese version of the Swiss army knife, made with soft steel that barely cuts butter.

o h

He'd like to be doing assembly and test, which is why he asked us for a design. Sadly, the designs we can give are never going to exactly adapted to solve his particular problem, so he is stuck with at least a measure of design and development.

To solve the problem as Jim understands it. Nobody who posts a problem here gives enough background detail to let anybody design a solution that is going to be perfectly adapted to solving the problem that OP actually needs solved. As you should know, most customers don't appreciate the exact nature of the problem they are facing, and what they want is rarely exaclty what they actually need.

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Not a problem. I've contemplated doing it a couple of times, but the motivating circumstances changed before I'd got around to spending the money. I've now got a Farnell account - that I've never actually used

- from one of those episodes.

But there is a price attached to buying the tools and investing the effort to get them to do what you want.

-- Bill Sloman, Nijmegen

Why should I bother? I've got Hans Camenzind's "Designing Analog Chips" which discusses the circuit in some detail. It isn't exactly a complicated circuit.

If the worst came to the worst I could shoe-horn it into LTSpice and play with it there.

-- Bill Sloman, Nijmegen

I'll donate a couple screwdrivers...

--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

Fer Cry's sakes, how many times do I have to tell you guys? It was a Scelbi 8H, with an intel 8008 - that's eight, zero, zero, eight. Mine only came with 256 bytes of RAM. And I didn't technically buy it. I had just plunked down about $600.00 for a Heathkit IO-10 or maybe IO-11; It was really cool looking; similar to a TEK 465, i.e., low aspect ratio (or high - about a foot wide by about 5" tall by about 17" deep)

And when I assembled it, it didn't work. But a coworker had the Scelbi which he didn't like having to toggle everything in, but it had cost him about 6 bills, so we traded straight up. He also gifted me with a model 13 teletyps. (60 mA current loop, 60 WPM.)

8008 machine code is almost microcode, but it did have an 8-level stack. ;-)

Cheers! Rich

No need. I've got a bunch already that cover almost all of the screw heads that come into the house - slotted, Philips, Pozidrive and the weird three-lobed thing that drives the self-tapping screws that hold the leaf-blower together.

In any event the "tools" that Jim was talking about were software - things like PSpice and Hi-Lo, to confine the discussion to the ones that you might have heard about.

-- Bill Sloman, Nijmegen

F. Bertolazzi:

I found the prototype!

The NE555 was the metronome, adjustable with the blue trimmer. One of the buttons was for changing tune, the other... who knows.

Lazy kid (well, the program was written in hex codes painfully typed on a friend's eprom programmer), I used a brand new 8253 (look at the date stamp!) to make the notes, three at a time!!! The resistors near the 2n1711 were the mixer. The greasy label on the Z-80 had the pin names written on it.

Rich Grise:

That reminds me the hours it took to load (and reload and again) the boot memory of the Varian microcomputer used as collision avoidance system.

Rich Grise:

Hey, not me! I was even convinced that the 8008 was released before 1970 (as 2001 was).