# [HELP] 5V laser question

Joined Dec 7, 2015
3
Hello and thank you for taking the time to listen to a first time poster.

I have a bag of 5V red lasers and I'm simply looking to wire up a simple circuit with lots of them. (I'm just looking to experiment and learn - please excuse my ignorance.)

I understand wiring up LEDs in series and parallel with a calculator like this:

http://led.linear1.org/led.wiz

QUESTION: Are lasers the same? Can I wire them up the same way according to voltage/current/resistance?

I've got the lasers, transformers/power supplies (AC to DC), and the buck converters needed. I only need to check to see if I'm making a big mistake in jumping from "LEDs with X voltage are like this" to "lasers with X voltage drops are the same".

Thanks in advance for any replies or help.

#### #12

Joined Nov 30, 2010
18,224
The real answer is in the specifications of the "lasers". If they are built for 5 volts, give them 5 volts. It is not likely that the laser LED actually uses 5 volts. If it does, it already has a current limiting device installed.
As the alleged, "wizard" says,
"All you need to know are the specs of your LEDs and how many you'd like to use."

Solid state lasers are light emitting diodes. You are on the right track by calling them, "LEDs" but we can't read the specifications from here. LEDs are current driven devices. The voltage specifications are (almost) miserable as reference points because the voltage an LED needs changes from batch to batch and it changes with temperature changes. Rather than posting a calculating program that is called a wizard, you should post the specifications here because real wizards live here. The problem is that we need the same information the calculator needs.

#### hp1729

Joined Nov 23, 2015
2,304
Hello and thank you for taking the time to listen to a first time poster.

I have a bag of 5V red lasers and I'm simply looking to wire up a simple circuit with lots of them. (I'm just looking to experiment and learn - please excuse my ignorance.)

I understand wiring up LEDs in series and parallel with a calculator like this:

http://led.linear1.org/led.wiz

Why ask for theories? Build it and see what happens.

QUESTION: Are lasers the same? Can I wire them up the same way according to voltage/current/resistance?

I've got the lasers, transformers/power supplies (AC to DC), and the buck converters needed. I only need to check to see if I'm making a big mistake in jumping from "LEDs with X voltage are like this" to "lasers with X voltage drops are the same".

Thanks in advance for any replies or help.

Joined Dec 7, 2015
3
The real answer is in the specifications of the "lasers". If they are built for 5 volts, give them 5 volts. It is not likely that the laser LED actually uses 5 volts. If it does, it already has a current limiting device installed.
As the alleged, "wizard" says,
"All you need to know are the specs of your LEDs and how many you'd like to use."

Solid state lasers are light emitting diodes. You are on the right track by calling them, "LEDs" but we can't read the specifications from here. LEDs are current driven devices. The voltage specifications are (almost) miserable as reference points because the voltage an LED needs changes from batch to batch and it changes with temperature changes. Rather than posting a calculating program that is called a wizard, you should post the specifications here because real wizards live here. The problem is that we need the same information the calculator needs.

Thanks. I think that's good enough. These are simple lasers, and nothing special, so I think treating them like LEDs will work out.

#### #12

Joined Nov 30, 2010
18,224
I think treating them like LEDs will work out.
If you are going to treat them like LEDs, you need to know how much current they want. If you have that number, you can use Ohm's Law to use just about any voltage and add a resistor that will provide the correct amount of current.

One of the most absurd designs I ever saw was a UHF amplifier which used a j-fet (a current driven transistor) in the range of 30 volts and 20 ma. It was provided power from a 400 volt source by way of an 18K, 15 watt resistor. This seems absurd because the resistor used up 7.5 watts while the transistor used up 0.61 watts, a power waste ratio of over 80%! You are obviously not going to generate 400 volts to run a 5 volt LED, but the point is, it can be done if you do the math right.

#### hp1729

Joined Nov 23, 2015
2,304
Hello and thank you for taking the time to listen to a first time poster.

I have a bag of 5V red lasers and I'm simply looking to wire up a simple circuit with lots of them. (I'm just looking to experiment and learn - please excuse my ignorance.)

I understand wiring up LEDs in series and parallel with a calculator like this:

http://led.linear1.org/led.wiz

30 mA ? Like these? With the built-in lens that points in any direction but straight?

QUESTION: Are lasers the same? Can I wire them up the same way according to voltage/current/resistance?

I've got the lasers, transformers/power supplies (AC to DC), and the buck converters needed. I only need to check to see if I'm making a big mistake in jumping from "LEDs with X voltage are like this" to "lasers with X voltage drops are the same".

Thanks in advance for any replies or help.
Like these? With the built-in lens that points in any direction but straight?

3.5 V, 30 to 35 mA
Still draws about 30 mA at 5 V, so it may have a current limiter built in.

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#### mcgyvr

Joined Oct 15, 2009
5,394
I would NOT treat a device called a 5V laser like an LED at all..
An LED needs a constant current supply..
A 5V laser needs a constant voltage supply (5V)..

The 5V lasers just need to be attached to a regular 5V ac/dc power supply (5V wallwart).. Multiples simply wired in parallel right off a 5V bus.

Since you have a bag of them the easiest test is to attach one to 5V and see what happens..

Joined Dec 7, 2015
3
Like these? With the built-in lens that points in any direction but straight?

3.5 V, 30 to 35 mA
Yes - those exactly!

Except they're 5V. These: