Zener diode

[kwame]

Hi
folks i have bought a door bell to replace my automobile horn ( that consumes too much current) for my prototype alarm system.The door bell uses an input voltage of 4.5VDC.The transformer presently i have uses 12VDC .
I have read that a zener diode can be wire in series used to limit the voltage to 4.5V.There is very little information on the net about how to achieve this end.
Has anybody ever tried hands at the zener diodes?I need a little help.

 

[Sceadwian]

You may want to search again, for two reasons, one zeners are never wired in series with a load, and two there are TONS of easy to find references on how zener regulators work. Simply do a Google search for Zener regulator.

 

[colin55]

You really have to determine the EXACT voltages you are dealing with.
If the voltages are exactly 12v and 4.5v, just put a 6v8 and a signal diode in series between the voltages and a load resistor and a 100u. You will need a circuit diagram to show how the dioides are placed.

 

[Sceadwian]

Voltage isn't the only thing that's important, current (hence power dissipation) is critical.

 

[kwame]

the current is about 1000 miliamps

 

[colin55]

What doorbell uses 1AMP!

 

[Sceadwian]

I would suspect an automobile horn would draw that much, certainly not a door bell! Keep in mind regulating the voltage down is burning the power off as straight heat, so even if the bell uses 1/3 the current of the original horn it will still be dissipating the same amount of power because 2/3rds is wasted as heat, it's a lose lose situation.

 

[ronv]

Regulator

Could be the "ding" takes 1 amp, the "dong" is probably free.

Maybe a 7805 regulator would work better. If it doesn't chime to often it might not need a heatsink

 

[kwame]

Amps

The amps is actually 20 mAMps.

 

[colin55]

If the voltages are exactly 12v and 4.5v, just put a 6v8 and a signal diode in series between the voltages and a load resistor and a 100u.