So, something about this doesn't look right:
1,2 EN = Arduino's 5V
1A = PWM control signal
1Y = 3 TSAL6200 IR LEDs in parallel -> 100 Ohm resistor -> Arduino's ground
VCC1,VCC2 = Arduino's 5V
GROUND = Arduino's ground
For one, I am just now noticing that the TSAL6200 is rated to a max of 1.6V while I've been running at 5V (Nothing exploded). Given that the SN754410 is rated for a minimum 4.5V (maybe not the most appropriate part) I might have to step down the voltage on the output like this.
Second, it appears while the digital IO pin on the Arduino (what I am currently using) maxes at 40mA, the 3.3V line only does 50mA. There is no max listed for the 5V pin but one can assume comparable. This would imply I really can't drive the max amperage for the 3x LEDS (100mA each).
So, lets start again for an easy to acquire ~4.5 V supply, divide by 3 to be within the TSAL6200's max voltage, and add a draw of 300 mA:
Ohm's law:
0.3 A = 1.5V / x Ohm
5 Ohm = 1.5V / 0.3 A
Voltage Divider:
1.5V = ( Z2 / ( Z1 + Z2 ) ) * 4.5V
1/3V = ( Z2 / ( Z1 + Z2 ) )
I am guessing here but I think we want Z1 = 5 Ohm. With little confidence that is correct lets keep going:
Update: I've been corrected and we want Z2 to be 5 Ohm, see the comments for the new result.
1/3V = ( Z2 / ( 5 Ohms + Z2 ) )
5/3 Ohms + Z2/3 = Z2
5/3 Ohms = Z2 * 2 / 3
5 Ohms = Z2 * 2
2.5 Ohms = Z2
This gives:
1,2 EN = Arduino's 5V
1A = PWM control signal
1Y = 5 Ohm resistor -> 3 TSAL6200 IR LEDs in parallel -> Battery ground
-> 2.5 Ohms -> Battery ground
VCC1 = Arduino's 5V
VCC2 = 4.5V Battery
GROUND = Arduino's ground
So, where did I do it wrong?
