Hi all,
I've chosen a project to keep my studies of electronics up, which is designing a
really good LED flash light.
Imagine I have 5V battery with a 55 Ohm resistor giving me 90mA, this is pulsed at ~25 Hz with a 50% duty cycle square wave.
Over time, the battery drops to 4.2 V. Now my current is ~76mA. The data sheet be linked below, has a plot of the forward voltage required for a given current. At 4.2 V, the forward current is only 60mA. Am I understanding this right ???
So what happens to the extra current my circuit is trying to pump through the LED ? Does it create extra heat and thus wear and tear ....?
I'm trying to find a way to practice using a FET as a current source. Does it help to keep the current stead, if the device requires a certain voltage for a given current anyways...if I was operating at 10V and wanted a constant current down to 4.2 V, then a current source clearly makes sense. But operating down in the elbow of the diode's IV curve...I feel kinda lost...
TIA,
wbg
http://www.alldatasheet.com/datasheet-pdf/pdf/103642/MARKTECH/LM1PWH101.html
I've chosen a project to keep my studies of electronics up, which is designing a
really good LED flash light.
Imagine I have 5V battery with a 55 Ohm resistor giving me 90mA, this is pulsed at ~25 Hz with a 50% duty cycle square wave.
Over time, the battery drops to 4.2 V. Now my current is ~76mA. The data sheet be linked below, has a plot of the forward voltage required for a given current. At 4.2 V, the forward current is only 60mA. Am I understanding this right ???
So what happens to the extra current my circuit is trying to pump through the LED ? Does it create extra heat and thus wear and tear ....?
I'm trying to find a way to practice using a FET as a current source. Does it help to keep the current stead, if the device requires a certain voltage for a given current anyways...if I was operating at 10V and wanted a constant current down to 4.2 V, then a current source clearly makes sense. But operating down in the elbow of the diode's IV curve...I feel kinda lost...
TIA,
wbg
http://www.alldatasheet.com/datasheet-pdf/pdf/103642/MARKTECH/LM1PWH101.html
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