14-11-2012, 09:47 AM
I saw that on the data-sheet, Mark, but thanks for the reminder.
I've always been a bit puzzled by the 240Ω resistor as when reading about them the words "usually" or "typically" tend to go with it. It's also odd that it's an E24 value which gives the idea that it's important.
There's a calculator and a table of values here and, as can be seen, they are all over the place.
I know I'm an arch "Amateur Twiddler" but have only blown one LM317 up. That was when testing a magic eye and I accidentally touched the HT and found that "They don't like it up 'em." The odd thing was that I'd instinctively been reaching for a blocking capacitor before realising that I wanted DC to get through; it was only after the event that using a diode occurred to me.
Those panel meters do look worthy of investigation, David, though if you could blow one I'm not very confident that it would survive my tender ministrations. I can see myself building a bigger box.
I never expected fitting an LED to be so involved but I'm not knocking it as it's all good fun and this thread has gone down some very interesting side-roads on the way.
- Joe
I've always been a bit puzzled by the 240Ω resistor as when reading about them the words "usually" or "typically" tend to go with it. It's also odd that it's an E24 value which gives the idea that it's important.
There's a calculator and a table of values here and, as can be seen, they are all over the place.
I know I'm an arch "Amateur Twiddler" but have only blown one LM317 up. That was when testing a magic eye and I accidentally touched the HT and found that "They don't like it up 'em." The odd thing was that I'd instinctively been reaching for a blocking capacitor before realising that I wanted DC to get through; it was only after the event that using a diode occurred to me.
Those panel meters do look worthy of investigation, David, though if you could blow one I'm not very confident that it would survive my tender ministrations. I can see myself building a bigger box.
I never expected fitting an LED to be so involved but I'm not knocking it as it's all good fun and this thread has gone down some very interesting side-roads on the way.
- Joe
