Car 12v to 4.5v resistor circuit needed for low current devi

What resistor circuit is needed for a low current trafic alert device
which can be plugged into the courtesy light?
The traffic alert normally runs on 3 AAA batteries, but a terminal has
corroded off... }:-(

Happy with a soldering iron and vero board

cheers
Richard

 

[Harold Ryan]

Attach a 1 kohm resistor between 12 volts and the device you want to power.
Measure the voltage at the device. If the voltage is below, decrease the
resistor until you obtain 4.5 volts. Now add a 4.5 volt zener diode because
the vehicle voltage can vary from 7 up to 15 volts.

Harold


<richard.dykes@gmail.com> wrote in message
news:1130881504.995869.130800@z14g2000cwz.googlegroups.com...

What resistor circuit is needed for a low current trafic alert device
which can be plugged into the courtesy light?
The traffic alert normally runs on 3 AAA batteries, but a terminal has
corroded off... }:-(

Happy with a soldering iron and vero board

cheers
Richard

 

[gladholm]

Thanks for that and other info have helped cheers

 

[gladholm]

Thanks for that and other info have helped cheers

 

[lee]

put a 1W 7volt zener in series, no resistor needed....

 

[John Fields]

On Tue, 08 Nov 2005 01:36:31 GMT, "lee" <drennie@cfl.rr.com> wrote:

put a 1W 7volt zener in series, no resistor needed....

---
Really?

First of all, you can't get a 7V Zener, and, what will happen if the
input voltage goes up to 13.8V or you wind up with a 60V transient
on the line?

--
John Fields
Professional Circuit Designer

 

[Rich Grise]

On Tue, 01 Nov 2005 13:45:05 -0800, richard.dykes wrote:

What resistor circuit is needed for a low current trafic alert device
which can be plugged into the courtesy light?
The traffic alert normally runs on 3 AAA batteries, but a terminal has
corroded off... }:-(

Happy with a soldering iron and vero board

You shouldn't need much:
http://www.radioshack.com/product/index.jsp?parentPage=search&cp=&productId=2103679&kw=dc+power+adapter&tab=techSpecs

Or, you could use a hash choke, a transzorb, and a regulator to do pretty
much the same thing. ;-)

Cheers!
Rich

 

[John Fields]

On Tue, 08 Nov 2005 18:47:55 GMT, Rich Grise <rich@example.net>
wrote:

Or, you could use a hash choke, a transzorb, and a regulator to do pretty
much the same thing. ;-)

---
Hash choke... mmmmmm...

--
John Fields
Professional Circuit Designer