hi m,
The diode type you have posted has this image, how do you intend connecting as a bridge across the CT transformer to give a +V out.?
E

 

im sorry im not so fluent in english but this is how i set it up, i will hook the 28v on each anode pins, and plus will be the cathode, and - will be the ct, exactly the image below

 

hi muno,
This is what I see , I am using an equivalent diode 100A ar 100Vreverse
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hi,
This is with the rectifier connected to the power supply.
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Green plot is power in TIP

 

im tryin my best to understand the graph and what would be the result, is it good or no? im sorry im totally noob

 

Hi,
The BLUE plot is the input voltage to the power supply.
With a 24Vout at a 3Amp load current, the BLUE averages about +36Vinput

The RED is the power supply output voltage 24V at 3A

The Green plot is the heat dissipation of the TIP at the above conditions, about 36Watt average.

Does this help.
Note the large C4 smoothing cap.

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Added 2nd image showing the OFF load conditions of those 3 above parameters

 

thank you very much for all the efforts you made. it really helps me specially im a beginner. i will download all your uploaded files and save it to my drive so that i can study them further more, its such a very nice work you made, i think im ready to build the circuit, and witness some smoke resulting from my mistakes, maybe... but thank you, its such a nice forum

 

by the way, the circuit will be using 1 piece of lm358, right?

 

hi m,
I assume you have a copy of the LM358 datasheet.? attached, it is a dual OPA.

Be aware of the additional heating if you set the Vout to +12V at 3Amps, the Green plot.
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im tryin my best to understand the graph and what would be the result, is it good or no? im sorry im totally noob

Hi Munro, I'm trading on eggshells here, but I'm really thinking that the best way to learn is step by step and I'm concerned that you are working with mains voltages here, where it's especially important to understand what's going on. The "sawtooth" waveforms are a consequence of voltage drop as the rectified AC is at low voltage and the 4700uF capacitor C4 is trying to maintain the peak voltage but dropping due to current being drawn. The bigger the current drawn, the bigger the voltage drop between (half) cycles - the bigger the capacitor the smaller the drop.

Dare I ask if you understand the rest of the circuit? A bench top supply is indeed an essential piece of equipment and I completely understand that you need one. For most of my needs I get by with an LM317 with a potentiometer to adjust the output voltage using an old 19V laptop power supply as the input. Really safe to play with and most of my projects need anything from 2V to 15V DC supply and well below 1.5A so I only use a small heatsink and rely on the LM317 thermal overload protection to limit the power. When you decide to build something that someone else has designed I highly recommend that you understand the purpose of every component part - the best way to learn, and it helps you to move on to adapting the ideas of others. I've only just joined this site and I've tried to contribute and have already learned a fair amount that I didn't know before! Good luck with your journey, sorry if I'm out of line, not meaning to offend.

 

hi m,
I assume you have a copy of the LM358 datasheet.? attached, it is a dual OPA.

Be aware of the additional heating if you set the Vout to +12V at 3Amps, the Green plot.
E
View attachment 275332View attachment 275332

ok noted. i have more transistors here like mjl21194, maybe it will help, i will providebigger heatsink,and fans

 

Hi Munro, I'm trading on eggshells here, but I'm really thinking that the best way to learn is step by step and I'm concerned that you are working with mains voltages here, where it's especially important to understand what's going on. The "sawtooth" waveforms are a consequence of voltage drop as the rectified AC is at low voltage and the 4700uF capacitor C4 is trying to maintain the peak voltage but dropping due to current being drawn. The bigger the current drawn, the bigger the voltage drop between (half) cycles - the bigger the capacitor the smaller the drop.

Dare I ask if you understand the rest of the circuit? A bench top supply is indeed an essential piece of equipment and I completely understand that you need one. For most of my needs I get by with an LM317 with a potentiometer to adjust the output voltage using an old 19V laptop power supply as the input. Really safe to play with and most of my projects need anything from 2V to 15V DC supply and well below 1.5A so I only use a small heatsink and rely on the LM317 thermal overload protection to limit the power. When you decide to build something that someone else has designed I highly recommend that you understand the purpose of every component part - the best way to learn, and it helps you to move on to adapting the ideas of others. I've only just joined this site and I've tried to contribute and have already learned a fair amount that I didn't know before! Good luck with your journey, sorry if I'm out of line, not meaning to offend.

i understand, yes i have lm317t, ive done a very simple circuit using that. but because i like to explore, i tried searching the web for an op amp with transistor power supply, and i came up with this circuit. as a beginnee, i loke discovering things, and yes, im aware that im working on high voltages. i do this just for hobby since im still studying. but , thank you, i really appreciate each and everyone of you

 

l

hi m,
I assume you have a copy of the LM358 datasheet.? attached, it is a dual OPA.

Be aware of the additional heating if you set the Vout to +12V at 3Amps, the Green plot.
E
View attachment 275332View attachment 275332

hi, i want to clarify again, d3 doesnt have series resistor? thanks

 

hi m,
Has someone told you should have a resistor.?
Where would you place it and what value.?
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hi m,
Has someone told you should have a resistor.?
Where would you place it and what value.?
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ive seen some circuit uses a resistor before zener, they say it limit current so that the zener will not fail, but maybe thats different cases. anyway, i dont have that d3(bzx84c12), what other value of zener can i use? thanks

 

hi muno,
Any 12Volt Zener diode will be OK, typical rated current say 5mA thru 20mA.

In your circuit, you can think of the LM358 as the 'resistor' that draws the current through the Zener.
The Zener drops the ~40Vdc down to ~28Vdc for the LM358, the capacitor helps to stabilize the 28V and also limits any noise injection into the LM358 power pin

E

 

hi m,
Please post the details of your transformer and its VA rating.
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my transformer is toroid type, 230VAC primary. 28-0-28 on the secondary, i think its 120VA, ive posted a more detailed here . a thread created by me

 

hi m,
Looking at that transformer, I would say it is only a 2.5Amp rating winding.

Do you know the gauge of the copper wire.?

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i can roughly measure at 1.03mm?