Hi Folks, hoping some one can help me out here and tell me if my circuit is correct.
The objective is to drive an IR LED at 38Khz off a 12F683 PIC. This will eventually be used in a infrared breakbeam circuit. I'm aiming at achieving a range of about 10m so I need the IR LED to be flashed as efficiently as possible. I'm just not sure if my circuit is the best way and if my component values are correct.
I'm also not sure if the 2N2222 transistor is the best to use for this application? I've attached my circuit and the two datasheets for you to look at but I'm pretty sure some of you will know the answers before looking at them.
Output voltage of PIC is 4.02V
Infrared LED requires 130mA (I will use up to 125mA)
2N2222 hFE or Beta is 75?
My calculations are;
R2 = 5V/125mA = 40. 39 Ohms resistor to be used.
R1 = 4.02V-0.7V =3.32V.
Beta for 2N2222 is 75.
125mA/75=1.66mA.
(So base of tansistor needs 2mA to switch on properly)
3.32V/0.002mA = 2010 Ohms. (Use 2K resistor)
I'd really appreciate somebodies comments and help on this one.
Thanks a lot - John
The objective is to drive an IR LED at 38Khz off a 12F683 PIC. This will eventually be used in a infrared breakbeam circuit. I'm aiming at achieving a range of about 10m so I need the IR LED to be flashed as efficiently as possible. I'm just not sure if my circuit is the best way and if my component values are correct.
I'm also not sure if the 2N2222 transistor is the best to use for this application? I've attached my circuit and the two datasheets for you to look at but I'm pretty sure some of you will know the answers before looking at them.
Output voltage of PIC is 4.02V
Infrared LED requires 130mA (I will use up to 125mA)
2N2222 hFE or Beta is 75?
My calculations are;
R2 = 5V/125mA = 40. 39 Ohms resistor to be used.
R1 = 4.02V-0.7V =3.32V.
Beta for 2N2222 is 75.
125mA/75=1.66mA.
(So base of tansistor needs 2mA to switch on properly)
3.32V/0.002mA = 2010 Ohms. (Use 2K resistor)
I'd really appreciate somebodies comments and help on this one.
Thanks a lot - John
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