Forums

Which oscillator?

Started by Unknown October 17, 2014
<meow2222@care2.com> wrote in message 
news:e26709e0-9ecc-4465-a217-a125a0f9fff9@googlegroups.com...
> On Saturday, October 18, 2014 9:44:24 PM UTC+1, meow...@care2.com wrote: >> On Saturday, October 18, 2014 12:10:47 AM 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. (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 > >> OK, I got spicy.... > >> But its suffering problems, and I'm not seeing why. > > Have played with a multivibrator, and as someone suggested its pretty much > bulletproof. Just the job! Thankyou everyone. > > > NT
Try a darlington for Q1 or add another 2N2222 so the emitter of the second drives the base of the first. It will drive 50 ohms but it's a little distorted and clipped at the bottom. You could lower R4 to 25 ohms and get a cleaner sine wave, but the circuit would draw 140 mA. --- news://freenews.netfront.net/ - complaints: news@netfront.net ---
On Monday, October 20, 2014 4:00:56 AM UTC+1, Bill Bowden wrote:
> <meow2222@care2.com> wrote in message > news:e26709e0-9ecc-4465-a217-a125a0f9fff9@googlegroups.com... > > On Saturday, October 18, 2014 9:44:24 PM UTC+1, meow...@care2.com wrote: > >> On Saturday, October 18, 2014 12:10:47 AM 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. (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
> >> OK, I got spicy.... > > > >> But its suffering problems, and I'm not seeing why.
> > Have played with a multivibrator, and as someone suggested its pretty much > > bulletproof. Just the job! Thankyou everyone.
> Try a darlington for Q1 or add another 2N2222 so the emitter of the second > drives the base of the first.
I wondered about that, or adding an output stage so loading doesnt affect the osc. But once there are 2 trs, the multivibrator makes more sense.
> It will drive 50 ohms but it's a little > distorted and clipped at the bottom. You could lower R4 to 25 ohms and get a > cleaner sine wave, but the circuit would draw 140 mA.
Yes, but not compatible with running it off flat batteries found thrown out. Also would consume batteries much quicker. Everything's a tradeoff. NT