HELP! project abt DC power supply.

[infinity.o3]

helo, i new here. and oso new to electronic stuff.  i would like to ask how to build a power supply? it is a triple output power supply (o/p= +15v, -15v and -5v) of not more than 15 components. where can i find more about this stuff? any link? i would also want to find a schematic diagram of power supply. 

thank..!! 

 

[ante1]

Hi infinity,

Welcome to our forum,

Here are two circuits, one with fixed voltage and on with variable. To any of these you can add an LM 7905 on the negative side to get the -5V you require.

View attachment 37271

View attachment 37272

 

[infinity.o3]

thx.

i was wondering are there anymore simply diagram. i cant realli understand it.

 

[ante1]

Hi again,

Sorry but it don’t get much simpler than this, how can I help?

 

[infinity.o3]

i also ned to include resistor. but there are no resistor rite?
i still need to build a power supply out. hope u could help mi. =))

 

[SM2GXN]

Hi infinity.o3!

Going from left to right:

1. Marked 230 volts were the mains cable is to be connected, that side is called primary side.

2. F1 is a fuse 33mA/250 volts that one will blow if there is a short in the transformer windings or if there is to big load on the secondary side of the transformer which can be a faulty/shorted component. F1 is important!

3. Tr1 transformer with 230V primary and secondary 2X15volts/33mA center tapped meaning if you measure from centertap (line going in the middle marked GND=ground) to one of the outer taps you will get 15volts and if you measure across the outer taps 30 Volts AC.

3. D1-D4 As you correctly noted, diodes. These diodes will rectify the AC to DC, the two upper are for the positive/plus side and the lower diodes are negative/minus.

4. C1 & C2 are electrolytic capacitors these are filter capacitors, without them you will get an annoying hum. If you live in a country where the line frequency is 50Hz you'll get 100Hz hum and if 60Hz then 120Hz

5. IC1 & IC2 are voltage regulators they make sure that the voltage comming out from your power supply wont drop when you connect a load, they stabilize the voltage.
7815= 15 volts positive voltage regulator.
7915= 15 volts negative voltage regulator.

This power supply is for light loads meaning that you can't draw much current from it.

Bjorn

 

[ante1]

Hi infinity,

Just adding some to Bjorns detailed answer:
To your first question; there are no resistors needed in this circuit!
You can learn more about the voltage regulators here: http://www.aleeanne.org.uk/datasheets/datasheet2/LM7815.PDF
You can use the same circuit for heavier load by using a higher rated transformer and maybe slightly bigger caps if you need more current.
I don’t know where you live but it’s possible that you don’t have 230VAC mains but 120 VAC or perhaps something else.

 

[Kevin Weddle]

In another post long ago, I had this idea. A voltage multiplier, which is typically low current, makes a good DC source from an AC or analogue signal. Of course in order to make them high current, you need high capacitance. High capacitance makes them low voltage capacitors. Therefore, it is only impractical to take a high voltage source, use some capacitors and diodes, and realize a DC source. A transformer with capacitors and diodes is used in it's place.

 

[majorabak]

hey sorry... i m also new here... how abt the -5V output?
Where do i put it?

 

[ante1]

Hi Major,

Welcome to our forum.

Just add a 7905 to the negative side where the 7915 is.

 

[timothy1]

Hi ante,the electronics god!Just want to add on to the question.Do you mean adding 7905 beside the 7915?Then do i need to add space for the negative 5 output?Sorry for the trouble because i very new and blur to electronic stuff. Thanks ;D

 

[infinity.o3]

hey. sorry so long den reply. hee.

my teacher is giving mi LM7805. but at the circuit u gave is LM7915. is the two the same?

the fuse 33mA. why my teacher give is 1A?

C3, C4, C5 &C6 is wad? all is capactior? btw, my teacher onli will give us 3 capactitors.

 

[thefinalaeon]

hello infinity lol u from poly ar? wad poly? my teacher also ask me do same project as u for term break ahah...

 

[loVeheb3]

hi.... i am oso doing that project... i'm frm Tp... any here noe how to do the project pls tell mi thx..... n which is the schematics diagram?

 

[ante1]

Hi timothy,

You can do this one of two ways; either you connect the input of the 7905 to the input of the 7915 or to the output of the 7915. Then connect the ground pin of the 7905 to the 0v rail and last the output pin of the 7905 will be your -5V output. Add a capacitor on the input side as well as to the output side just like it has been done with the other regulators.

 

[infinity.o3]

hello infinity lol u from poly ar? wad poly? my teacher also ask me do same project as u for term break ahah...

eloo. i from tp. i bet u oso from tp. ;D
hv u finish ur project?
do u noe how to write 'the explanation on the operation of the power supply'?

 

[timothy1]

Thanks ante!hi everyone,i also from tp.I believe everyone is busily doing your EPT project.When you serch internet,there is no clue on the triple output supply and it goes the same for books.Any suggestion must post wor..

 

[st0rmagneto]

Hey !! Hi !! Same here , doing tt project .. If anyone of you had gotten the schematic diagram , please kindly email me at [email protected] .

Thanks !!

 

[thefinalaeon]

sian... me also from tp lor... i dunno how to do leh... i onli found the datasheet for the 4 components tts all... btw ante... u give us 7915 and 7905... our teacher give us 7815 and 7805... any diff btw them? please kindly help