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Which oscillator?

Started by Unknown October 17, 2014
Hi folks. I'm looking to choose a couple of oscillators for 3rd world construction/use, and I'm very rusty on the properties of the numerous options. What's essential:
- reasonably frequency stable with quite widely varying psu voltage, eg 5-9v
- discrete parts only, ICs can't be counted on to be available
- common parts only, no tapped inductors etc
- the minimum of parts is a major choice factor

Plusses would be:
no inductors
npn trs only

The prime app is as a sig-gen. Frequncy range etc are determined more by BOM than anything else, its down to what can we manage with a few cheap parts. (I've used opamps for basic miniature pocket use sig gens, but can't do that here.)

A 2nd app for an LED strobe might also be handy. This would need a mark/space of 10:1 or so to get decent clarity of speed measurements. Again its a question of what can we do at minimum cost.


thank you, NT
On Fri, 17 Oct 2014 16:10:47 -0700, meow2222 wrote:

> Hi folks. I'm looking to choose a couple of oscillators for 3rd world > construction/use, and I'm very rusty on the properties of the numerous > options. What's essential: > - reasonably frequency stable with quite widely varying psu voltage, eg > 5-9v - discrete parts only, ICs can't be counted on to be available - > common parts only, no tapped inductors etc - the minimum of parts is a > major choice factor > > Plusses would be: > no inductors npn trs only > > The prime app is as a sig-gen. Frequncy range etc are determined more by > BOM than anything else, its down to what can we manage with a few cheap > parts. (I've used opamps for basic miniature pocket use sig gens, but > can't do that here.) > > A 2nd app for an LED strobe might also be handy. This would need a > mark/space of 10:1 or so to get decent clarity of speed measurements. > Again its a question of what can we do at minimum cost. > > > thank you, NT
It's cool that you're working on this. I'd suggest that if you're going to be doing much of this, that you start collecting electronics and amateur radio magazines from the 1960's and '70's. There should be a rich supply there. You can make a reasonably stable 6V-ish zener from a reverse-biased BE junction on a 2N2222-ish transistor. Then use that as a reference for a regulated supply. Do you just need a wiggly line on a scope, do you need square waves, triangle waves, sine waves, what? -- www.wescottdesign.com
On Friday, October 17, 2014 4:10:47 PM UTC-7, meow...@care2.com wrote:
> Hi folks. I'm looking to choose a couple of oscillators for 3rd world construction/use, and I'm very rusty on the properties of the numerous options. What's essential: > > - reasonably frequency stable with quite widely varying psu voltage, eg 5-9v > - discrete parts only, ICs can't be counted on to be available > - common parts only, no tapped inductors etc > - the minimum of parts is a major choice factor
Why not just whistle into a speaker or earbud? Or fit a tuning fork with a magnet and a coil of wire?
On Saturday, 18 October 2014 00:10:47 UTC+1, meow...@care2.com  wrote:
> Hi folks. I'm looking to choose a couple of oscillators for 3rd world construction/use, and I'm very rusty on the properties of the numerous options. What's essential: > - reasonably frequency stable with quite widely varying psu voltage, eg 5-9v > - discrete parts only, ICs can't be counted on to be available > - common parts only, no tapped inductors etc > - the minimum of parts is a major choice factor > Plusses would be: > no inductors > npn trs only > The prime app is as a sig-gen. Frequncy range etc are determined > more by BOM than anything else, its down to what can we manage > with a few cheap parts.
A two transistor multivibrator might be a good choice if you don't need to go to very high frequencies and you don't need a sine wave output. For audio and low rf, almost any npn transistors will work. From what I remember of building these with salvaged transistors a very long time ago they are very forgiving circuits. The output is a square wave or pulse train depending on component values. The frequency does vary a bit with supply voltage. However, the circuit "just works" with almost any components and has no inductors or anything else special. Frequency can be tuned by varying one of the resistors giving a variable repetition rate pulse train. John
On a sunny day (Fri, 17 Oct 2014 16:10:47 -0700 (PDT)) it happened
meow2222@care2.com wrote in
<4d0d5433-ef35-486a-9176-4123b679d440@googlegroups.com>:

>Hi folks. I'm looking to choose a couple of oscillators for 3rd world construction/use, and I'm very rusty on the properties of >the numerous options. What's essential: >- reasonably frequency stable with quite widely varying psu voltage, eg 5-9v >- discrete parts only, ICs can't be counted on to be available >- common parts only, no tapped inductors etc >- the minimum of parts is a major choice factor > >Plusses would be: >no inductors >npn trs only
mm that last thing... I got a lot of UJTs from ebay a while back. Simpler is hard. I showed a LED strobe with one here a while back.
>The prime app is as a sig-gen. Frequncy range etc are determined more by BOM than anything else, its down to what can we manage >with a few cheap parts. (I've used opamps for basic miniature pocket use sig gens, but can't do that here.) > >A 2nd app for an LED strobe might also be handy. This would need a mark/space of 10:1 or so to get decent clarity of speed >measurements. Again its a question of what can we do at minimum cost. > > >thank you, NT >
On Saturday, October 18, 2014 2:30:27 AM UTC+1, Tim Wescott wrote:
> On Fri, 17 Oct 2014 16:10:47 -0700, meow2222 wrote:
> > Hi folks. I'm looking to choose a couple of oscillators for 3rd world > > construction/use, and I'm very rusty on the properties of the numerous > > options. What's essential: > > - reasonably frequency stable with quite widely varying psu voltage, eg > > 5-9v - discrete parts only, ICs can't be counted on to be available - > > common parts only, no tapped inductors etc - the minimum of parts is a > > major choice factor > > > Plusses would be: > > no inductors npn trs only > > > The prime app is as a sig-gen. Frequncy range etc are determined more=
by
> > BOM than anything else, its down to what can we manage with a few cheap > > parts. (I've used opamps for basic miniature pocket use sig gens, but > > can't do that here.) > > > A 2nd app for an LED strobe might also be handy. This would need a > > mark/space of 10:1 or so to get decent clarity of speed measurements. > > Again its a question of what can we do at minimum cost. > > > > thank you, NT
> It's cool that you're working on this. > I'd suggest that if you're going to be doing much of this, that you start=
=20
> collecting electronics and amateur radio magazines from the 1960's and=20 > '70's. There should be a rich supply there.
Interesting.
> You can make a reasonably stable 6V-ish zener from a reverse-biased BE=20 > junction on a 2N2222-ish transistor. Then use that as a reference for a=
=20
> regulated supply.
Does that trick work with almost any npn tr? Its impractical to specify spe= cific trs, but no problem to say 'this size npn.' Zeners should be availabl= e too, but its potluck what the voltages would be. It would be a real plus to be able to calibrate the frequency dial and/or s= witching, and have it stay on target regardless of how many cells it runs o= ff, or how flat they are.
> Do you just need a wiggly line on a scope, do you need square waves,=20 > triangle waves, sine waves, what?
Basically want a pocket tool thats useful to people learning and doing elec= tronics in its various forms. So I guess there's room for minimal and more = capable kit. I'm looking to start with something minimal as its quicker to = design & write up, and quicker & cheaper to build, thus can benefit more pe= ople. So for the first version, pretty much any wave would be of use. NT
On Saturday, October 18, 2014 8:56:17 AM UTC+1, jrwal...@gmail.com wrote:
> On Saturday, 18 October 2014 00:10:47 UTC+1, meow...@care2.com wrote:
> > Hi folks. I'm looking to choose a couple of oscillators for 3rd world c=
onstruction/use, and I'm very rusty on the properties of the numerous optio= ns. What's essential:
> > - reasonably frequency stable with quite widely varying psu voltage, eg=
5-9v
> > - discrete parts only, ICs can't be counted on to be available > > - common parts only, no tapped inductors etc > > - the minimum of parts is a major choice factor > > Plusses would be: > > no inductors > > npn trs only > > The prime app is as a sig-gen. Frequncy range etc are determined > > more by BOM than anything else, its down to what can we manage > > with a few cheap parts.
> A two transistor multivibrator might be a good choice if you don't > need to go to very high frequencies and you don't need a sine wave > output. For audio and low rf, almost any npn transistors will work. > From what I remember of building these with salvaged transistors > a very long time ago they are very forgiving circuits. The output > is a square wave or pulse train depending on component values. > The frequency does vary a bit with supply voltage. However, the > circuit "just works" with almost any components and has no inductors > or anything else special. Frequency can be tuned by varying one of > the resistors giving a variable repetition rate pulse train. > John
That's 1 of the 2 possibles I've looked at. The main downside is the need t= o change at least 2 component values to vary frequency, and practically 4. = A ganged VR could change frequency over 10:1, but to shift decade would mea= n switching 2 caps. And there is the varying with Vcc, but realistically I = think that's going to happen with any basic 1 or 2 tr oscillator. The other one I looked at is 1 tr with RCRC feedback. Again multiple value = changes needed to change frequency, and the load would affect freq too. But= its certainly basic, with just 1 tr. But the switching isn't. NT
On Saturday, October 18, 2014 9:34:30 AM UTC+1, Jan Panteltje wrote:
> On a sunny day (Fri, 17 Oct 2014 16:10:47 -0700 (PDT)) it happened > meow2222@care2.com wrote in > <4d0d5433-ef35-486a-9176-4123b679d440@googlegroups.com>:
> >Hi folks. I'm looking to choose a couple of oscillators for 3rd world construction/use, and I'm very rusty on the properties of > >the numerous options. What's essential: > >- reasonably frequency stable with quite widely varying psu voltage, eg 5-9v > >- discrete parts only, ICs can't be counted on to be available > >- common parts only, no tapped inductors etc > >- the minimum of parts is a major choice factor > > > >Plusses would be: > >no inductors > >npn trs only
> mm that last thing... > I got a lot of UJTs from ebay a while back. > Simpler is hard. > I showed a LED strobe with one here a while back.
The need for a UJT would much reduce the ability to build the things. A UJT LED strobe does sound interestingly minimal, but I'm not convinced its practical due to the shortage of UJTs in scrap appliances. NT
On a sunny day (Sat, 18 Oct 2014 06:51:56 -0700 (PDT)) it happened
meow2222@care2.com wrote in
<2cfe163d-d52d-4766-9e27-b044a0a09435@googlegroups.com>:

>On Saturday, October 18, 2014 9:34:30 AM UTC+1, Jan Panteltje wrote: >> On a sunny day (Fri, 17 Oct 2014 16:10:47 -0700 (PDT)) it happened >> meow2222@care2.com wrote in >> <4d0d5433-ef35-486a-9176-4123b679d440@googlegroups.com>: > >> >Hi folks. I'm looking to choose a couple of oscillators for 3rd world construction/use, and I'm very rusty on the properties >> >of >> >the numerous options. What's essential: >> >- reasonably frequency stable with quite widely varying psu voltage, eg 5-9v >> >- discrete parts only, ICs can't be counted on to be available >> >- common parts only, no tapped inductors etc >> >- the minimum of parts is a major choice factor >> > >> >Plusses would be: >> >no inductors >> >npn trs only > >> mm that last thing... >> I got a lot of UJTs from ebay a while back. >> Simpler is hard. >> I showed a LED strobe with one here a while back. > >The need for a UJT would much reduce the ability to build the things. A UJT LED strobe does sound interestingly minimal, but I'm >not convinced its practical due to the shortage of UJTs in scrap appliances. > > >NT
Its probably cheaper to buy 100 UJTs on ebay than to get all that scrap, look for usable NPNs, get those out.. etc. I've build things from scrap PCBs, these days maybe the resitors are marked, but the capacitiors wont be, its all SMD, the transistors wont be marked either. Now you need a C and ohm meter too. Depends a bit how old the scrap is. With modern SMD parts you can do cheaper with new, all you need is a soldering iron and a pair of pliers. Its not like an SMD resistor or capacitor is expensive. Then better buy for 10$ parts, and they can make a hundred of these things and get hands on feeling with SMD. Veroboard.
On Sat, 18 Oct 2014 06:10:29 -0700, meow2222 wrote:

> On Saturday, October 18, 2014 2:30:27 AM UTC+1, Tim Wescott wrote: >> On Fri, 17 Oct 2014 16:10:47 -0700, meow2222 wrote: > >> > Hi folks. I'm looking to choose a couple of oscillators for 3rd world >> > construction/use, and I'm very rusty on the properties of the >> > numerous options. What's essential: >> > - reasonably frequency stable with quite widely varying psu voltage, >> > eg 5-9v - discrete parts only, ICs can't be counted on to be >> > available - common parts only, no tapped inductors etc - the minimum >> > of parts is a major choice factor >> > > Plusses would be: >> > no inductors npn trs only >> > > The prime app is as a sig-gen. Frequncy range etc are determined >> > > more by >> > BOM than anything else, its down to what can we manage with a few >> > cheap parts. (I've used opamps for basic miniature pocket use sig >> > gens, but can't do that here.) >> > > A 2nd app for an LED strobe might also be handy. This would need a >> > mark/space of 10:1 or so to get decent clarity of speed measurements. >> > Again its a question of what can we do at minimum cost. >> > > > thank you, NT > >> It's cool that you're working on this. >> I'd suggest that if you're going to be doing much of this, that you >> start collecting electronics and amateur radio magazines from the >> 1960's and '70's. There should be a rich supply there. > > Interesting. > >> You can make a reasonably stable 6V-ish zener from a reverse-biased BE >> junction on a 2N2222-ish transistor. Then use that as a reference for >> a regulated supply. > > Does that trick work with almost any npn tr? Its impractical to specify > specific trs, but no problem to say 'this size npn.' Zeners should be > available too, but its potluck what the voltages would be.
It works with all the small-signal ones that I've tried. I think it's a direct consequence of the doping profiles you need to get good transistor action -- but I don't know. I learned it from some ham radio electronics book or another.
> It would be a real plus to be able to calibrate the frequency dial > and/or switching, and have it stay on target regardless of how many > cells it runs off, or how flat they are. > >> Do you just need a wiggly line on a scope, do you need square waves, >> triangle waves, sine waves, what? > > Basically want a pocket tool thats useful to people learning and doing > electronics in its various forms. So I guess there's room for minimal > and more capable kit. I'm looking to start with something minimal as its > quicker to design & write up, and quicker & cheaper to build, thus can > benefit more people. So for the first version, pretty much any wave > would be of use.
I think that to start you want some sort of multivibrator, and you want to pull in your horns on stability and accuracy. -- www.wescottdesign.com