LED Light Bulbs: Part 2

Here’s a second part to my previous post.  It occurred to me today that a good way to compare the heat generated by each bulb would be to put the bulb in a container and monitor the temperature over time.  The container will slow how quickly heat escapes and raise the temperature more quickly than if the bulb were open in a room.  I moved the light bulb base and attached the temperature probe to it.

The container I found was a couple of plastic buckets.  Crude but effective.  The buckets were placed over the bulb with the light off.  The bulb was turned on and temperature readings taken at set intervals.  The setup was then allowed to cool for 10 minutes and the test repeated on the other bulbs.

Here’s the results of the test.  I’ve scaled the Y axis to show the LED and CFL data well which cuts off the 100W incandescent bulb data.  The 100W bulb resulted in a max temperature of 165 degrees F after 720 seconds.  The LED resulted in a quicker temperature increase compared to the CFL but settled into a small smaller rate of increase.  At some point all of the temperatures would settle but I didn’t run the test long enough to reach this point.   According to the trends, the CFL would settle at a higher temperature than the LED.  This makes sense because the CFL’s wattage is higher than the LED’s.  How big would the difference between the CFL and LED be?  I’m not sure.  If I had to guess though I’d say the CFL would have a temperature difference around 50% to 75% higher than the LED’s temperature difference.  Both clearly produce much less heat than the 40W incandescent they’re supposed to be equivalent to.

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2 Responses to LED Light Bulbs: Part 2

  1. Nathan says:

    In theory, the slope of that curve should correspond to power draw. Ideally, you’d need an adiabatic system, but an insulated bucket of known volume would be a good choice. It’d be even better if you could seal it. Then the power draw is the slope of that line divided by the constant volume specific heat of (presumably wet) air insidemutilated by the mass of the air inside. It’d be interesting to are how that matched with the kill-a-watt, too. And it’s a good excuse to buy/build a hygrometer.


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