Laser (Max current draw??)

Other Hardware General Electronics
1

hello,

I have bought a laser from a local electronics store and its rated for 2.8 - 5.2V.
The max current draw is 25mA, I'm a little unsure what does means.

Does it mean it will be fried if more than 25mA is flowing through it??

here is the link to laser: http://www.bc-robotics.com/shop/5mw-650nm-red-laser/

if someone could please explain this to me, it would be very appreciated! :slight_smile:

thanks

2

The specification means that the laser should never draw more than 25 mA. As long as the power supply voltage is between 2.8 and 5.2 V, you are safe.

3

The max current draw is 25mA, I'm a little unsure what does means.

It means that you need a power supply (or batteries) capable of delivering at least 25mA (which almost any power supply can) and since that's the maximum it can be used to calculate "worst case" battery life.

Does it mean it will be fried if more than 25mA is flowing through it??

The only way you'll get more than 25mA is if you over-voltage it. The current is determined by the load ([u]Ohm's Law[/u]).* i.e. A 100W / 120VAC light bulb "draws" about 0.8 Amps. A 1200W hair dryer draws 10 Amps.

  • An LED (or a "raw" laser diode without a power supply) is non-linear (the resistance changes with voltage) so you need a constant-current source, and you can easily fry an LED or laser diode. The laser with it's power supply is probably somewhat non-linear too, so that you get approximately the same light output when the voltage varies (as long as the voltage remains within spec).
4

oh okay!!

thanks!!!

5

so just to clarify, if i wear to use 9V battery to power my laser, i would use 25mA to find the resistor necessary to drop the voltage to a value i needed?

(9-3.5)V / .025A = 220 ohms

thanks for all the help! :slight_smile:

6

Since the current drawn by the laser is only specified as a maximum, you be better using a voltage regulator
to avoid damage.

Allan

7

okay. thanks for the help!!!

8

allanhurst:
Since the current drawn by the laser is only specified as a maximum, you be better using a voltage regulator
to avoid damage.

Allan

i am taking your advice of using a voltage regulator.
i was watching some youTube video for some help with the regulators,

all the video say to you some capacitors and i dont understand why??

here is one video i was looking at: https://www.youtube.com/watch?v=4SR4uVW--LE

thanks for the help!

9

You need capacitors to stop the regulator oscillating. They are compulsory.

The minimum exact value is given in the data sheet of the actual manafacature of the regulator you use.

10

one last question:

is there a specific value i should use for the capacitors?

11

Read the datasheets.

Allan

12

WhiteT:
one last question:
is there a specific value i should use for the capacitors?

What part of:-

Grumpy_Mike:
The minimum exact value is given in the data sheet of the actual manufacture of the regulator you use.

are you having difficult understanding.

Also please read this:- Sam's Laser FAQ - Diode Laser Power Supplies
Things might not be as straightforward as you might think.