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Posted (edited)

↑ they have to fit widescreen cctv to fit the punters on the screen

Edited by MrHappy

Mr th2.jpg Veritas God

Posted
50 minutes ago, MrHappy said:

↑ they have to fit widescreen cctv to fit the punters on the screen

 

Haha, catch them stealing the cream doughnuts! 

 

I may have a go at vacuum forming my own bell box cover, to fit around a CQR MultiBox. Is the MultiBox any good? Anybody use them?  If they are ****, ill just design my own circuitry :-) 

Posted
34 minutes ago, james.wilson said:

I rate the multi box sia uses them but only the g3 one

 

Okay, I have seen the ones with two piezo sounders in them. Do you have any idea how they are driven? Had an old Ventcroft Classic PCB from 1996 connected to my oscilloscope, and it is reading a very high voltage, I am assuming that it is done from the transformer on the board? Interesting waveform, it was  moving in a very ordered pattern 

 

image.png.140bf610f2675589147221c583fba720.png

Posted
15 minutes ago, Gabs said:

 

Okay, I have seen the ones with two piezo sounders in them. Do you have any idea how they are driven? Had an old Ventcroft Classic PCB from 1996 connected to my oscilloscope, and it is reading a very high voltage, I am assuming that it is done from the transformer on the board? Interesting waveform, it was  moving in a very ordered pattern 

 

image.png.140bf610f2675589147221c583fba720.png

I think we need to clone you

Posted

Typical driver for a piezo. You'll find many examples on-line. The waveform is probably a warble or the like.  I'd suggest getting a copy of Horowitz & Hill 'the art of electronics' it's an excellent reference.

  • Like 1
Posted
11 minutes ago, james.wilson said:

Piezo needs high voltage old school mylar cone speakers need less but require more power. I prefered the lower freq as it gives more range but looks worse on spec sheets at 1m

By lower spec do you mean quieter? I would love to get my hands on one of the Lynteck sirens typically found in the bell boxes of the late 80s, or early 90s. Everyone had them. They are 118 dB, and make a distinct sound, any idea how they work? https://www.lynteck.co.uk/products/intruder/sounders/LY02-009-17.php these, I bet they have some sort of custom IC. 

 

16 minutes ago, GalaxyGuy said:

Typical driver for a piezo. You'll find many examples on-line. The waveform is probably a warble or the like.  I'd suggest getting a copy of Horowitz & Hill 'the art of electronics' it's an excellent reference.

 

I will have a look online, I have seen a few,  but I'm not sure if they are meant to drive something as loud as what I am after, although all I may need to do is ramp up the voltage to get the volume to increase 

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