new LED bulbs marked DC for AC?

I'd just stick a diode in series with the power input, problem solved and no doubts about the power source.

Thanks John.

I was wondering if I should have put a whole bridge rectifier inline?

The bridge will balance any DC offset generated by the current to the bulbs, so if that's important, the bridge will be a better choice.

I believe the bulb already has a bridge rectifier inside it.  With a symmetrical bi-pin connector, what stops you from plugging it in "backwards"?  In other words it allows either orientation which means bridge rectifier.  I believe there are 2 diodes on each side of the internal board as circled below.

Let's see.  They say 1.5 Watts, 12V DC.  That's 1/8 Amp.  Presumably there are 4 of those 22 ohm resistors, so if each resistor limits the current going into two paralleled sections of 3 LEDs (like on the 12V LED strips) the math works out when accounting for the voltage drop into 2 diodes (only half of the 4-diode bridge is active with DC).

Why would they stamp it so prominently with DC?

Easy to find out if it has a bridge, just connect it to DC, then reverse the polarity.  If it lights both ways, it has the bridge.

Again, it has that bi-pin connector so nothing prevents you from plugging it in either way.  It is marked DC because 99.9% of applications are 12V DC. 

Consumers are lazy.  If the average consumer saw a bulb labeled 12V AC/DC (vs. 12V DC) I'll bet a good percentage would think you need to supply it AC, some weird combination of AC/DC, or whatever...and not buy it.  In my opinion that is.

I have a different version in my hands that I got at Walmart. I tried it and you can reverse the DC and it still lights.

The Walmart version has 6 sides of 5 LEDs and 3 more on top. It has a white plastic ribbed base. It is very bright. It got warm running outside on AC during a test. It did work. The package does not state AC or DC? It says it's made for landscape lighting and cabinet lighting.

 I went on to Walmart.com looking for more and I could not find them. I found more on ebay with less LEDs inside.

I have used these on ac for the past 3 years with no problems. I got tired of replacing the 12 volt filament bulbs which can be costly. Also the load on the transformer is reduced by quite a bit.Also these bulbs come in a standard scew base so you can use a regular 117 volt fixture but run it on 12 volts. I did this with 2 outside lanterns just recently. If you have any more questions just ask.

stan2004 posted:

Again, it has that bi-pin connector so nothing prevents you from plugging it in either way.  It is marked DC because 99.9% of applications are 12V DC. 

Consumers are lazy.  If the average consumer saw a bulb labeled 12V AC/DC (vs. 12V DC) I'll bet a good percentage would think you need to supply it AC, some weird combination of AC/DC, or whatever...and not buy it.  In my opinion that is.

Stan

Not disagreeing with you, but it would make more sense to just label it 12V, as the average consumer does not understand the difference between AC and DC. 

 I switched over to LEDs on most of my lights just awhile back too. I also got tired of changing bulbs. Now those lights are just at the end of their span. The wires have corroded enough that they're not reliable. The stab in type connectors just don't seem to last for years. So I'm rewiring and tackling some extra lights that never got upgraded to LEDs.

 On some of these extra fixtures, my normal go to LEDs just aren't bright enough. So I went searching for options. I bought a few MR11 bulbs that looked great. When I went back, I couldn't find the exact ones any more. So I came across these new types while searching for bulbs that would work in some sockets that I already ordered.

 I wanted to throw in a guess that labeling these bulbs "DC", may make them attractive for automotive use too? I imagine that's a bigger market?

The bulbs arrived today. I gave them a quick test and they light with AC or DC power. They're almost a pure white, not real warm or bluish. They look very good to me for what I need. I bet they could do a lot of jobs on layouts.

I can't win anymore! It's not for trying though.

I bought the bulb holders thinking it would make my life easier. The attached wires won't accept any solder? So I went to my bench and tried again. I've got extra paste dripping and still it won't accept solder???  Urrrrgggg!

Maybe I will crimp the wires or solder directly to the sockets???

Joe, you have to strip the insulation off first.

Sorry, couldn't resist!

John, I knew you would!!

Well the solution was too simple. I bent the leads coming off the bulbs outwards from center about 10 degrees. I was afraid to do that. I did it anyways.

I jammed the bulb leads behind the original socket tabs..... and we'll see how long that lasts. It was too easy.