I need some simple circuit design help.

[4AGZE4EVER 10+ year member]

I need to step down 12ishv dc to 9ish v dc. Any body have a simple way of doing this? I want to hard wire my xm roady and the only thing left is the power. It takes 9v in.

Please help. I know that cars range form 12 to 14.4 v DC but the adapter says 12 v to 9 v.

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[lilmaniac2 5,000+ posts]

u need resisters to do it.... i dont remember the exact ohm load to drop 3 volts bah.. 2 years ago i couldve done this in my head lol

 

[JimJ 5,000+ posts]

Or a voltage regulator...would be a less "lossy" way of doing it.

Google for voltage step-down circuits?

 

[vladd 10+ year member]

are you sure you need a 9v in and that 12v won't work?

 

[JimJ 5,000+ posts]

http://www.maxim-ic.com/appnotes.cfm/appnote_number/1810

 

[4AGZE4EVER 10+ year member]

12v may work but I figured I ould play it on the sasfe side and just go for what the dc adapter puts out. I am going to put a meter on it tomorrow.

 

[ngsm13 5,000+ posts]

I need to step down 12ishv dc to 9ish v dc. Any body have a simple way of doing this? I want to hard wire my xm roady and the only thing left is the power. It takes 9v in.
Please help. I know that cars range form 12 to 14.4 v DC but the adapter says 12 v to 9 v.

Just use the cigarette lighter end, leave it on. Dismantle is, solder a positive lead and negative lead on the shit inside... and wire it in to 12v.

Easy as hell...

Or just buy this... you'll get better reception as well. It'll still be FM Modulated...but it will be hardwired. It also includes a female cigaretter lighter end with bare wire leads so you don't have to modify the power lead to hardwire it.

http://www.circuitcity.com/ssm/Delphi-XM-SKYFi-SKYFi2-Radio-FM-Modulator-SA10003-/sem/rpsm/oid/70756/catOid/-14641/rpem/ccd/productDetail.do

Tits!

nG

 

[JimJ 5,000+ posts]

FM modulation //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif

 

[ngsm13 5,000+ posts]

FM modulation //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif

That's the only way to do Satellite Radio unless you buy an aftermarket HU that is Satellite Radio Ready //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif.

nG

 

[Vestax 10+ year member]

Just use the cigarette lighter end, leave it on. Dismantle is, solder a positive lead and negative lead on the shit inside... and wire it in to 12v.

I agree, rather than wasting time fabricating something to drop voltage, use the existing cig lighter and hardwire it to your car. BTW, what car is it?

 

[qtipextra 5,000+ posts]

^^^ But then its is still too high when the car is running. Sure, 2.5 V difference probly wont hurt it, but most circuitry these days will not power on at a voltage much higher then the specified voltage.

 

[djman37 5,000+ posts]

^^^ But then its is still too high when the car is running. Sure, 2.5 V difference probly wont hurt it, but most circuitry these days will not power on at a voltage much higher then the specified voltage.

If it comes with a cig. lighter attachment that plugs straight into the unit, it can handle typical car voltages meaining it's regulated inside. Hardwire it, but BE SURE TO USE THE FUSE outta the cig. lighter attachment!

 

[Shyne151 10+ year member]

If it comes with a cig. lighter attachment that plugs straight into the unit, it can handle typical car voltages meaining it's regulated inside. Hardwire it, but BE SURE TO USE THE FUSE outta the cig. lighter attachment!

You sir are right.

For hardwire dsr's just get the kit posted above when it comes to xm... but if it's sirius just chop the end off.

 

[qtipextra 5,000+ posts]

Okay, I didnt know it came with a cigarette lighter adapter. Yea, just hard wire it using the cigarrette lighter adapter.

 

[4AGZE4EVER 10+ year member]

OK. I will never use FM modulation it blows goats. I am using RCA's to go to a aux-in.

on to other issues.

I tested the adapter it outputs 6 volt constant. This is regardless if the car is on (14ish) or off (12ish.) I openned it up and there is farely complicated looking circuit inside(at least to me.) I am just going to solder leads to the inside of it where it would normally plug in to the cigarete lighter. I'll take some pics tonight of the inside.