# Thread: 12v Regulator Schematic (15A)

1. ## 12v Regulator Schematic (15A)

Well I dont know much about electronics so I asked a friend of mine to make me a 12v regulator. Please do not ask me about it since I have no idea about those kind of things. However, I wasn't able to find a decent schematic of a 12v regulator so here it is. The Voltage on the car must be over 12.8 to supply a regulated 12V but the nice thing is that it is 15A and with a fuse can be lowered to 5A. He said that the components are cheap and not hard to find. He uses a so called "zener" which I havent got any idea what it is!

I am interested in your comments since you know more about this stuff. I know this isnt the BEST regulator available but it is a simple solution that I wanted to find and never did. Hope that it will be usefull to you all.

Thanx

2. unfortunitly a car's input would be anywhere from 8-16v but those are extremes

3. Yes I know........well at least in my 18year old car the input never drops lower than 10 except when I turn the ignition on. Moreover, once the engine is running it never drops lower than 13.4. Extreems are extreems though. Like when thunder hits your car! Thats also extreem

4. Yup thats fine, as you said keep the voltage higher than 12V.

The 12.7V zener diode is there to regulate the voltage across the base of the transistor at 12.7V. You will have a 0.7V drop on the emitter, so your final output is 12V.

You cant just buy a 12.7V zener diode, as they normally come as 11,12,13V...etc. Quick solution is to use a 12V zener and stick in another diode such as the 1N4148 this will drop the voltage by other 0.7V so your total = 12.7V You can use 13V but you end up with 12.3V on your final output.

The capacitors are just there to smooth out noise/spikes/dips and whatever. A small smoothing capacitor is typically required across the zener diode though.

For 15A rating the transitor dont have enough current gain, you will need to add a small NPN transistor connected as darlington paired with the 2N3005.

LOL what did you want to know anyway

5. Thanx for that! Nice to know that I am in the right direction!

6. EDIT :

opss no..not exactly fine, ask your friend to test it out anyway

You might find that useful :

http://www.the-cool-book-shop.com/fr...nics_guide.pdf

7. Now this is the updated schematic with the 12V zener.

8. I think you reversed the new diode you added.

--Tom

9. Nah, it's the right way around. You want the forward voltage drop across the diode to add to the zener voltage.

Rob

10. I am still stuck on the part about thunder hitting your car...

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