I've searched quite a bit for a circuit that might do this without success so I'm hoping someone is willing to guide me in the right direction with this.
I've bought some high power LEDs, rated at 12v, 1amp with 700 lumens rated output.
I've tested them and found as follows:
They have no internal resistor and will draw infinite current;
They will turn on at approx 7vdc and with as little as 1mA they begin to light;
They provide good brightness from 10mA upwards to 750mA so I expect to drive the LEDs between 10mA and approximately 750mA.
The light output near or above 1A is dangerously bright and may need to be limited if I don't go for a diffuser.
I expect to use 4 LEDs in parallel - 4 x 750mA = 3A = half of a TIP41A rating. The TIP41A NPN transistor is rated for a continuous collector current of 6A so I've bought some of these too.
Supply voltage will be approx 13vdc - 14vdc.
Here's what I'm trying to do:
Step 1> I'd like to create a small driver circuit using a TIP41A. I was thinking of limiting the base current with a 10R in series with a 100R pot.
Q1: What else should I include in this part of the circuit apart from the TIP41A and the base resistors?
Step 2> I'd like to switch this driver with a MOSFET for flashing (approx 5Hz max, low duty cycle). I was thinking of switching the base of the TIP41A using a BS170 together with a pull-down resistor to do this.
Q2: Will this work?
Any other thoughts?
I have a good knowledge of components but only a very limited knowledge of circuit design.
Thanks in advance for any assistance.
I've bought some high power LEDs, rated at 12v, 1amp with 700 lumens rated output.
I've tested them and found as follows:
They have no internal resistor and will draw infinite current;
They will turn on at approx 7vdc and with as little as 1mA they begin to light;
They provide good brightness from 10mA upwards to 750mA so I expect to drive the LEDs between 10mA and approximately 750mA.
The light output near or above 1A is dangerously bright and may need to be limited if I don't go for a diffuser.
I expect to use 4 LEDs in parallel - 4 x 750mA = 3A = half of a TIP41A rating. The TIP41A NPN transistor is rated for a continuous collector current of 6A so I've bought some of these too.
Supply voltage will be approx 13vdc - 14vdc.
Here's what I'm trying to do:
Step 1> I'd like to create a small driver circuit using a TIP41A. I was thinking of limiting the base current with a 10R in series with a 100R pot.
Q1: What else should I include in this part of the circuit apart from the TIP41A and the base resistors?
Step 2> I'd like to switch this driver with a MOSFET for flashing (approx 5Hz max, low duty cycle). I was thinking of switching the base of the TIP41A using a BS170 together with a pull-down resistor to do this.
Q2: Will this work?
Any other thoughts?
I have a good knowledge of components but only a very limited knowledge of circuit design.
Thanks in advance for any assistance.