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Transformer 230/12V and buzzer

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kokosz

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Hello, i have problem with my transformer 230V/12V 20W max.
I want to reinforce buzzer 12V 5mA.
Can I make rectifier brigde with 4x rectifier diode 1000V 3A ?
Now back to the buzzer. I want to reinforce it with current from transformer. How to count value of resistor when the tension of transformer has 12V and buzzer is for 12V too and 5mA (0,005A). Can I conect resistor 0,25 W?
I know that is R = ( Ucc - Ub ) / I (Ucc - tension of transformer , Ub - tesnsion of buzzer) , but R = 0V (12V - 12V) / 0,005A. Here is a mistake.
Please can anybody help me? I can' t find this problem on the net.
 

You can rectify the 12V output of the transformer with 4 diodes, as you said, and also by adding a large electrolytic capacitor.
Bear in mind your output will be around 16V, in that case.

You cannot reinforce a buzzer, it was built to be as is. Shure, you can feed it a larger voltage, but no one can guarantee you the buzzer will withsatnd it, or at least for a long time.
 

Ok, but why in output will be 16V if the transformes make 12V ?
And if an accumulator has 12V voltage, how i should count value for resistor when i want to connect buzzer for 12v ? Which voltage ?
 

kokosz said:
Ok, but why in output will be 16V if the transformes make 12V ?
And if an accumulator has 12V voltage, how i should count value for resistor when i want to connect buzzer for 12v ? Which voltage ?
Click to expand...


Because, when talking about a transform, 12V means the rms (root mean square) voltage (Vrms), and after rectification you will approach peak voltage (Vp). These are related by:

Vp = 1.414 Vrms

If you have a 12V accumulator and a 12V buzzer just connect the buzzer to the accumulator, there is no need for resistor.

- - - Updated - - -

kokosz said:
Ok, but why in output will be 16V if the transformes make 12V ?
And if an accumulator has 12V voltage, how i should count value for resistor when i want to connect buzzer for 12v ? Which voltage ?
Click to expand...


Because, when talking about a transform, 12V means the rms (root mean square) voltage (Vrms), and after rectification you will approach peak voltage (Vp). These are related by:

Vp = 1.414 Vrms

If you have a 12V accumulator and a 12V buzzer just connect the buzzer to the accumulator, there is no need for resistor.
 

Can I change voltage from transformer to 12V (rms) ?
 

when we say the transformer which is 230V/12V, 12V is DC current
 

The Vp is 12V but i want to make 12V rms, HOW ?
 

Who can help me ? How to change 16V from transformator to 12V?
 

How to change 16V from transformator to 12V?
Click to expand...

Put a few diodes in the line. This will drop the supply V. About 0.6 V per diode.

The buzzer should be okay if you feed it 13 or 14 V.

You should not have to add a resistor in the line.
 

LED diodes? The diodes won't burn ?
 

I think you can regulate the voltage on 12v by a Zener Diode.
 

kokosz said:
LED diodes? The diodes won't burn ?
Click to expand...

I was thinking of silicon diodes as in this diagram:

97_1342556949.gif


But come to think of it, if you're only drawing 5 mA average, then you can in fact use an led. Typical safe limit for an led is 20 mA.

An ordinary red led will drop around 1.7 V. If you have different color led's then test them and you'll see they drop different amounts.
 

I want to connect buzzer and 1 red LED parallel to 12V
 

Quote Originally Posted by kokosz View Post
Ok, but why in output will be 16V if the transformes make 12V ?
And if an accumulator has 12V voltage, how i should count value for resistor when i want to connect buzzer for 12v ? Which voltage ?

Because, when talking about a transform, 12V means the rms (root mean square) voltage (Vrms), and after rectification you will approach peak voltage (Vp). These are related by:

Vp = 1.414 Vrms

If you have a 12V accumulator and a 12V buzzer just connect the buzzer to the accumulator, there is no need for resistor.
Click to expand...
Dear kokosz and etmabreu as you know Vrms = 12 v , however on the full bridge we have Vp= 1.414 Vrms - 2*.7(bridge diode voltage) = 16-1.4=14.4v
Now if you want to have a good power supply you should filter and stabilize it . you can use a 220uf capacitance and a 12v zener diode.
Remember Ac line maybe have some variation and if you use series of diode then you don't have a confident power supply over 12v.
I want to connect buzzer and 1 red LED parallel to 12V
Click to expand...
You should series LED by a 1k ohm resistor and parallel to your buzzer.
 
Last edited:

Can i connect after the beidge 1x zener diode to stabilisate voltage to about 12V. But which diode will be better? Zener 3,6 then there will be 12.4V or Zener 4,7 and then will be 11,3V ?
Should i put any resistor before the buzzer ?
To the picture : Why before diode is a resistor 1k? can I connect 450 Ohms ? R = (12V - 3V) / 0,05A R = 450 Ohms

Or I misunderstood effect of zener diode ? If i have zener diode 12V after that i will have 12V for example with 16V in source ?
 

You are overcomplicating a simple thing like connecting a buzzer to a DC source...
 

No, i want to know about a zener diode. I have one C4V7 4,7V 0,5W and i don' t know about voltage which is artef that. It will be 4,7 V after diode, or 16V - 4,7V = 11,3V ?
 

kokosz said:
Hello, i have problem with my transformer 230V/12V 20W max.
I want to reinforce buzzer 12V 5mA.
Can I make rectifier brigde with 4x rectifier diode 1000V 3A ?
Now back to the buzzer. I want to reinforce it with current from transformer. How to count value of resistor when the tension of transformer has 12V and buzzer is for 12V too and 5mA (0,005A). Can I conect resistor 0,25 W?
I know that is R = ( Ucc - Ub ) / I (Ucc - tension of transformer , Ub - tesnsion of buzzer) , but R = 0V (12V - 12V) / 0,005A. Here is a mistake.
Please can anybody help me? I can' t find this problem on the net.
Click to expand...

good grief
 

I' m seeing you can' t help me
 

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