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0-30 Vdc Stabilized Power Supply


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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.

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  • 2 weeks later...

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

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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

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  • 2 weeks later...

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?


"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.


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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.

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  • 1 month later...

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.

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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).

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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.

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