10 VAC to 3 VDC Circuit

[Divetekno]

Hi. Can anyone out there help me by providing a circuit schematic for converting 10 VAC to 3 VDC? It needs very little current at the 3 VDC side, maybe 10ma at most. Any help would be great -thank you.

 

[Birdman Adam]

Off the top of my head I would:

-Use a diode to turn the AC to pulsed DC.

-A capacitor to smooth that out to mostly clean DC.

-Then a regulator, maybe a 7803 (will be 3.3V).
*I would also place the recommended caps before and after the regulator.

This is just my simple idea, I'm sure others have much better ones.

 

[Divetekno]

Thanks for the reply. Any idea of the exact values of the caps to filter the signal? Also, any schematic would be great - I can't seem to find any specific values for these components on the internet.

 

[MikeMl]

Thanks for the reply. Any idea of the exact values of the caps to filter the signal? Also, any schematic would be great - I can't seem to find any specific values for these components on the internet.

Here is how I would do it. I'm assuming that one end of your 10Vac source can be common to the minus side of your load. I'm also assuming that it is 10Vrms, or about 28Vp-p. If not, write back and I can adjust the schematic. You can diddle R3 from zero to ~ 100K, which will adjust the output voltage from 2.5V to ~5V.

 

[Hero999]

How much current do you need?

That circuit is fine for low currents, under 20mA or so but not for high currents.

Also note that the load shown on the schematic, is a 10mA constant current load, not a 10mΩ resistor.

 

[bychon]

Post #1 says, "maybe 10ma at most".

 

[Divetekno]

Thanks mike and others...that circuit should work fine. I am trying to connect 4 (four) small flickering type LED candles to a landscape light transformer. There are other lights on the landscape transformer, so the voltage at my attachment point is only 10 VAC. The four LED candles were originally made to run on a CR2032 3V battery each. Should I connect the LED candles in parallel to the above circuit?

 

[MikeMl]

Thanks mike and others...that circuit should work fine. I am trying to connect 4 (four) small flickering type LED candles to a landscape light transformer. There are other lights on the landscape transformer, so the voltage at my attachment point is only 10 VAC. The four LED candles were originally made to run on a CR2032 3V battery each. Should I connect the LED candles in parallel to the above circuit?

Hook your load where it says "Your Load" in the schematic. The component I1 is just what I used to load the circuit for the simulation.

Where you using a Multimeter for reading the 10Vac? If so, most meters read effective AC (called root mean square, or RMS), so the 28V peak-to-peak I used in the simulation is equivalent to the 10Vrms you would read with your multimeter.

 

[Divetekno]

Mike, yes I used a digital multimeter to read the 10 VAC at the supply point where I want to tap onto the power source.