VW Electrics Smooth 12v/5v supply

Covkid:

These days, we run laptops and other items that need a smoother or even reduced supply compared to the nominal 12.5V supply, particularly if the engine is running when the voltage can reach 14v. A raw supply is fine for some items but most modern electronics require a bit more precision than this. The dash clocks in a T25 use a fixed 10v regulated supply for part of the circuit and this is achieved by a voltage regulator fixed to the back of the clocks rated at 10v.

Relatively cheap, voltage regulators have three legs and in various sizes including but not limited to:

LM7805 (5v) LM7809 (9v) LM7812 (12v)

With the addition of a few capacitors to further smooth out the supply, you can build a simple and effective power source at one or more voltage levels. They're cheap and easy to build and a whole lot less than ones you can buy - even on ebay.

Heres a summary of the circuit using a 12v regulator (for 5v you'd substitute with an LM7805):

'Input' refers to red wire from battery or other dash 12v power lead, 'output' to the item that needs the fixed supply. Earth (chassis) is common to both.

A great video explaining the principles can be found here:

https://www.youtube.com/watch?v=GSzVs7_aW-Y