I want to run a 7 segment common anode display by Kingbright (Link to datasheet) . The forward voltage is 3.7 per segment (1.85 per LED) at 30ma Forward Current.
I will be using some 2n2907 PNP transistors (Datasheet) to give power to it from a 5 volt source.
How do I figure the base current of the 2N2907?
It looks like I need 47 ohm resistors for each segment.
However; I can't seem to find a good calculator for the BASE current calculation and it appears as though there are 2 LEDs in series on each segment, so I'm a bit lost. We're working on a temperature display for a smoker in case you're wondering using a PIC microcontroller.
rage
I will be using some 2n2907 PNP transistors (Datasheet) to give power to it from a 5 volt source.
How do I figure the base current of the 2N2907?
It looks like I need 47 ohm resistors for each segment.
However; I can't seem to find a good calculator for the BASE current calculation and it appears as though there are 2 LEDs in series on each segment, so I'm a bit lost. We're working on a temperature display for a smoker in case you're wondering using a PIC microcontroller.
rage
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