Zener questions

[ehsjr]

On Aug 20, 12:30 am, gearhead <[email protected]> wrote:

[snip]

my friend showed me a circuit and wants me to duplicate
it. The schematic
is as follows:

Q1 10W
2N3055 0.1 ohm
Vunreg (42V) ___ Vout (24V)
o-----------------o---o----------- ------|___|----o---o------o
| | \ ^ | |
| | --- | .-.
| | | +----+ | |
| o------- --+ | | |2k2
.-. | \ ^ mje3055t | '-'
| | | --- Q2 .-. |
4k7 | | | | | | |
'-' +--- --+ | | 1k |
| \ ^ mje3055t '-' |
| --- Q3 | |
| | || | |
+----------+--------o-----||--+ | |
| \| || | .-. |
| mje3055t |-------o------->| | |
| Q4 <| | |1k | I=5mA
| | '-' |
|+ I=4.26mA | | |
=== o----------------------------+
/-\ | |
| | .-.
| z | |
| 1N5342B x 2 A | |1k5
| 13.6V 5W | '-'
| | I=10mA |
| === |
=== GND ===
GND GND

(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

[snip]

Who designed that, the Geico caveman?
Probably not, 'cause he would have done a better job.
Check out the design in this next link
and consider how in its simplicity and rationality
it contrasts to your friend's circuit:

http://www.rason.org/Projects/discreg/discreg.htm

The following link explains some of the basics
about linear voltage regulating. You should read
a little bit before you jump into anything.

http://www.national.com/appinfo/power/files/f4.pdf-Hide quoted text -

- Show quoted text -

Hi gearhead,

I just found another design similar to my friend's. What do you think
about it ? Is it more efficient? Is it ok to let the 7812 which is
rated at 1A to work at 866mA?

Allen

You can use the technique shown in that, but you really
need to scrap the schematic and start from scratch. The
one your link shows is totally inadequate for your 60A
requirement.

Start at the input. Your transformer will need to be
capable of providing over 100 amps at the secondary
if you want a 60 amp supply. Your rectifier will
need to be rated to handle that. That's two expensive
items. Your filter caps will also be expensive.
You do *not* want to use a 24 volt DC input to get
12 volts regulated out. At 60 amps, you'll be producing
720 watts of heat, meaning a huge area of heat sinking.
More expense.

If you *really* need 60 amps at 12 volts, using a 12 volt
deep cycle lead acid battery is likely to be cheaper and
easier for you.

In the meantime, you can experiment with much smaller
supplies - say 5 amps max - to learn, if learning
interests you. At lower currents, the learning experience
won't cost as much in blown up parts and burned fingers.

Ed- Hide quoted text -

- Show quoted text -

How can I tell if the transformer is having 100A capacity?
May be my friend bluff me saying that his PSU is giving 60A.

The dimension of the transformer core is as below:



6"
------------------------------------------------------
/ /
2.8" / /|
/ / |
/ / |
/-----------------------------------------------------/ |
| | |
| | |
| <-------------- 4" ------------------> | |
| +--------------------------------------+ | |
| | ^ | | | | |
| | | | | | | |
| | | | | | | |
| 1" | | | | | | |
|<---->| 3" | | | | |
5"| | | | | | | |
| | | | | | | |
| | | | | | | |
| | V | | | | |
| +--------------------------------------+ | |
| | /
| | /
| | /
-----------------------------------------------------|/
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

To measure the second wire size, I'll need to cut open the insulator.
The filtering Caps are 6 pieces of 10,000uF 50V electrolytic.

Alen

Nice diagram. That is not a 100+ amp at 30V (secondary)
transformer - too small. Why 30 volt? Because the rectified
and filtered DC output from a transformer providing 30 volts
AC would be about 42 volts, so I'm guessing the transform
provides 30 v AC.

You *really* need to forget about building a supply that
provides 60 amps output. It is a dangerous and expensive
project, and you need to *know* what you are doing if
you build one. It is *not* the kind of project where you
can get a schematic from the internet and a bunch of
cheap parts, connect them up and have a good result.

Ed

 

[neon]

this is great all these clowns with spice analyzers putting different numbers and so forth. coming out with god knows what. the answer is NO never. And i don't need spice for that. spice is a tool not a designer is just as dumb as the people that wrote it. But don't take my word for it.