Sunday, 26 May 2013

Steampunk Electronics–LED Goggles Part II

The circuit for this project is pretty straight forward. Basically, each of the LED connect to the positive through the anode and to the negative via a 150 ohm resistor.

On a breadboard, it looks like this.


There is a jumper going from the positive to each LED anode. The cathode is connected to the negative through the resistor.

When it is powered up, it looks like this.


There are 20 LED in parallel.

This is enough LED for two eye pieces, making up a pair of goggles. I need to work out how long it takes before the LED drain the 9 volt battery. To do this, I’ve simply charged the 9 volt battery and marked the time when the LED were connected.

I did a rough test last night, but with 100 ohm resistors instead of 150 ohm. I started to get no light from some of the LED after 3 hours. That’s not a bad outcome. So long as I use rechargeable batteries, it shouldn’t be a problem.

I don’t know if the increase in resistance will make that much difference in the power consumption … but I guess that it will increase the glow time by about 33 – 50%. The power went on at 7:14pm today.

I don’t have any data on the LED power consumption.

Next image is at 8:30pm


Definitely less bright after 1 hour 15 minutes of operation.

9:30 and some of the LED are dark and overall, much less light output from the array.


I kept the LED array powered all night and there was still a very faint glow in the LED after almost 12 hours. Not enough light for anything practical and almost invisible … but still going. I would say that the acceptable level of light was after 1 hour 30 minutes of continuous running. So, this means that either I decrease the number of LED in the array or increase the number of batteries (2 x 9v for instance). The most practical approach would be reduce the number of LED to, say 6 LED per “lens” rather than 10. That works for me. So now the next task is to design and build the PCB for the lens.

That’s not going to happen very quickly at the moment, as we are moving house in 3 weeks and I have a shitload of stuff to pack.

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