Difference between revisions of "VW Electrics Smooth 12v/5v supply"

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'''Simple Power Supply'''
'''Simple Power Supply'''


These days, we run laptops and other items that need a smoother or even reduced supply compared to the nominal 12.5V supply, and if the engine is running, the voltage can reach 14v. A raw supply is fine for some items but most modern electronics require a bit more precision than this. For instance, 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 - LM7810.
These days, we run items that need a lower supply than 12.5V, and if you've got something that uses say 9v, although you could plug in an adapter, this isn't always ideal. You can get round this by making up a simple voltage dropper but for that you'll need a voltage regulator.




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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. Check the amp rating will be suitable for your appliance.
With the addition of a few capacitors to remove interference from other electrical items, 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. Check the amp rating will be suitable for your appliance though.


 
Heres a simple circuit using an LM7812 regulator (for reference only):
Heres a simple circuit using an LM7812 12v regulator (for 5v you'd substitute with an LM7805):


[[File:smoothed12vsupply.jpg]]
[[File:smoothed12vsupply.jpg]]


'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. I recently purchased a 12v notebook to make things simpler in the camper - no need for voltage increasers, and three components provide a perfect power source. These type of voltage regulators are less efficient when you're dropping from 12.5v to say 5v, as more is lost in heat (hence the need for a heatsink), but dropping your battery supply to just a fixed 12v is fine as the change is slight.  
'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
A great video explaining the principles can be found here: https://www.youtube.com/watch?v=GSzVs7_aW-Y

Revision as of 10:30, 23 December 2015

Covkid:

Simple Power Supply

These days, we run items that need a lower supply than 12.5V, and if you've got something that uses say 9v, although you could plug in an adapter, this isn't always ideal. You can get round this by making up a simple voltage dropper but for that you'll need a voltage regulator.


Relatively cheap, voltage regulators have three legs and in various ratings (see last two numbers) including but not limited to:

LM7805 (5v)

LM7809 (9v)

LM7810 (10v)

LM7812 (12v)


With the addition of a few capacitors to remove interference from other electrical items, 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. Check the amp rating will be suitable for your appliance though.

Heres a simple circuit using an LM7812 regulator (for reference only):

Smoothed12vsupply.jpg

'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


Mains Hookup Power Supply

If you really want to go to town on this, you can create a really good, stable little power supply on hookup (240v) from an old computer ATX power supply as follows: https://www.youtube.com/watch?v=z2oSFpKh_Uw https://www.youtube.com/watch?v=GSzVs7_aW-Y

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