Can someone please clear something about power supplies plzz

[barrymons]

I'm busy building a power supply that converts 220v to 12v dc. i use: 200va power supply that converts the 220v to 12v ac unregelated now i want to convert it to 12v dc so i use a 36 amp rectifyer for the dc part. Now can anyone plz tell me how i can and what parts to use to make it a 12v dc regulated power supply? and can i use this system for charging a 12v car battery when it is finished? thnx for the help guys

 

[Dr.EM]

Firstly be extremely careful with the mains electricity, especially if you are unsure of what your doing.

After the bridge you need a large suitable rated electrolytic capacitor to smooth the supply. However, once your 12vac is rectified and smoothed you will have the peak voltage at the output. This is 12v x the square root of 2. To lower this to 12v you can use a voltage regulator, but I would think a car battery will take a lot of current.

 

[barrymons]

yes

I have tried a smoothing cap a 2200uf 16v then when i put the meter on it gives me 14.something volts when i connect a 50w light it brings down the to 9 volts

 

[barrymons]

by the way

it is not a power supply if it matters it is a transformer... :wink:

 

[Russlk]

Your transformer is too small. To supply 36 amps at 12 volts, you should have a 500 VA transformer at least. It will be heavy. It is not necesary to filter the DC for battery charging.

 

[tkvenki]

Select a suitable current rating for transformer.
THen after the transformer use a Bridge( appropriate current rating).
After this bridge u can put the filter capacitor.
THen u can use a regulator. While using a regulator, make sure it is capable of sourcing the required current.

U can divide ur project into sections. and provide each section with a different regulator. Do not forget to put Heat-sink to the regulator.

 

[barrymons]

but

I dont want to use it just for battery charging the whole idea is for camping. all my light are 12v dc and then i want to connect them to the transformer without any problems aswell to the 12 v side if i dont have 220v availible i can hook it straight onto my battery..
thanx for the help guys

 

[Russlk]

The lights don't need filtering either, plus the battery will provide smooth DC if you want to run a radio, so all you need is the rectifier and perhaps a current limiting resistor.