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0-30 Vdc Stabilized Power Supply
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Author Topic: 0-30 Vdc Stabilized Power Supply  (Read 320138 times)
rosana
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« Reply #1722 on: September 05, 2012, 06:58:58 PM »

but the mc 4071 doesn t have the same entrance like is showing on U2

i need to know how do ihave to connect the trimpot with the mc4071
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audioguru
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« Reply #1723 on: September 05, 2012, 08:01:20 PM »

It is [b ]NOT[/b ] an MC4071 which might be a Cmos quad 2-input OR logic gate with 14 legs.
Instead it is an MC34071 single opamp with 8 legs.
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mroy559
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« Reply #1724 on: September 19, 2012, 05:05:10 AM »

Somewhere with this topic, somebody said, that some capacitor should be changed through electrolytic in order to tantal as well as something. Attempt to browse somewhat.
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audioguru
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« Reply #1725 on: September 19, 2012, 08:44:38 AM »

Somewhere with this topic, somebody said, that some capacitor should be changed through electrolytic in order to tantal as well as something. Attempt to browse somewhat.
We talked about the 10uF electrolytic output capacitor having dielectric absorption which might cause the output voltage to rise when it is turned down and there is no load. We recommended using a poly type of capacitor to eliminate this problem.

I do not remember anybody talking about using a tantalum capacitor in this project.
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audioguru
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« Reply #1726 on: October 06, 2012, 08:34:46 AM »

I have made this supply but I am suffering with the problem of loading effect as am using it with very low ohms coil the output voltages get decrease with connection of load. My load resistance is not more than 12 ohms.

Please tell me what should I do to remove loading effect and get steady, constant output.
The improved circuit is designed to supply a maximum output current of 3.0A. It can be modified to supply 5.0A.
Ohm's Law calculates that 3A will flow in a resistance of only 12 ohms when the DC voltage is 36V. When the DC voltage is 30V then only 2.5A will flow so your project does not work properly.

The original project cannot supply 3A at 30V.
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audioguru
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« Reply #1727 on: October 09, 2012, 06:22:42 PM »

Can you tell me from where I can get improved circuit with 5A?
We talked about modifying this circuit for an output up to 30VDC at up to 5A DC a few years ago. It is the same circuit as the latest 3A circuit except the transformer produces more current (7.1A AC), there are three 2N3055 output transistors and R7 is 0.27 ohms at 10W.
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audioguru
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« Reply #1728 on: October 10, 2012, 07:49:50 AM »

This project uses AN OPAMP for its voltage regulation. Its typical DC voltage gain is 100,000 so if the output voltage drops only a tiny amount then it corrects it.
Its output voltage should not drop more than 0.03V when its load is increased from zero to 3A.

Maybe your project has wrong values in the current regulation section. The LED should not light when the voltage is being regulated but it should light to warn you that the current regulation is reducing the output voltage.
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audioguru
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« Reply #1729 on: October 12, 2012, 07:39:31 AM »

The original project used TL081 opamps and their total power supply voltage was higher than allowed. Then I changed the opamps to ones that are allowed the high supply voltage.

The original project used a transformer that was overloaded and its voltage was too low.
I changed it so it works perfectly.
What transformer are you using?

This project has the driver and output transistors inside the negative feedback loop of the voltage regulating opamp so the voltage regulation is excellent.
But you said that you added "a pair of 2N3055 as voltage follower" that are not needed and might ruin the voltage regulation.
Please post your schematic.
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audioguru
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« Reply #1730 on: October 13, 2012, 08:23:37 AM »

also, may I use 2n3055 as Darlington pair?
The fixed and modified 3A version of this project uses two 2N3055 output transistors in parallel to share the heat. The 5A version uses three paralleled 2N3055 output transistors. Each 2N3055 transistor has a series emitter resistor so the transistors share the current. They are driven by a BD139 little power transistor Q2 making a darlington pair. The first transistor in a darlington pair uses a fairly low current. The original version used an old 2N2219 transistor for Q2 that got too hot and was not designed for a good heatsink.

If you use a 2N3055 transistor for Q2 then the circuit might oscillate because a 2N3055 transistor is very slow.
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redwire
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« Reply #1731 on: October 16, 2012, 07:56:04 PM »

hi piyushghumelia,     I wonder if you really hooked this up in real world.    The diagram does not show any connections to sample the voltage of the  power supply and the code provided does not show any computations to  determine voltage or current. The diagram looks like a generic LCD hookup to a PIC.
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redwire
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« Reply #1732 on: October 17, 2012, 09:54:17 PM »

Sorry, not familiar with PIC
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mjvision
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« Reply #1733 on: November 07, 2012, 02:42:31 PM »

Hi!

In this modified version (http://diyfan.blogspot.com.br/2012/02/adjustable-lab-power-supply.html) he seems to have some good points. But why has he stripped audioguys two 3055 to only one 3055 and no emitter resistor?
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mjvision
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« Reply #1734 on: November 07, 2012, 02:52:14 PM »

Buggy forum... When I posted my first post, 24 new pages appeared.
I placed an order on components today, can you please say if there is any changes in this projects design in the last 24 pages?
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audioguru
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« Reply #1735 on: November 07, 2012, 05:09:37 PM »

But why has he stripped audioguys two 3055 to only one 3055 and no emitter resistor?
He must be using liquid nitrogen and a huge fan to cool his single 2N3055 transistor.

Quote
can you please say if there is any changes in this projects design in the last 24 pages?
Some people said that the output voltage does not drop to zero volts when there was an voltage then the voltage was reduced. It is because the electrolytic output capacitor C7 has "dielectric absorption".
They changed the capacitor to a film type that fixed the problem. A 10uF film capacitor is frequently used in a speaker crossover network.   
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