I bought an Arduino UNO, a laser, connectors, resistors, transistors. I'm trying to hook up the laser and perhaps a few other components to eventually measure the light intensity frequency of reflected beam.
My first attempt worked for an hour or so. I hooked up the 5v power through a transistor controlled by one of the mainboard's digital pins. Burned out the laser eventually.
Bought a second laser and an assortment of resistors, but I don't know how to design the circuit properly.
I'm trying http://ledcalc.com/ to determine what resistance I should use according to the laser's specs. But I'm confused about a few things:
- How ought I power the laser properly? I burned it out (unless I burned out something else instead?) presumably because of too much ... something. Volts?
- The UNO specs seem to say that the 5V pin, when the board is powered by USB is not available as a power supply (when compared to the 3.3V pin). However, I read about 5V on my multimeter. I am unable to determine how many AMPs are available to draw as the specs don't say it, and I must not know how to read it correctly on my meter. Is it possible to measure available current between the 5V and GND without any load? My meter is an Ideal 61-310 set to DCA 200m with probes in COM and mA.
- Even if the 5V is available and offers amps, if it's in the ballpark of the 3.3V pin at 50mA, that's not nearly the 300mA that the laser is capable of. How did I burn out the laser?
- On ledcalc, with 5V input, 4.5V power drop, 300 mA (correct for the laser, I believe), I get a recommendation of 1.8Ohms. I'm also getting 1250mW power dissipation by the laser, which is not the 5mW listed in the spec.
- If I do need a transistor to control the circuit and a resistor to limit the current, does the order of the components in the circuit matter?
That's a lot of stuff, but I'm confused about a lot, and they're all interdependent.
(I have safety goggles for working with the laser)