Converting AC to DC

[tmichutka]

Hi all!

I'm fairly new here but absolutely love it.  This is the only forum I visit regularly.  So here's my question, I've converted my EH Deluxe Electric Mistress to true bypass, took out the internal transfomer and used a wall wart, now I'd like to hook up an LED.  Only problem is that it uses 16VAC for power, so I need to convert it to DC to use an LED.  I know it requires rectifier diodes but that's the extent of my knowledge.  I have various rectifier diodes laying around (I know I have a bunch of 1N4001s).  Also I'll mention this, I'm thinking of putting a GGG MXR Phase 45 clone inside for fun, since I don't currently own a Phaser, so converting it to 9VDC would be a plus, but I can figure that out later.  Right now my main concern is converting AC to DC.

Thanks much!!

[theehman]

The AC is converted to DC on the circuit board, about 12-15vdc I think.  You can just tap off the DC line anywhere with the proper value resistor for your LED.  Find pin 8 on an op-amp and trace it back to the power supply.

[Pushtone]

Rectifiers convert AC to DC.
Your also going to want to include some filtering too.

Look at the GGG regulated power supplies and take the section AFTER the transformer.
You already have that part in the wall wart your using.

Does your wall wart have enough current to drive the extra circuit and LED?

The EM must be rectifing and regulating the AC because of course it needs DC power to work.
Is there a spot where you can tap into the +9 or 12VDC?

FWIW: I think you can run an LED off of AC current. I've seen schematic on the net for that.

[tmichutka]

Awesome, thanks guys!  I'm going to start looking for the DC on the board right now!  I'll follow up with specifics in case this helps anyone else looking to do the same.

I've said it once and I'll say it again, this forum ROCKS!

[R.G.]

Save yourself a whole lot of time and go read everything at GEO - http://www.geofex.com .

Amongst a whole lot of other things, there is an article there on power supplies, and how AC is made DC. The answer to the question you haven't thought to ask yet is probably there.

[dxm1]

Can't you run the LED from 16VAC?  If the reverse voltage of the LED is too low, why not a rectifier diode in parallel (reversed)? And the appropriate current limiting resistor, of course.

[Fender56]

Can't you run the LED from 16VAC? 

Certainly, but the intensity will be reduced since it will blink at a rate of 60 Hz. Worth a try since it is an easy solution!

[Mark F]

Save yourself a whole lot of time and go read everything at GEO - http://www.geofex.com .

Amongst a whole lot of other things, there is an article there on power supplies, and how AC is made DC. The answer to the question you haven't thought to ask yet is probably there.

+1! I think more people ,especially newb's , should do this.

[dxm1]

Certainly, but the intensity will be reduced since it will blink at a rate of 60 Hz. Worth a try since it is an easy solution!

If you use the reverse voltage protection diode, it should blink at 30Hz. Still, this is about the normal video frame rate, so it should not be noticable. You may have to increase the current (keeping in mind the 50 percent duty cycle) to get it bright enough.

Still, we're only talking three parts here...

[tmichutka]

I figured this out.  The first response was right, the AC is converted to DC on the board and I tapped a point with 12VDC which worked like a charm.  I was always under the impression that you have to use DC for LEDs.

As for GEOFEX.COM, I'm very familiar with that site but I hadn't seen his article on power supplies and converting AC to DC.  I'm glad you metnioned that because I am still interested in learning how specifically to convert AC to DC (it can't be as simple as just putting a rectifier diode in series can it?  Nothing ever seems to be that simple, but then again I am a newb ).

Thanks for all the responses!  They were all very helpful and informative.

[R.G.]

It ...can... be as simple as putting a rectifier in series. That method produce very crude pulsing DC with a lot of ugly ripple. There are better ways.

[bkanber]

(it can't be as simple as just putting a rectifier diode in series can it?  Nothing ever seems to be that simple, but then again I am a newb ).

It ...can... be as simple as putting a rectifier in series. That method produce very crude pulsing DC with a lot of ugly ripple. There are better ways.

It can be _even_ simpler.. just one diode in series. Half wave rectification is still considered DC Though, you'd obviously never use half rectified DC (or even full rectified DC without filtering) for a DC circuit.

In short, the most common way to convert AC to DC is to transform the AC power down, then full wave rectify (that just takes the negative part of AC and makes it positive), then filter using a capacitor (that kinda smooths it out and can be acceptable for many applications) and then use a voltage regulator IC (that makes the DC very smooth, and acceptable for just about every high performance DC circuit).

So, there's AC->DC in one sentence, just so you know for future reference.

I'm glad you like our forum, tmichutka! Stick around!