12v regulator
Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=85714
Printed Date: April 25, 2024 at 12:55 PM
Topic: 12v regulator
Posted By: sarbein
Subject: 12v regulator
Date Posted: November 16, 2006 at 1:26 PM
hi all,
when i start my car the starter needs a lot of current to operate.So for 3-4 seconds,until the car starts normally,the voltage drops down to 0V and rises up to 12V very quickly because of inductive phenomenon.
I want to construct a voltage regulator 12v or 12,8v maximum input, to 12v output with 2A circuit current maximum.The circuit in normal operation demands 100mA.So ideal stable output is 12v/100mA!
This circuit will provide a small GPS modem..
if someone has a schematic circuit would help me a lot!!
thanks in advance..
Replies:
Posted By: kgerry
Date Posted: November 16, 2006 at 2:15 PM
go to an electronics wholesaler and ask for a 12 volt + v reg... but keep in mind that a regulator regulates it's supply voltage... so if supply drops out so will it's regulated output..... you may want to look at a gel cell battery or alarm backup battery ...... ------------- Kevin Gerry
Certified Electronics Technician
MECP First Class Installer
Owner/Installer
Classic Car Audio
since 1979
Posted By: sarbein
Date Posted: November 16, 2006 at 2:41 PM
thanks kgerry!!
Posted By: sarbein
Date Posted: November 16, 2006 at 4:03 PM
Just a moment kgerry
I agree that a regulator regulates it's supply voltage,but when the suplly drops out,this msec,can i use a capacitor with a large discharge constant in order to keep my output voltage to 12v?
Then the spike of 12V comes again and recharge my capacitor..this repeats 2-3sec until my car starts operating normally..
If i make a mistake please correct me.
Posted By: KPierson
Date Posted: November 16, 2006 at 5:18 PM
You're going to need a pretty large cap to supply a 100mA device at 12vdc for 4 seconds. I'm not sure why you need the voltage regulator at all though. Most voltage regulators will need ~+2vdc above their output to actually work correctly, meaning you will need about 14vdc constantly to provide a solid 12vdc out. I like the idea of using a small back up battery system. ------------- Kevin Pierson
Posted By: Ween
Date Posted: November 17, 2006 at 10:30 AM
hi, just use a diode (1N4001 or similar) on the power lead and a large value capacitor across the power leads of the device. used to have to do that with some older radar detectors to have them power up properly. i'd start with 10000 microfarads and go from there...shouldn't take up much space. hope this helps mark
Posted By: master5
Date Posted: November 17, 2006 at 11:25 AM
What kind of vehicle is this? Perhaps you need a better battery or starter? If this vehicle requires that much current to start and nothing is defective I would think the best way around is a small back up battery, isolated during crank. I would not trust a cap to perform this function although it might work as well. But the current demands for the small GPS modem seems like a prime candidate for a b/u battery in this case. I don't believe a regulator will do much if the voltage is actually dropping down to zero as you state, that is not really it's purpose. -------------
Posted By: master5
Date Posted: November 17, 2006 at 11:30 AM
Oh wait...you didn't mention, where are you measuring this "zero" volts? You might just need to connect the GPS to an ignition wire. If you have it on an ACC wire it will read zero during crank. That is normal. This may not be the problem but trying to check out all possibilities. "normally,the voltage drops down to 0V and rises up to 12V very quickly because of inductive phenomenon" I don't think this has anything to do with inductance, but if everything else is normal it is current draw issues. Good Luck -------------
Posted By: sarbein
Date Posted: November 18, 2006 at 3:59 AM
Thanks master5 for your reply!!!
I will try to use a detector (diode-capacitor)as ween said.
The problem is that i don't want to use a battery.Otherwise i wouldn't have problem because battery would save me during crank..
I hope that the combination 1n4001 and 10000ìF will work properly!!!
Thank you ALL!!! 
Posted By: master5
Date Posted: November 18, 2006 at 12:23 PM
Ok, keep us posted. Best of luck. -------------
Posted By: ainami
Date Posted: November 18, 2006 at 9:39 PM
Sarbein, in some cars it is normal that the voltage will drop to 0V when cranking the engine. This is to reserve and give the full power to the starter. To solve this you have run a wire between the starter input and gps input. So, when you crank the engine, you will "crank" the GPS also. Don't forget the diode in between or you could relay it. Good Luck
Posted By: master5
Date Posted: November 19, 2006 at 12:31 PM
If a vehicle dropping to zero volts during crank was "normal" you would have to reset the clock and radio memory every time you started the vehicle. Only connections to the ACCESSORY wire on the ignition harness go to zero volts during crank for the purpose mentioned above...but it is NOT normal for everything to go to zero during crank..well the vehicle would not even start if this happened..how would the ignition coil get 12v?
-------------
Posted By: 1lowgalant
Date Posted: November 19, 2006 at 1:09 PM
master5 is correct. if the entire vehicle is dropping to 0v during crank, you have electrical issues somewhere.
-------------
Whatever you do, DO NOT let the white smoke leak out of the wires.....
Posted By: electrostatic
Date Posted: November 19, 2006 at 1:26 PM
battery voltage shouldn't drop more than 1.5 volts during cranking. a car battery is almost completely depleted at 10 volts.
-------------
Prove your connections, use a meter!
I promise, I'll behave!
|