Sallala

0-30 Vdc Stabilized Power Supply

Recommended Posts

In reply to the question asked by Derfly, you can connect the potentiometers in series. More importantly, for the fine adjustment, you will want to use a 10 turn or a 15 turn or even possibly a 20 turn pot to give you the accuracy you want to achieve. This should be on the smaller value pot as you want maximum number of turns for smallest voltage change.
Hope that helps a little.
MP

Share this post


Link to post
Share on other sites

MP Thanks,

I undestand wiring in series but the variable resistors in this project have three connections. To wire two variable reistors in series, how is this done. Could you possible supply a diagram?

Many thanks,

DerFly

Share this post


Link to post
Share on other sites
Guest KIRKCHABO

Help!
I am new to the electronic world and i need some clarification on the
resistors in this project.

R1=2.2Kohm 1 watt (ok)
R3=220ohm 1/4watt (ok)
R4=4,7Kohm 1/4 watt (?)
R7=0,47Ohm 1/4 watt (?)
R9=2,2Kohm 1/4 watt (?)
R14=1,5Kohm 1/4 watt (?)

I kown this probibly sounds dumb but I don't get this?


Thanks In advance


Share this post


Link to post
Share on other sites
Guest KIRKCHABO

thanks mp

help I checked all solder joints and componets but when i start it up
it seems ok till i put a load or even without a load (meter) when i turn up the current dial even a little bit the led starts flashing and i go into overload.

lost in space

Share this post


Link to post
Share on other sites

All the components around the IC are for the current limiting circuit. You should check all of these parts for correct values and orientation.
Did you leave anything out that you felt was not needed? Even the LED is part of the current limiting circuitry.

MP

Share this post


Link to post
Share on other sites

I have a heat sink from an old stereo receiver that I think is substantial enough for this project. The project page states:

"...use the mica insulator between the transistor body and the heatsink..."

I will be able to re-use the screws and plastic hole inserts but there was a piece of clear plastic between the sink and transistor that is too small. What should I use? Is there something around the house or hardware store I can use or do I have to hope :-\ my local electonics store guys will know what I am talking about?

Also:

"Use a little amount of Heat Transfer Compound between the transistor and the heatsink..."

Would that be between the transistor and mica insulator, between the mica insulator and sink, or a layer on each side of the mica insulator?

(Curiously, the old, built-like-a-tank receiver didn't use any goo; just the piece of clear plastic between the sink and transistor.)

On another note, I received the 2N3055A and numerous other "samples" from ON Semi http://www.onsemi.com They charge $15 US for shipping and handling but I felt it is well worth it if you order enough pieces or you are having trouble finding stuff locally.

Thanks.

Share this post


Link to post
Share on other sites

Hello FireFly

You can buy a plastic insulator that is made exactly for the dimentions of TO-3 package transistor and has good heat transfer characteristics. The clear plastic you have is old type. You can also find other kind of matterials that are like rubber . Almost all electronics parts stores has it.

I attach you also an image that saws how to use it.



Regarding the "Heat Transfer Compound" you can put it both sides of the mica isulator for better performance.

Share this post


Link to post
Share on other sites

Hi,

I want to use the pcb of the 30V power supply but when i print it, it Becomes too much big, Can anybody tell me how i can fit it in actual size (12.5cm x 8.7cm)

your help is appreciated in advance


Share this post


Link to post
Share on other sites

The best way to print it out correctly is to make some test prints to find the correct ratio. Take a part with fixed dimensions (like an IC) and try to fit it on the print out paper. Then change accordingly the ratio (resize scale) to achieve the correct dimensions. It is better to use a program that allows you to change the percentage (%) of the print out.

Share this post


Link to post
Share on other sites

This power supply looks a little simple. I would design my own and forget about the opamp, most likely. With so many possibilities, you have to wonder what the ideal operation is. This is the circuit I use presently, but I need a better one.

Share this post


Link to post
Share on other sites

Do not use a 2N2222 instead of a 2N2219 for Q2 since it must dissipate up to 5W and therefore is shown with a heatsink.
The 2N2219 has a larger metal case and is designed for use with a heatsink. The 2N2222 has a small plastic case and cannot dissipate more than about 1/3W. With 5W in a 2N2222 it will smoke then burn.
Although the two transistors have the same voltage and current ratings, the little 2N2222 is designed to SWITCH current (when switched-on it has very little voltage across it and therefore low power).

Share this post


Link to post
Share on other sites

Hello Tom and others,
You CANNOT put stabilized power supplies in parallel since you cannot ensure that they have EXACTLY the same output voltage. The supply with the slightly higher voltage will carry the whole load while the lower voltage one(s) will tell its regulator that the voltage is high enough or is too high and therefore to shut-down.

Although you CAN isolate parallelled supplies with a series resistor from each one's output to the load, so that the supply with the slightly higher voltage carries enough current to allow its voltage at the output of its series resistor to drop to the level of the slightly lower voltage one(s) so that this one (these ones) carry the remaining current. But those series resistors ruin the voltage stabilization since the output voltage will fluctuate with load current changes.

Share this post


Link to post
Share on other sites

audioguru, what are you referring to in this post? Multiple regulators in parallel? Complete supplies in parallel? Which post are you replying to?

MP

Share this post


Link to post
Share on other sites

MP, I was replying to Tom in his reply #9 in this post where he asked if he could parallel 2 of these Stabilized Power Supplies to get more output current.
My reply refers to paralleling these supplies, any other regulated supplies and IC regulators in general.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now