0-30 Vdc Stabilized Power Supply

[mohamnag]

Hi all,
can some one, specially circuit designer, give a complete part replacement?
new users (like me) can't read 70 pages?!

 

[audioguru2]

I have attached my recommended parts list for the improved version many times. Here it is again:

 

[MP1]

Hi all,
can some one, specially circuit designer, give a complete part replacement?
new users (like me) can't read 70 pages?!

The circuit designer's list is the one that is in the project. The designer has made no changes. The list above are modifications suggested by a forum member.

MP

 

[faizanbrohi]

I did not know about the changings , i bought all the parts that were written , and i have found them with the exact rating , so should i buy again ...  :-[

 

[audioguru2]

I did not know about the changings , i bought all the parts that were written , and i have found them with the exact rating , so should i buy again?

The 24VAC transformer is the most expensive part so keep it. Then the max voltage without ripple and with 3A load is about 24V. With a 3A load a 3A transformer is 41% overloaded since its output is rectified and filtered.

Replace the little 2N2219 that originally was Q2 with a real power transistor TIP31A with a real finned heatsink.
Replace the little rectifier diodes with a bridge rectifier module bolted to the metal chassis for cooling.
If the heatsink is big enough for the 2N3055 Q4 then since the voltage is low, second transistor in parallel won't be necessary.

 

[faizanbrohi]

Actually i live in pakistan , and it is so hot out here , and about 40 degress , pure sun on your head . although the sho is nearby but the roads are always jammed and the traffic is like nonsense . and the local busses are full . it is cruel out here . and i don't have enough budget now also , so can i work around with these components as well .

Please pray for the weather , it's hell out there.

 

[faizanbrohi]

By the way i have the 1N5408 instead of 5403 / 2 / 4 , it is a 3A Diode , and i got the TL081 , that i was suspecting , that i could not get

 

[faizanbrohi]

I am still suspecting if i can find TIP31A

 

[faizanbrohi]

By the way what is a trimmer potentiometer m is it a pot which can be mounted on a PCB . or something else , because i could not find it . instead i have a regular screwdriver resistor PCB mount.

 

[audioguru2]

Hi Faizan,

A 2SC1061 and hundreds of similar power transistors will work instead of a TIP31A. Maybe it is available in your country.

1N5408 diodes and any other 3A diodes will get extremely hot when the project has a 3A load.

The TL081 and most other opamps have an absolute max supply voltage rating of 36VDC. The project with your 24VAC transformer will have a supply voltage total of about 40VDC when it has low output current. A 741A opamp and a few others have a max supply voltage of 44V and the OPA445AP has a max supply voltage of 90V.

Your pcb mount screwdriver adjusted pot is a trimmer pot.

 

[faizanbrohi]

the 3A Diodes will heat , ok but will they overheat and burdown , i don't think so . ....

 

[audioguru2]

the 3A Diodes will heat , ok but will they overheat and burdown , i don't think so . ....

You are gambling.
Electronic parts are more reliable and last longer if they don't get hot.

 

[asciiwhite]

All attachments in this thread are now 0 bytes in size, did this happen since the merger of this thread?
I haven't followed this topic for sometime now...

 

[audioguru2]

This site was hacked recently. The administrator is trying to re-install the attachments from backup.
Is there anything that you need repeated?

 

[faizanbrohi]

Man why do they hack , what is the benefit

 

[faizanbrohi]

Why not use 2N2219 , why use TIP31A instead

 

[audioguru2]

If you have a perfect heatsink for a 2N2219 so that its case is held at 25 degrees C, then its max dissipation is only 3W when its internal temperature is at its max of 200 degrees C. A perfect heatsink is impossible so its max dissipation is only about 2W.

A 2N3055 output transistor has a minimum current gain of 25 with a collector current of 3A. So its max base current is 3A/25= 120mA. Its driver transistor will have 32V across it (24VAC transformer) when the project's output voltage is low, and 120mA through it which results in a dissipation of 3.84W. The 2N2219 will melt. A TIP31A can dissipate a max of 40W and will be fine with a little finned heatsink.

You might be able to use a 2N2219 if it has a very good heatsink with a fan, and select a 2N3055 for very high current gain.

 

[faizanbrohi]

ok you have a valid point , i will send some pics of my heat sink , so you can judge on that

 

[audioguru2]

A picture of a heatsink won't say much.
The heatsink's datasheet will say exactly how well it will cool.

 

[faizanbrohi]

see there is no heatsink here available with respect to datasheet. i have heatsink of a processor and one of some other device ,  by the way LM301 plastic  or LM101A metal op amp can also be used instead of LM741.