From 24-VAC to 9-VDC or 5-VDC

use a full bridge rectifier to convert your AC to DC, then use a linear voltage regulator (LM317, for instance). You can google "dc power supply design" for more info.

Hi and Thanks for your quick reply,

Here is a Link that shows what I'm trying to atchieve ...

Go to: http://ourworld.compuserve.com/homepages/Bill_Bowden/page5.htm

near the middle of the page you will see a Title ( Fading Color LEDs ) with lot of texts, below that there are 2 drawings;

#1 is with LM1458

#2 is with LM324 ( The one that I am working with. )

It work very good with a 9 Volts Battery ( I love this Effect ! ) but I want to be able to use it with a 12 & 24VAC. current.

Everybody want me to use a LM317 with Capacitors, Resistors etc...

I'm very limited in space with my PCB. ( 1.500" x 1.650" )

My question is:

Is there somewhere an IC that would replace the LM317 + all other components that need to be added and that will drop the voltage considerably so I can put 3 LEDs per transistor and still use this LM324.

( There most be something somewhere ! )

Thanks,

Vitalimus

So it is a Free-running multivibrator driving complimentary transistors.

The circuit below illustrates two pairs of LEDs that operate out of phase so as one pair slowly illuminates, the other pair will fade.

With the low current drain on your power supply you can use an LM78M08, 8 Volt, 0.5 Amp, TO202 package, Fixed regulator. No adjustment network. Your Rectifier and Filter Capacitor will be smaller value as you don't need so much filtration for such a small current draw. Your dc input has to be about 15 Volts to work properly.

Hi sir,

Yes this is the one ...

Like I said, with a 9 volts battery, everything is working ver well.

Now what I would like to do is to use a standard 12VAC. and 24 VAC. current from an wall outlet to start this project....

I cannot use a standard power supply ( no space )

Is there a regulator already made that will transfer the AC to DC. without having to add all those components?

Thanks,

Vitalimus

What about a "plug top" supply.

Hi Randall,

No I cannot use this type of power supply.

My application is very special and I need to use the existing current ( 12VAC. )

Imagine that you have 30 Lamps screwed on a Wall and that had already a 12VAC. current in it ... I have to use this current, I don't haveroom or space in the Lamp to include a little power supply, I need to design a PCB. with LEDs and having an effect like the one from the LM324.

thanks,

Vitalimus

The problem is that the 12VAC current you keep referring to is actually 120 Volts Alternating Current. An LED requires between about 1½ and 4 Volts to operate: if you don't "transform" the mains down to the voltage your working at you will just be wasting 120X0.02 = 2½ Watts and you will need to get rid of the heat somehow.

What about those little lights they put in mains distribution extension leads.

I have 12VAC track lighting in my garage so I am assuming you have a similar electrical source to work with.

You need a way to rectify, filter, and reduce the voltage to about 9 volts.

Rectifying and filtering 12 Volts ac gives you an unstable no-load voltage of about 15 volts.

This circuit is a voltage stabilizer that reduces to a lower voltage by dissipating heat from "R".

"+" would be the rectified Voltage fed through "R".

"D" would be a 9 volt Zener that provides 9 Volts stable output.

Swap the positions of "D" and "R" and "D" would drop the input voltage by 9 volts and "R" will be the load of your Blinker circuit. "D" would have to be a Zener value that drops the voltage to the desired value.

If "+" is 15 Volts then the Zener would be 6 Volts to give you 9 Volts out.

That is about as basic as it gets.

While this is easy, this won't work without rectification and filtering. A simple variation of this can produce a stable stepped down voltage once my previous questions are answered.

On that note, I do not need to know values to great precision, approximate starting points will easily do.

Hi Red,

In my recent post I said: "You need a way to rectify, filter, and reduce the voltage to about 9 volts. Rectifying and filtering 12 Volts ac gives you an unstable no-load voltage of about 15 volts."

Did you miss it somehow?

Jon

Hi Jon,

No I did not miss it,

I'm trying to find out something that will be much simpler like an IC CHIP or similar to replace the Rectifier - Capacitors - Diodes - Résistors to rectify the current because my space on my PCB. is limited ( 1.500" x 1.500" )

Thanks,

Vitalimus

Vit,

The "did you miss it" was addressed to Redfred's comment.

No, I did not miss the rectify and filter comment. My point was that the resistor and zener diode you showed was not doing rectification and filtering. Your earlier comment did not state that the resistor and zener will not do the rectification and filtering. My point is to fit all components of an AC to DC power supply circuit inside 2.25 square inches, requires more information than we have. Your space limitation is larger than a design I've already made to convert 24 VDC to 5VDC. In that case I knew all of the questions I'm asking you so I could proceed. To properly size the filter the frequency of the AC should be known. To scale the voltage changing circuitry the initial voltage range must be known. To prevent human or equipment damage, one should know the expected environment. I also have the luxury of surface mount circuit board fabrication and assembly.

I am willing to help those who just require some guidance. My previous post listing all of my concerns were the collection of things that immediately came to my mind of what needs to be known to successfully meet the limitations you've specified. Should you answer some or all of my questions, I'll offer more refined suggestions. That is unless I feel the new information makes this supply implausible. Then I'll explain why I think you're exceeding practical limits.

Ok. You are looking at the whole picture as I should have while including getting the voltage down to 9 volts dc without more loading.

Sounds like you could do his whole project from start to finish using his size limitation and the latest miniaturized technology.

The cel-phone charger in my car is even smaller and without all of the hardware it may fit in yours.

It can run on 12 and 24 volt electrical systems.

Hi Kudukd,

You maybe right but there is my situation,

I cannot use surface mount parts, my eyes are not good for that, I need to use throught holes parts and those parts are bigger than the others.

Vitalimus

Ok, so things can now get much tighter but not impossible. Use http://www.newark.com/multicomp/1w06/bridge-rectifier-1a-600v/dp/15J2227

for your bridge rectifier. It's a through hole part that's smaller than most. Identify how much current your blinking light circuit draws. Easiest method is to just measure with an ammeter the battery driven version you have. This will determine if you must use a switching supply or the simple linear rectifier and what capacitance size for the filter capacitor.

Red,

While I was the preparing the first response in this thread somone slipped one in about changing AC to filtered DC

Take a look at entries 1 and 2.

Jon

Where is your 12 or 24 V AC coming from?

I am thinking he means 120Vac or 240Vac? That would be "standard."

Mains! On a 1½"^² PCB?

But, my worrying gut feeling is that you may be right.

There are many ways this can be done. In all scenarios I can think of, there is no single magic component though that will do what you state and imply. So a circuit design will have to be crafted. But you have to many uncertainties to provide simple answers. Here are a few questions you should answer before proceeding:

• What is your nominal supply voltage? 12VAC, 24VAC 120VAC or 240VAC each voltage produces their own circuit design considerations.
• What is the nominal frequency of the AC power? 60 hertz, 50 hertz, 400 hertz again each frequency produces different considerations.
• Can you fabricate this design using surface mount components? This will permit smaller packaging but likely more sophisticated assembly than you may have.
• Do you have any in-rush current limitations?
• How much power will the supply provide? Your description implied unspecified expansion.
• It appears that you won't need a very tightly controlled output voltage, is this true?
• How much power can the supply dissipate?
• Any unusual environmental considerations? Explosive atmosphere, temperature extremes, humidity, water submersion, etc.

That's at least a good first batch of questions.

Hi Red,

Here are some answers

Nominal voltage is 12VAC - 60Hz.

Yes I can fabricate a PCB.

Explain ( in-rush current limitatrions )

Environmental considerations ( very little humidity ) Room tempered at 60 to 65°F. in winter and 65 to 70°F. in summer.

Hope those answers will help,

Thanks

Sorry, when I flew through the earlier postings I missed your reply answering some of my questions. I don't want to do a complete supply design here (I normally get paid to do that ) but I certainly will help you design one yourself.

Ok, as others here have suggested, go with a full bridge diode package to rectify. This may at first seem like a large part but you can locate surface mount components (the Vishay DF005S thru DF10S series will do well, Newark has a few DF08S available). This doubles your filter frequency, so the filter capacitor can be smaller. The current drawn off of this capacitor every 1/(120HZ) will determine how much ripple gets produced and therefore what value capacitor will be used. (More on this later.)

Now, the first time this capacitor gets charged is the in rush current. Depending on the peak current your source can or cannot tolerate, you might add a small ohmic value resistor between the diode bridge and capacitor to limit the in rush current.

Now the peak voltage of a sine wave is Vp=√(2)*Vrms so 12VAC produces a peak voltage of about 17 volts. So the peak voltage on the capacitor will be 16.4 volts when you include the diode drop. Since you are looking for a 5VDC output, your ripple on the filter capacitor can be quite safely 10 volts peak to peak.

Knowing this you can now choose between circuit types and topologies. A linear regulator circuit like the previous resistor and zener circuit or just a simple all in one linear regulator like the 78LS05 linear regulator so many companies manufacture will produce a very clean, voltage at the cost of a loss in efficiency. For in your case a linear regulator will be dissipating twice as much power as your entire regulated circuit. If your regulated circuit will only draw 0.1W this won't be a problem. But you can see that this can become a problem. More complicated switching regulation like the LM2594M-5.0 will require a few more parts (they'll fit inside your foot print) but will work more efficiently and thus not dissipate much additional heat load.

Well there you go, that's my approach for you.

Vitalimus,

My tiny cel-phone charger can convert 100 to 240 Vac 50 - 60 Hz to 5 Volts 0.7 ma.

It is about the size of a "D" cell.

Jon