Hi, all
Recently, I have a system running at 62V max, 54V nominal based on voltage divider formula. I wanted to have a little alert LED, so I was thinking about using 10, 1kohm resistors, and adding the LED bewteen the 9th and 10th (or 1st and 2nd, if it matters), to get at most 6V and just a few mA.
Is a better/easier way? Is this a really crappy way? Or is this a perfectly fine way?
Recently, I have a system running at 62V max, 54V nominal based on voltage divider formula. I wanted to have a little alert LED, so I was thinking about using 10, 1kohm resistors, and adding the LED bewteen the 9th and 10th (or 1st and 2nd, if it matters), to get at most 6V and just a few mA.
Is a better/easier way? Is this a really crappy way? Or is this a perfectly fine way?
Why a divider?
LED's are current driven and so all you need is a single resistor scaled to suit the supply.
Modern LED's are bright at 1 milliamp or less so lets use that as an example.
R=V/I so we get 62/0.001 which is 62k. Wattage needs to be W=I squared multiplied R so we get (0.001 * 0.001)*62000 which is 62 milliwatts. We would use a 0.5W though for its higher voltage rating.
LED's are current driven and so all you need is a single resistor scaled to suit the supply.
Modern LED's are bright at 1 milliamp or less so lets use that as an example.
R=V/I so we get 62/0.001 which is 62k. Wattage needs to be W=I squared multiplied R so we get (0.001 * 0.001)*62000 which is 62 milliwatts. We would use a 0.5W though for its higher voltage rating.
I'm not sure on that either.
Don't know if the divider was to run just the LED or whether the divider already runs something else... either way a single resistor and LED has to be the simplest solution and allows brightness to be altered easily if needed.
Don't know if the divider was to run just the LED or whether the divider already runs something else... either way a single resistor and LED has to be the simplest solution and allows brightness to be altered easily if needed.
Ask yourself how much the modulation of any fluctuation in LED current (noise) will affect a raw supply by. A quarter of a half of nothing 😉
Here we are discussing a visual indicator running on supplies of around 60v.
We will have to wait for the OP to enlighten us on the actual requirements.
Here we are discussing a visual indicator running on supplies of around 60v.
We will have to wait for the OP to enlighten us on the actual requirements.
Thanks, folks!
I have a bunch of 1k, 1/4W resistors, so 10 of those will work fine. I guess that 6mA at 60V is only 360mW, which might be a bit high. I could always use a lot more resistors and experiment by reducing it until I get to a suitable brightness.
I have a bunch of 1k, 1/4W resistors, so 10 of those will work fine. I guess that 6mA at 60V is only 360mW, which might be a bit high. I could always use a lot more resistors and experiment by reducing it until I get to a suitable brightness.
If you really must use a series chain of resistors then add the LED in parallel across any one of the chain of 10 and then add further resistors in parallel with the LED to cut the brightness.