"Heavy Duty" Square Wave Oscillator - Electronic Circuits Projects Diagrams Free

Hayato · 22nd June 2006, 03:26 AM

Hello,
I'm projecting an square wave oscillator that needs to function almost 24h/day under temperatures ranging from 80°C to 50°C.

I'm thinking of Astable Multivibrators, but which kind of those multivibrators are adequated for the job? The old and good TR type, does the job? Or an IC type would be more adequated?

Thanks.

Russlk · 22nd June 2006, 04:22 AM

Go with the IC, it will be simpler and better. Use an automotive rated one such as SA555, rated for -40C to +85C.

**Nigel Goodwin** · 22nd June 2006, 09:30 AM

Another concern is how accurate does it need to be?, any RC type oscillator (including a 555) isn't going to very stable over that temperature range.

Dr.EM · 22nd June 2006, 11:12 AM

Yeah, any RC oscillator won't be extremely accurate, but you can maximise stability by using metal film resistors and either polystyrene or silvered mica capacitors for the timing components. These parts are more stable.

**Nigel Goodwin** · 22nd June 2006, 12:25 PM

Quote:

Originally Posted by Dr.EM

Yeah, any RC oscillator won't be extremely accurate, but you can maximise stability by using metal film resistors and either polystyrene or silvered mica capacitors for the timing components. These parts are more stable.

Yes, or (much better) use a crystal to generate the required frequency, divided down as required - or an 8 pin PIC with an external crystal.

But it really depends what it's for?, what the require frequency is?, and if it needs to be stable and accurate?.

If it's not at all critical, a simple 555 would be fine - or even a standard astable multi-vibrator.

Hayato · 22nd June 2006, 05:50 PM

Thank you all.
Well, I'm avoiding the 555, because I need "constant" duty cycle.
If I add an potentiometer to vary the 555 oscillation frequency, its duty cycle will vary too.

The frequency ranges from 60Hz to 15kHz. It's not needed an extreme accuracy, minimum of about 90%. But it needs to be stable.

Are you sure xtal will be better? The vibration of car will not affect its physical structure?

I'll use to drive the ignition coil.

**Nigel Goodwin** · 22nd June 2006, 06:18 PM

Quote:

Originally Posted by Hayato

Thank you all.
Well, I'm avoiding the 555, because I need "constant" duty cycle.
If I add an potentiometer to vary the 555 oscillation frequency, its duty cycle will vary too.

The frequency ranges from 60Hz to 15kHz. It's not needed an extreme accuracy, minimum of about 90%. But it needs to be stable.

Are you sure xtal will be better? The vibration of car will not affect its physical structure?

I'll use to drive the ignition coil.

Well you've now completely altered your original question! - you never mentioned it had to be variable, obviously a crystal would make that difficult.

For a start I would suggest you try telling us EXACTLY what you are trying to do?.

Hayato · 22nd June 2006, 06:27 PM

Quote:

Originally Posted by Nigel Goodwin

Well you've now completely altered your original question! - you never mentioned it had to be variable, obviously a crystal would make that difficult.

For a start I would suggest you try telling us EXACTLY what you are trying to do?.

A-ha! Because of that I wanna build an astable oscillator!!

Well, as I've said before, I'll build a driver for ignition coils. I need a variable frequency one, because I wanna find the "optimal oscillation frequency" of the ignition coils.
In my mind, the optimal frequency is around 500 Hz ~ 1kHz, but I wish to find.

But I haven't changed my question, I still need that it be stable functioning almost 24h/day in temps ranging from 50°C to 80°C.

Thanks

philba · 22nd June 2006, 06:36 PM

To get the stability, the uC solution is going to be the best though how you adjust the frequency with stability is going to be tricky.

justDIY · 22nd June 2006, 06:49 PM

a pic with a hardware PWM should give you want you desire, just program in some buttons "UP/DOWN"

12F683 I believe has one hardware pwm and an onboard (iirc temperature compensated) rc clock

Hayato · 22nd June 2006, 07:13 PM

Philba,
After I find the "optimal frequency", I'll lock the frequency.

justDIY,
A phantom named uC is meeting me every time.

Just kidding.

But I need to do some PIC courses, my knowledge in that area is very low. And all material that I find about PIC programming in the internet is very weak.

Thanks

Hero999 · 22nd June 2006, 08:15 PM

90% accuracy?

Do you know that means?

It means is can vary by 90% and you've not said whether it's +/- 90% or both.

If a 1Hz oscillator has an accuracy of 90% that means it can drift between 1000 + 1000 * .9 and 1000 - 1000 * 9, that's a very big range! Are you sure you didn't mean 10%?

Hayato · 22nd June 2006, 11:34 PM

Quote:

Originally Posted by Hero999

90% accuracy?

Do you know that means?

It means is can vary by 90% and you've not said whether it's +/- 90% or both.

If a 1Hz oscillator has an accuracy of 90% that means it can drift between 1000 + 1000 * .9 and 1000 - 1000 * 9, that's a very big range! Are you sure you didn't mean 10%?

Ooops...
I forgot a decimal separator there, 9.0%

Sorry for that error.

panic mode · 23rd June 2006, 12:03 AM

so you want circuit that will stay stable within 9%, have adjustable frequency and duty cycle but not depend on each other?

there are several ways to do it, you can try mcu, use oscillator followed by monostable or use sawtooth oscillator followed by comparator with adjustable preset but there are also CMOS or TTL solutions...

Hayato · 23rd June 2006, 12:16 AM

Quote:

Originally Posted by panic mode

so you want circuit that will stay stable within 9%, have adjustable frequency and duty cycle but not depend on each other?

there are several ways to do it, you can try mcu, use oscillator followed by monostable or use sawtooth oscillator followed by comparator with adjustable preset but there are also CMOS or TTL solutions...

Yes, for example,
It keeps the duty cicle of 50% at 60 Hz.
It keeps the duty cicle of 50% at 500 Hz.
It keeps the duty cicle of 50% at 10000 Hz.

And so on. I was looking for a fixed duty cycle astable multivibrator mode of 555 and I've just found what do I want.

It's a 555 cofiguration that uses only a capacitor and a resistor to oscillate.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

22nd June 2006, 03:26 AM	#1
Hayato	"Heavy Duty" Square Wave Oscillator Hello, I'm projecting an square wave oscillator that needs to function almost 24h/day under temperatures ranging from 80°C to 50°C. I'm thinking of Astable Multivibrators, but which kind of those multivibrators are adequated for the job? The old and good TR type, does the job? Or an IC type would be more adequated? Thanks.

22nd June 2006, 04:22 AM	#2
Russlk	Go with the IC, it will be simpler and better. Use an automotive rated one such as SA555, rated for -40C to +85C. __________________ see my website: www.geocities.com/russlk

22nd June 2006, 09:30 AM	#3
Nigel Goodwin	Another concern is how accurate does it need to be?, any RC type oscillator (including a 555) isn't going to very stable over that temperature range. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

22nd June 2006, 11:12 AM	#4
Dr.EM	Yeah, any RC oscillator won't be extremely accurate, but you can maximise stability by using metal film resistors and either polystyrene or silvered mica capacitors for the timing components. These parts are more stable. __________________ Angry!? I'm absolutely electrolytic! Music web page: http://www.music-playground.net/artist/drem/

22nd June 2006, 05:50 PM	#6
Hayato	Thank you all. Well, I'm avoiding the 555, because I need "constant" duty cycle. If I add an potentiometer to vary the 555 oscillation frequency, its duty cycle will vary too. The frequency ranges from 60Hz to 15kHz. It's not needed an extreme accuracy, minimum of about 90%. But it needs to be stable. Are you sure xtal will be better? The vibration of car will not affect its physical structure? I'll use to drive the ignition coil.

22nd June 2006, 06:36 PM	#9
philba	To get the stability, the uC solution is going to be the best though how you adjust the frequency with stability is going to be tricky.

22nd June 2006, 06:49 PM	#10
justDIY	a pic with a hardware PWM should give you want you desire, just program in some buttons "UP/DOWN" 12F683 I believe has one hardware pwm and an onboard (iirc temperature compensated) rc clock __________________ If you don't have a planet, what good are gold bars? want to contact me directly? gmail gordonthree check out my project website: http://projects.dimension-x.net Favorite numbers: 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0

22nd June 2006, 07:13 PM	#11
Hayato	Philba, After I find the "optimal frequency", I'll lock the frequency. justDIY, A phantom named uC is meeting me every time. Just kidding. But I need to do some PIC courses, my knowledge in that area is very low. And all material that I find about PIC programming in the internet is very weak. Thanks

22nd June 2006, 08:15 PM	#12
Hero999	90% accuracy? Do you know that means? It means is can vary by 90% and you've not said whether it's +/- 90% or both. If a 1Hz oscillator has an accuracy of 90% that means it can drift between 1000 + 1000 * .9 and 1000 - 1000 * 9, that's a very big range! Are you sure you didn't mean 10%? __________________ I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong. Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.

23rd June 2006, 12:03 AM	#14
panic mode	so you want circuit that will stay stable within 9%, have adjustable frequency and duty cycle but not depend on each other? there are several ways to do it, you can try mcu, use oscillator followed by monostable or use sawtooth oscillator followed by comparator with adjustable preset but there are also CMOS or TTL solutions...