What is the easiest way to drop voltage from 12 to 9vdc?

[0x00x0]

Hi all,

I have a device which puts out 12vdc 400ma when a remote button is pressed.

I want to hook up this device to a 4" electric bell, but the bell is rated at 4.5 to 9vdc or 8-16VAC. What would be the simplest safe way to drop the voltage into the recommended range? Would a simple 1/2 watt resistor work?

The transformer which was recommended for use with the bell is rated 16v, 10 watts

Thanks in advance!

 

[crutschow]

Can't tell you want value or wattage resistor to use untl you tell us the current draw of the bell.

 

[0x00x0]

the bell manufacturer recommends a 16v, 10 watt transformer. That would be about 0.625 amps max. the output of my device is 12 volts 400ma for 4 seconds each time the remote button is pressed.

I also wonder, I have 2 bells exactly the same, I would like to put one on each side of the house. Perhaps hooking them up together in series would give me the voltage drop to make it close to spec..

 

[saeediqkw]

Very easy just use 1 resistor one zener of desire voltage +0.6 and any transistor of desire current take out from emitter

 

[crutschow]

I also wonder, I have 2 bells exactly the same, I would like to put one on each side of the house. Perhaps hooking them up together in series would give me the voltage drop to make it close to spec..

Two bells in series would double the required voltage to 9V to 18V. I'm not sure what the DC bell current is since the value you gave me is for AC. But it will probably work with your 12V supply, 400mA supply.

 

[Tightwad]

I wouldn't think it would hurt to run a bell at 12v. Most 9v supplies are not that well regulated anyway.

 

[saeediqkw]

Dear Brother, bell rating is 4.5--to 9Volts so it will be better to provide 6 volts to the bell for the safty even you give 12volts may be the bell will not burn and it all depend on the design, if they put wattage of R, Zener (may be) less than the average (to make lcost low). Normally maximu rating is not recmended. why you want to make in series, maki in parrellel, Calculate the ohmic value of the bell and then you can calculate the current required by the bell...It will not take more than 120ma (max) as it operate on low voltage. this is the just answer 12 volts to 6 or any voltage converter.
I am using from last many years and reliable that you need
1. resistor 470--1k any one you have if use 470 ohm use 1 W or 1/2w (safe side).
2. Zener diode 1/2watt enough put resister and zener diode of 6.7 volts in series
3. Zener diode connect to the base of the transistor (for 2n3055 for upto5 AMP)
4 Collector of npn transistor connecto the power supply with resistor
5. take the output from the emitter of the npn

Advantage:
you will get the 6 volts, Secondly if there is short curcuit and you put the transistor with more current for example 1amp and your transformer provide 400ma. So as short will occur.....Transformer cannto provide more than 400 ma so base current will stop. and if you can calculate the resistor so the base current not increase more than 400ma
.

every thing will be the safe

 

[Willbe]

Hi all,

I have a device which puts out 12vdc 400ma when a remote button is pressed.

I want to hook up this device to a 4" electric bell, but the bell is rated at 4.5 to 9vdc or 8-16VAC. What would be the simplest safe way to drop the voltage into the recommended range? Would a simple 1/2 watt resistor work?

The transformer which was recommended for use with the bell is rated 16v, 10 watts

Thanks in advance!

If 1N400X diodes are cheaper than resistors, use 3 or 4 of them in series.

 

[Hero999]

A 7.5R 2W resistor will do.

 

[Demon-13]

test the 7809 IC.....

 

[Edd]

If the bells require 6V each and you want 2, hook them up in series to the 12V supply and 6V will drop on each. 4.5-9V rating sounds like a nominal 6V bell. This should also allow for any variation in resistance between the two bells, as even if they are vastly different, you probably don't get over 9V dropped on one bell.