Blue Sea 8034 Green LED Indicator Light

I found that these are too dim for my use, so I removed the heat shrink tubing on the leads to see how it works. It consists of an LED in series with a standard diode (to protect the LED from reverse voltage every AC cycle), and a 150K resistor (to limit the current during forward conduction). Simple design, though one diode protecting another in this fashion is always a bit sketchy - if the protection diode has much reverse leakage, the LED will see a large reverse voltage every cycle, which could eventually damage it. A 1M resistor in parallel with the LED would eliminate that possibility but this design doesn't include one. Is this a real problem? I don't know. 150K doesn't allow a lot of current to flow through the LED, but that's probably the smallest value they were able to use while keeping a 1/4W resistor. A smaller value resistor would increase brightness, but would also get hot so a 1/2W or larger resistor would be needed, increasing bulk (and cost, somewhat). Peak current calculates to about 2.3mA, but that's only at the peak of the AC cycle. The average current by my calculation (could be wrong) is only 720 microamps, not even a milliamp. Part of the reason the average current is so low is the LED only conducts during half the AC cycle. It's off during the other half, since the polarity of the AC is reversed. LEDs generally look good in the 10~20mA range, so 720uA is pretty feeble. The persistence of your eyes will increase the apparent brightness some, but still these are very dim. For use in a fluorescent lit shop where 240V is likely to be found, they are almost invisible.

I wish I had found these sooner. I started using some that are a little larger and these are so much nicer. Small and bright they are very nice indicator lights. I use a row of them at the RV door to show what is still on when we leave.