Hello:
I am new to this forum and a beginner with electronics. I have a project I am working on and have many questions.
I am powering this laser: https://www.sparkfun.com/datasheets/Components/Laser-Card.pdf
Input Power Source: DC3.1V±10%
Consumption Current: typical: 35mA, Max: 40mA
I am using an Arduino uno as the power source. This is a 5v power source.
On http://www.overclockers.com/forums/showthread.php/175036-Basic-Electronics I read that the formula for powering an LED is E/I=R, where E=volts, I=amps, and R=resistance needed(ohms). The poster takes the power supply and subtracts the power consumption to come up with E.
I assume this is the same for powering my laser. Two questions:
1. So 5v - 3.5v = 1.5v and 1.5/.035 = resistor size. 42.857142857ohm. I need to use a 43ohm resistor to power a laser.
Is this correct?
2. Playing around with a digital multimeter. I read the voltage coming from arduino uno at 4.56v. I then add a 120ohm resistor (brown red brown gold) on the gnd side and read the voltage again. It reads the same.Shouldn't it change the voltage? Isn't that what I use a resistor for? I need to bring the voltage down to the 3.5v range for the laser don't I?
I am new to this forum and a beginner with electronics. I have a project I am working on and have many questions.
I am powering this laser: https://www.sparkfun.com/datasheets/Components/Laser-Card.pdf
Input Power Source: DC3.1V±10%
Consumption Current: typical: 35mA, Max: 40mA
I am using an Arduino uno as the power source. This is a 5v power source.
On http://www.overclockers.com/forums/showthread.php/175036-Basic-Electronics I read that the formula for powering an LED is E/I=R, where E=volts, I=amps, and R=resistance needed(ohms). The poster takes the power supply and subtracts the power consumption to come up with E.
I assume this is the same for powering my laser. Two questions:
1. So 5v - 3.5v = 1.5v and 1.5/.035 = resistor size. 42.857142857ohm. I need to use a 43ohm resistor to power a laser.
Is this correct?
2. Playing around with a digital multimeter. I read the voltage coming from arduino uno at 4.56v. I then add a 120ohm resistor (brown red brown gold) on the gnd side and read the voltage again. It reads the same.Shouldn't it change the voltage? Isn't that what I use a resistor for? I need to bring the voltage down to the 3.5v range for the laser don't I?