Qns on DC Power Supply

[eblc1388]

No fancy circuit. Just uA723 + 9 x 2N3055.

Voltage drop 0- 15A full load = 3mV.

 

[adrian22]

it is a project we r ask to do.

so are there any ideas can make some shortcut lik changing the compoent from D1, D2, D3 & D4 to bridge rectifier n thing lik tat?


Regards
Adrian

 

[eblc1388]

...lik changing the compoent from D1, D2, D3 & D4 to bridge rectifier n thing lik tat?

You can use a bridge rectifier for D1-D4. It is not a shortcut but an equivalent circuit. I can think of no other "shortcuts".

 

[adrian22]

is a projuect we r ask to do.

then is there any way to replace compoent to smaller the circuit lik changing to bridge rectifier(replace D1, D2, D3 & D4)?


Regards
Adrian

 

[adrian22]

i understand but the transformer given is 15-0-15V so is 15V 0V 15V but wat the wavefull after the D1 & D4 and D2 & D3?

is there any program can sim. the drawn circuit?


Regards
Adrian

 

[Sebi]

Small PS with CT trafo.

 

[adrian22]

so by changing the direction of the cap can inverse the voltage from +V to 0-V m i rite?





Regards
Adrian

 

[audioguru]

Adrian,
Look closely at how the rectifier diodes are connected. They determine the polarity of the rectified and filtered +20V and -20V that feed the regulators. The polarized 2200uF filter capacitors must be connected in the direction shown or they might explode.

The same for the 7815 and 7915 regulators. The 7815 positive regulator must be connected in the positive part of the circuit, and the 7915 negative regulator must be connected in the negative part of the circuit. :lol:

 

[Sebi]

The bridge rectifier with CT trafo - in this case - work as two independent two way rectifier: one pair diode with common cathode for +V out, another pair with common anode for -V out.

 

[adrian22]

Is this circuit a fullwave or a halfwave?

So are there any program which can draw n the diagram n measure voltage n waveform?


Regards
Adrian

 

[audioguru]

Full-wave.

 

[adrian22]

So 15V at the secondary wings given out an output of +15V, -15V, +15V, -15

is it? cos i not sure how the transformer work as i learn 2yrs back...

 

[audioguru]

No, A 15V-0V-15V secondary gives peak voltages of +21.2V, -21.2V, +21.2V and -21.2V at a little less than full load. A transformer's output voltage is higher with less load. The voltage regulators provide a regulated +15V and -15V. The regulators need at least 17V to 18V minimum input to function properly.

 

[adrian22]

so for the diagram



how it get the -V?

N is there any software can draw n see the the waveform n measure the voltage?


Regards
Adrian

 

[audioguru]

so for the diagram
how it get the -V?

When the top transformer terminal's voltage swings negative, then D2 conducts. When the bottom transformer terminal swings negative, then D3 conducts. Therefore it is full-wave.
Actually, since C3 is almost fully charged most of the time then D2 and D3 conduct only during the peak negative voltage of the transformer.

is there any software can draw n see the the waveform n measure the voltage?

I don't know about simulation software. I would just build the thing and look at its output on my oscilloscope. :lol:

 

[adrian22]

wow u have ur own oscilloscope.

by the way when the top wing at +V the bottom wing will be -V is it?

& how will u say identify the different sub-sections that make up the power supply on the schematics diagram? refer the diagram post.gif


Regards
Adrian

 

[audioguru]

wow u have ur own oscilloscope.

I made it from a kit when I was young, learned a lot with it and still use it every day, 40 years later.

by the way when the top wing at +V the bottom wing will be -V is it?

Yes, I am glad you understand.

how will u say identify the different sub-sections that make up the power supply on the schematics diagram? refer the diagram

You can identify the few sub-sections, but first you should fix the input to the primary of the transformer.

 

[adrian22]

So clever u hav made 1 oscilloscope up & can last so long wow u r really Electronics God.

Cos of ur clear info i m able to recap all those info is all by ur kind help.

As i m from singapore. i saw a fuse 13A use in all kind of electronics, so i tot it will b using a 13A fuse.

So after i hav change this 3 point the main cor. is on the circuit lik

1. D1 & D4 give a fullwave of +V & D2 & D3 give a -V of fullwave
2. cap C1 is smooth the +V waveform C2 is smooth -V waveform

thing lik tat so how will u say abt the circuit in sub-sections that make up the power supply

 

[eblc1388]

You have to be careful about part number..

 

[audioguru]

Good point, L. Chung. :lol:

BTW, where did those puny little "L" 100mA regulators come from?
If the 79L05 has a 100mA load then the 79L15 won't be able to supply -15V to a load.