TheRadioBoard

This is how I did it and it gives me a noiseless, below the noise level of my scope at least, power supply for my 80m regen.



Nothing new here as far as I can see, but my little trick is to make sure the minimum output current of the LM317 is above the recommended 5mA, This gives me also a decent current through the zener diodes, enough to regulate the voltage to the detector properly.
This circuit can be modified to give a regulated voltage to almost any homebrewed radio I believe. There are calculators for the LM317 all over the place. Just bear in mind that you need at least 5mA for the regulator when you do the calculations, and that you also need to include the currents for circuits that are connected to one or several of the zener diodes. Also make sure that the zeners and resistors can handle the wattage. The zeners can be anything you need or want really.
I used a TO220 packaged LM317, because that's what i had at hand, but I can't see any reason not to use those in smaller packages.

Rune,
I like the LM317 and use it in many circuits. However, it is rated for 40 V max between input and output. In the unlikely event that the output is accidentally shorted for a moment, the 47 uF cap will be "dumped" through the regulator.

National now has an HV version rated for higher voltage. Or an external pass transistor could be used.

In any case I like your idea and use LM317 for a regulator on 1.5 and 2.0V filament supply circuits.

Rich

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Homebrew Radio ex-Silicon Valley

Yes, there are downsides of using an ordinary 317 in this way. I should probably have put a diode across the 317.I think I will have to correct the schematic. And, of course if one or several of the zener diodes short cuts, arrange funeral for the regulator. The advantage is the possibility for several voltage tappings


But no one stock them, or they are too expensive. That's the problem in my part of the world.[/quote]

The TO-220 version of LM317HV is less than 1 Euro, but I don't know who might carry this in Norway.

http://avnetexpress.avnet.com/store/em/ ... &langId=-1

Here in the US, we have distributors who will deal with small customers, such as DigiKey or Mouser, but in Europe??

Rich

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Homebrew Radio ex-Silicon Valley

Good Job rune!

Another way would be just to use "Brute Force" filtering.(large filter caps and chokes or resistors)

I have been led to believe that "voltage regulation" does a better job of filtering a power supply , than would actual filtering. I dont know how true that is though, or if it holds true only for certain regulators( 3 terminal chip vs discrete device regulators).

good work anyways!

73
kb0lxy

In fact, there isn't too many of those here unfortunately.
ELFA will charge me 30 USD tax included, for just one piece.
RS (Radio Supply [England]) will charge about the same for a pack of five.

You Americans are actually very lucky to have cheap access to all kinds of things. It's not like that for the rest of the world, for some reason. It's like they do everything they can to keep certain things unreachable, especially things that can be used for tinkering. I can order things from DigiKey or Mouser, but they will charge me wast amounts of money for shipping, etc.

Is there really a better method for ripple reduction than using linear regulators?
A LM317 will offer approx 70db of reduction, and even a simple circuit with a zener and one transistor will give you a great deal of reduction too.
Here is an example (you'll need Java and some patience. it might not start immediately):

http://tinyurl.com/3ty829h

We seem to accept this benefit without thinking, as we have always had good access to components. I am especially fortunate, as I have shop called HSC Electronics about 20 km south of here. I can buy an LM317 or IRF740 without shipping or order costs. (I do have to pay for my petrol, but for me it can be part of another journey.) HSC also stocks "surplus" goods that they buy from equipment manufacturers, so sometimes I can buy small electrolytics, for example, for 3 or 5 US cents.

Radio Shack (or as I call them "Cell Phone Shack") has a few components and prices are a bit higher, but we have 6 stores in town. Not like the old days when RS catered to experimenters and hams.

Rich

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Homebrew Radio ex-Silicon Valley

I guess not. 70dB is pretty darn good!



Thank You

73
kb0lxy - Eric

Those TO-220 LM317 aren`t that expensive in europe.

I always buy from the bay,...

Item 380352979248
one for 3usd, and 4 usd shipment to europe, makes 7 for one LM317.

"quote"
Any Quantity Shipped Anywhere Within the USA for $3.40
Any Quantity Shipped Anywhere Outside the USA for $4.00
Combine Shipping with other Press-Send Products
"end quote"

Frank

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www.pa2mrx.nl

The cost of an LM317T is 15 cent! That's what I pay. In Europe they are 30 cent if you shop around.