Activate transistor with piezo disc

[duke37]

You could try a low voltage zener diode.
I think the transistor junction is prefered since it has a lower capacitance and so will output at higher frequencies. Here you only want audio frequencies.

 

[GPG]

Different mechanisms.
http://www.lumerink.com/courses/ECE310/f11/Docs/Junction Breakdown.pdf

 

[GPG]

You could try this, Connect D1 anode to 9V. Connect C6 neg terminal to 555 pin3. This will jack up the voltage to the transistor. Add a protection diode across C6 You may have to play with the timing and R4 to get what you want.

 

[CDRIVE]

You could try this, Connect D1 anode to 9V. Connect C6 neg terminal to 555 pin3. This will jack up the voltage to the transistor. Add a protection diode across C6 You may have to play with the timing and R4 to get what you want.

The Out pin of a TLC555 is only a few 10ths of a volt lower than Vdd. So I don't see any benefit in that configuration. ...Perhaps I'm missing something?

Cheers,
Chris

 

[GPG]

The Out pin of a TLC555 is only a few 10ths of a volt lower than Vdd. So I don't see any benefit in that configuration. ...Perhaps I'm missing something?

Cheers,
Chris

The cap will be charged to ~9v and when the output of t C555 goes high it will add another ~9v until the cap discharges. Hence the comment about timings.
The timer output will have to remain high for the duration of the noise signal which is controlled by C6 R4. And there is the possibility that C4 may end with a small reverse voltage at part of the cycle hence protection diode.

 

[CDRIVE]

If the circuit is modified as you suggest: When pin3 is high the neg leg of C6 will be nearly at the same potential as V+ (9V) less the voltage drop (0.7V) of D1. Hence C6 will be close to 0V. When pin3 goes low C6 is charged to V+ - 0.7V of D1 = +8.3V. I still don't see any benefit here.

You seem to think that what you described constitutes a voltage doubler but I'm sorry to say that I don't see it. Maybe I'm loosing it in my old age.

Cheers,
Chris

 

[GPG]

Initial condition pin3 low

 

[CDRIVE]

Initial condition pin3 low

Uh yeah but I still don't see how that changes anything. What you describe causes loss of the 0V baseline but does not change the PP output value. I'm sure that Drottson needs the output to swing to 0V when pin3 goes low. I suggest that you sim & post the plot results.

Cheers,
Chris

 

[GPG]

OK Red pin3 (simulated), Green cap +, Veb 9V (estimated) If the current does not go to zero add a diode forward biased to the transistor or the cap charging diode.. Be good to have the voltage that the transistor breaks down at.

 

[CDRIVE]

Please provide the schematic along with the sim but remember that Q1 Emitter must see a voltage between 0V (noise off) and +Vn (noise on). +Vn must rise fast but decay slowly. Drottson didn't specify how slowly but he seems to be content with the current value of C6 as it discharges through Q1 only.

On another note, this may be an exercise in self satisfaction of proving a point, because Drottson hasn't complained about lack of noise output. High battery drain is his most recent glitch. Not to say that this is a waste of time, as we are a tech forum where the battle of grey matter is always stimulating.

Thanks,
Chris

 

[GPG]

Q1 Emitter must see a voltage between 0V (noise off)

It only has to drop to a little less than the avalanche voltage which I suspect is close to 9V. hence only operates on a new battery until it reaches the flatter part of the discharge curve resulting in no noise, Some input from OP would help.What voltage across the be junction when it is producing noise. What battery voltage does it quit at??
http://cr4.globalspec.com/thread/72501

 

[GPG]

. When I hook it up to my DC power supply and set it a bit above 9V it works well all the time.

https://www.google.co.nz/search?q=9...Y_sYFrD7M:&usg=__dAZ0LBzKLYSfpx1HqC6MMpLFlFw=

 

[CDRIVE]

I took a spill off my bike. Suffering from severe skin loss and collar bone trauma. Typing is painful!

That said you'll be happy to know I now get it. You're right! Drottson only needs to bring that voltage down below avalanche breakdown of Q1. Good thinking!

Cheers,
Chris

 

[GPG]

Need dottson to implement and report.
Have just stopped riding a bike too many injuries incl broken mandible. Too old for that s**t

 

[Martaine2005]

I took a spill off my bike

Hope you didn't spill the grapes too!

Martin

 

[CDRIVE]

Need dottson to implement and report.
Have just stopped riding a bike too many injuries incl broken mandible. Too old for that s**t

Can't do that. I love it too much. Cycling has transformed me from a 265lb gelatinous mass to a 69 year old stud muffin. Women from 20 to 80 hit on me damn near daily ..and I love it. My wife ain't too thrilled about it though.

Hope you didn't spill the grapes too!

Martin

No, I drank them thinking they would help me sleep last night. It didn't work. It was a torturous night. I felt like I was laying on 20 grit sandpaper. I'm just as sick over the wounds on my new Trek!

Not too cheery,
Chris

 

[Martaine2005]

I'm just as sick over the wounds on my new Trek!

What is worse?
THIS OR THIS

SOooo, stay away from the 20 somethings....

 

[CDRIVE]

I don't know if UK TV has as many miracle pill and exercise commercials as we do but you know how they depict the before and after photos? Well check these out. The first one was taken just after purchasing my Trek Pure. The second one was taken last summer. So as you can see.. I ain't goin back!

Cheers,
Chris

 

[Drottson]

Sorry for the lack of progress, I haven't had time to work on the circuit for a while but I will definately try this as soon as I can get my hands on some other transistors.

 

[CDRIVE]

Sorry for the lack of progress, I haven't had time to work on the circuit for a while but I will definately try this as soon as I can get my hands on some other transistors.

Not a problem. We at EP manage to entertain and tweak each others dendrites with or without the OP.

Cheers,
Chris