How do I make 12v (car battery) into 4.5v

[mikysee]

I bought a Digital Car Compass with Time. It uses 3 AAA batteries as normal power source but I want to use the car battery to power it so I dont need to change the batteries. How would I make the circuit. What would I need from radio shack to make this work without setting my car on fire or frying the clock/compass?
Thanks in advance.

 

[Colt45]

voltage regulator IC, or sting of diodes, or zener + resistor, or, if you know the current it draws, and it is reaonable, then a resistor.

 

[Garion]

Radio Shack sells a 12-volt to universal DC adapter. You can adjust a switch that lets you pick between 3, 4.5, 6, and 9 volt output.

If the compass doesn't have a plug for external power, you can usually wire in the adapter into the battery compartment. Most batteries are run in serial, meaning there is a lead from the positive pole of battery #1 that goes into the device, Negative pole #1 touches positive of #2, negative of #2 touches positve of #3 and then the negative pole of battery #3 goes into the device. (Hopefully that's clear - Batteries go in line, + to -). It might not exactly look like that's how it works, but if you look at how the metal contacts work in the battery compartment, that's usually what happens.

If you can figure out which lead is positive and negative from the adapter, you can cut the wire and manually solder/wrap the leads to the right spots on the device to "fake out" a series of batteries. Works like a champ..

If you're hesitant to cut the power lead of the adapter and hard-wire that in, you can always get a female plug from Radio Shack that matches the male output of the adapter. Wire up some eletrical wire (speaker wire is usually fine) to that female plug and voila - Instant bare wires without cutting the original apart.

- G

 

[Heisenberg]

Originally posted by: Garion
Radio Shack sells a 12-volt to universal DC adapter. You can adjust a switch that lets you pick between 3, 4.5, 6, and 9 volt output.

If the compass doesn't have a plug for external power, you can usually wire in the adapter into the battery compartment. Most batteries are run in serial, meaning there is a lead from the positive pole of battery #1 that goes into the device, Negative pole #1 touches positive of #2, negative of #2 touches positve of #3 and then the negative pole of battery #3 goes into the device. (Hopefully that's clear - Batteries go in line, + to -). It might not exactly look like that's how it works, but if you look at how the metal contacts work in the battery compartment, that's usually what happens.

If you can figure out which lead is positive and negative from the adapter, you can cut the wire and manually solder/wrap the leads to the right spots on the device to "fake out" a series of batteries. Works like a champ..

If you're hesitant to cut the power lead of the adapter and hard-wire that in, you can always get a female plug from Radio Shack that matches the male output of the adapter. Wire up some eletrical wire (speaker wire is usually fine) to that female plug and voila - Instant bare wires without cutting the original apart.

- G

What he said.

 

[Jrdesmoke]

Well I was thinking the same thing but for different application and I thought of something to make it much easier you could always find and 5v car cell phone charger and plug it into the cigarette lighter or power out let and then just wire the device into it to recive 5 volts and a plus would be that it would only power on when the key is on.

 

[UsandThem]

 

[shortylickens]

Well I was thinking the same thing but for different application and I thought of something to make it much easier you could always find and 5v car cell phone charger and plug it into the cigarette lighter or power out let and then just wire the device into it to recive 5 volts and a plus would be that it would only power on when the key is on.

You literally did not read the thread.

Why?

 

[Jrdesmoke]

You literally did not read the thread.

Why?

Why did I not the man wants to be able to hook up a compass clock he requires 5 volts so you guys rather had the man go to RadioShack and go through all kinds of trouble to get something wired into his vehicle when the wire car charger at running behind the dash to hide The wire and get a a faster easier way to power his clock of 5 volts

 

[RLGL]

Why did I not the man wants to be able to hook up a compass clock he requires 5 volts so you guys rather had the man go to RadioShack and go through all kinds of trouble to get something wired into his vehicle when the wire car charger at running behind the dash to hide The wire and get a a faster easier way to power his clock of 5 volts

Did you not see the the OP is from 2004???

 

[brianmanahan]

I bought a Digital Car Compass with Time.

link isn't working, please update

 

[ultimatebob]

Why did I not the man wants to be able to hook up a compass clock he requires 5 volts so you guys rather had the man go to RadioShack and go through all kinds of trouble to get something wired into his vehicle when the wire car charger at running behind the dash to hide The wire and get a a faster easier way to power his clock of 5 volts

You would think that the sheer mention of Radio Shack would be a hint that this was an old topic. Didn't they all shut down about 5 years ago?

 

[Red Squirrel]

A 12v lead acid battery has 6 cells, which are around 2 volts each, so if you short out 4 cells you get a 4 volt battery. You can drive a couple lag bolts through the fill caps of 4 of the cells to do this.

Follow me for more unsafe battery tricks!