Needing circuit to run LED off 8 VAC

[fredcohiba]

Hello,

Looking to see if anyone has a schematic for running an LED bulb off an 8 VAC line meant to power an incandescent bulb (backlighting for a set of power meters on a Kenwood KA-5700). Thanks.

 

[ConradH]

Use two in parallel in opposite directions so they alternately light and protect the other one from reverse voltage. Use whatever resistor suits your need for brightness and keeps them below the maximum current. I like the CREE surface mount ones as they'll fit just about anywhere.

 

[sKiZo]

I'm running 12v lamps in my Sansui ... off 8vac. They're super bright "warm" lamps made for automotive use. No problems with the voltage mismatch after a couple years.

May seem bright in this pic, but that's without the smoked dial glass installed. Those LED fixtures replace the almost unobtainable globe lamps that Sansui used in this receiver. I did eventually cut back the collars on the mounting rubbers for the meter lamps ... Bottom left, you can see one cut and one not.

You can see here that the bayonet bases pop right off ...

What's nice is the super brights at the lower voltage emulate the output of the original incandescent lamps quite nicely ... having multiple LEDs in each fixture also help tone down the hot spots I never liked about LED lighting. Yes, you still get bright spots, but those are similar to what I had with the stock lamps. Compare the green tuning meters with the white power meters. The power meters are the original incandescents ... a real PITA to get out as they tend to weld themselves to the meters over time. Those were all good so I left them alone for now.

 

[fredcohiba]

sKIZo - you're a genius! Thanks for your post. I tried your method this AM and it works and looks fantastic. I had some bulbs left over from an upgrade I made to the license plate lights on my car.
The amp meter lights are just the right brightness. Thanks again.

 

[sKiZo]

Yes ... I am a legend in my own mind. <G>

Glad it worked for you. You MAY (or may not) notice some flickering every now and then depending on the amount of ambient light in the room. Some folk are more sensitive to it than others. A simple dandy solution for that is the addition of a rectifier to the circuit that converts the AC supply to DC. Found this handy dandy bit of tech on that auction site ...

Search for "led rectifier" and it pops right up. What was real handy for me was as mentioned, half my lights are LED, the other half the original incandescent bulbs. Whether they get AC or DC depends on which side of the rectifier I draw the power from. If I ever "upgrade" the rest of the incandescents, simply switch the feed lines for those bulbs to the other side.

Pretty compact too ...