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Power Supplies

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Kane2oo2

New Member
Hi
Where is the best place to find/buy bench top power supplies?

and at around what price (UK)

would prefer to have a power supply rather than keep using 9v batteries :p

Kane
 

pike

Member
have a scavenge around your friends or neighbours they are bound to have and old computer. The computer has a power supply inside that can supply 5 and 12 volt rails at very high currents.
 

Kane2oo2

New Member
good plan!! :lol:

then all i need is a few different regulators to supply 9v and 6v
what current rated ones should i use?
(as you said they can supply very large currents!)

Thanks
Kane
 

Ravi

Member
Kane, It depends on your requirements. You may either use fixed or variable voltage type, 3 terminal regulators.Example,if you use a fixed regulator such as 7809, the out put current is limited to 1amp.On the other hand, a variable voltage regulator such as LM338K, you will be able to get voltages down from 1.2 to 32v max depending on you input voltage with a maximum current of 5amp. The LM 396K with voltages from 1.2 to 15v and a current of 10amp max. In high current applications it is essential to provide adequate heat sinking. Failure to observe this precaution may result in premature current limiting or output voltage foldback due to thermal shutdown.

Cheers!
 

Kane2oo2

New Member
ah ....it seems i understood wrong

i thought that because the power supply could give out that current...the regulator would use that current :oops:

so i think i shall have a number of fixed 1A regulators

Thanks alot
Kane
 

Kane2oo2

New Member
what is the difference between a 1amp regulator and a 0.1A (apart from the obvious)

but why would a 0.1A be used in place of a 1A one?

is there any other reason apart from price?

Kane
 

bmcculla

New Member
You can get a .1A regulator in much smaller packages. For example you could find a .1A reg in a TO-92 (or tiny SOT-23) package instead of the larger TO-220 for a 1A.

For a hobbiest there really is no reason to use a smaller current rating.

Another important thing to keep in mind when selecting a regualtor is the power dissipation. If you want a 3.3V supply regulated from a 12V supply at 1 Amp that is (12V-3.3V)*1A = 8.7W which is quite a bit of power to disipate in your regulator. 8.7W will reqire a fair sized heat sink on a TO-220 package or better. So don't just trust the current rating.

Hope this helps.

Brent
 
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