20-07-2011, 07:41 PM
Thanks for reading my posting and for the comments guys.
Yes, perhaps 3.3V and 20mA were not the best choice of parameters for a worked example - I didn't mean to infer that they were typical. Most ordinary LEDs will be 2 - 2.2V, but ultra bright ones will generally be 3.3V. Obviously it's best if the actual parameters are known for the particular LED, but most of the ones I use are from 'lucky bags' with unknown specs, so I make a few assumptions and if the LED doesn't glow brightly enough, I try a lower value series resistor.
There are now so many varieties of LED - some flash, others will change colour from green to amber to red, depending on voltage, and there are super wide-angled ultra bright pure white ones, which would probably be useful for illuminating dials in place of hard to find bulbs, though they might need a thin coat of amber paint to make them look 'warmer'. I thought I might need to go down that route when I recently restored a Stella 105U as it needed a 19v dial bulb, which I assumed wouldn't be obtainable, but no - they're in plentiful supply!
David
Yes, perhaps 3.3V and 20mA were not the best choice of parameters for a worked example - I didn't mean to infer that they were typical. Most ordinary LEDs will be 2 - 2.2V, but ultra bright ones will generally be 3.3V. Obviously it's best if the actual parameters are known for the particular LED, but most of the ones I use are from 'lucky bags' with unknown specs, so I make a few assumptions and if the LED doesn't glow brightly enough, I try a lower value series resistor.
There are now so many varieties of LED - some flash, others will change colour from green to amber to red, depending on voltage, and there are super wide-angled ultra bright pure white ones, which would probably be useful for illuminating dials in place of hard to find bulbs, though they might need a thin coat of amber paint to make them look 'warmer'. I thought I might need to go down that route when I recently restored a Stella 105U as it needed a 19v dial bulb, which I assumed wouldn't be obtainable, but no - they're in plentiful supply!
David
