cap on buzzer

[ILCML]

I've got a simple control box for a gate arm, adn there's an alarm buzzer. It's a 24v standard issue black, maybe 2" diameter 100dB or so buzzer. Question is, why is there a 470mF cap across it?

 

[itsmoked]

I'm not sure. 470mF is HUGE!!

Is it the size of a half gallon of milk? If not please look closer and see if it is 470uF or .47uF or .047uF or 470pF. These would make way more sense.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[OperaHouse]

The capacitor is to reduce the amount of radio frequencies generated that interfere with radio and TV reception in the immediate area. I assume this is an electrmechanical type.

 

[ILCML]

oops, sorry, yes, uF! 35v

so you think it's probly a filter?

 

[Skogsgurra]

Not nF? A 470 uF capacitor doesn't work well as an EMI suppressor. It usually has too high an internal impedance at HF for that.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[ILCML]

I thnk it was used to bump up the voltage a little (it was on the output of a FW rectifier) tomake the buzzer louder.

 

[Skogsgurra]

That is obvious - if you know about the full wave rectifier. A smoothing capacitor. And, yes, 470 uF would be a typical value.

Why did you ask if you knew the answer? Quiz departmant?

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[ILCML]

that was a guess...I assumed the cap would charge up to the peak value of the lumpy dc and provide the buzzer with a little more power....

 

[Comcokid]

Electromechanical buzzers produce a lot of low frequency EMI hash. In cars they can create problems with speakers and AM radios.

However, if the 'buzzer' is really a piezo-type, then a 470uF would cause it to beep a little longer when pulsed. A quick 'chirp' would turn into a very short beep.