Can't figure out how to power KY-008 5v laser modules

Projects General Guidance
1

Hi all, I'm using KY-008 5v laser modules in an Elegoo UNO laser harp build for a theatre performance, first performance is on Friday. I'm finding that the diodes are dimming/dying when powered by USB (in hindsight this should have been obvious! Still learning).

I have a 5v (3A, center positive, 100-140VAC, 50/60hz) and am trying to figure out if I can use that to power the laser modules, or whether there's another way I can do it.

Current setup:

  • Elegoo R3 Uno on breadboard, +/- going to breadboard rails
  • 1 photoresistor per laser module, analog output going to one row of breadboard rail, each row is wired with a 5.6k resistor in between
  • Each module individually wired in to +/- rails

Any help would be greatly appreciated!

2

Hi! Welcome to the Forum.

When powered by USB, the Uno is able to use 500mA max. including the current on the 5V pin. If your harp has multiple Ky-008 modules and/or other sensors, most likely your Uno is not up to the task.

Yes, derive 5V from the wall adapter to feed the modules can solve the problem.

Please:

  • tell us how many laser/photoresistor pairs do you have.
  • tell us if there are other things connected to the Uno
  • provide an annotated schematic (hand drawn is fine) showing how is everything connected.
3

Hi,

Thank you so much for the assistance! I have six pairs of laser modules and photoresistors.
Nothing else is connected to the Uno

            USB
             β”‚
    β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”
    β”‚  Elegoo Uno R3    β”‚
    β”‚                   β”‚

A0 ─────┼───┬──────── LDR ───── +5V rail
β”‚ β”‚
β”‚ └── 5.6kΞ© ─── GND rail

A1 ─────┼───┬──────── LDR ───── +5V rail
β”‚ β”‚
β”‚ └── 5.6kΞ© ─── GND rail

A2 ─────┼───┬──────── LDR ───── +5V rail
β”‚ β”‚
β”‚ └── 5.6kΞ© ─── GND rail

... repeat for A3–A5 ...

GND ─────────────────────────── GND rail
β””β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜

    LASERS (x6)
    + ───────── +5V rail
    - ───────── GND rail.

Powering the laser modules separately would be ideal, I have lots of other sizes of resistors etc. but don't know how to proceed.

4

Like this ?

image
image560Γ—486 20 KB

  • Show us closeup images of your module.
5

laser1
laser11920Γ—2560 536 KB

laser2
laser21920Γ—2560 979 KB

Thanks Larry. Yes, that's the one. They draw <40 mA from what I'm seeing

The features and specifications of the KY-008 laser module include the following.

  • KY-008 is a 3-pin laser module.
  • This module’s operating voltage ranges from 3.0V to 5V.
  • Its operating current is 40mA.
  • Its output is a red color laser beam.
  • The wavelength is 650nm.
  • The transmit power is 58mW.
  • The line length is approximately 135 mm
  • Its size is 12.0 x35mm
  • Its outer diameter is 6mm
  • Output power is 5mWatts.
  • The wavelength is 650nm.
  • Operating current is < 40mA.
  • Operating temperature ranges from -36β—¦C to 65β—¦C.
  • Working temperature ranges from -10Β°C ~ 40Β°C.
6

You should get a 5V 2a AC adapter.

Connect together: ( try with one laser first, then connect all the others).

  • Laser 5V and the UNO 5v and the A/C adapter 5V
  • in one of connection, connect all the laser grounds and the 5V ground. Then from that connection a single wire to the UNO ground.
  • Connect the UNO outputs to the signal control of the lasers.
7
  • I use these with a driver transistor.
  • An NPN BJT (2N2222) or an N Channel MOSFET like the (SOT23) Si2302 will work.
8

image
image1166Γ—755 180 KB

I swear I prefer a schematic, but that might do…

Each signal pin of the laser modules should be connected to one arduino pin if you want to turn them on/off at some point. Otherwise, signal might be connected to +5V and the lasers will be on all the time.

EDIT: see post #23

9

Hi, @final_aminal
Welcome to the forum.

Do you have a DMM? (Digital MultiMeter)

Thanks.. Tom.... :smiley: :+1: :coffee: :australia:

10

Hi John, thank you! Could I remove the barrel plug from my 5v 3A adapter and strip the ground and power wires and then run each of those to a separate row of stripboard/breadboard?

And then connect the stripboard ground to the Uno ground and the 5v stripboard row to the Uno 5v row, and connect the lasers to the respective rows?

11

Thank you! I think due to time constraints (entirely my fault) I might be unable to get those in time, am I right in saying that this is for switching the lasers on and off? I'm hoping to use the 5v 3A adapter to power the lasers and then just plug it in and out to turn the lasers on/off, I'm just not 100% sure how to go about it. Do you think I could remove the barrel plug and connect the 5v and ground wires to breadboard rail/stripboard rows as well as the 5v and ground of the Uno and then connect the lasers to the respective rows?

12

Apologies for the bad schematic Brazilino! I'll draw one up. Thanks a million for the detailed schematic, I wasn't sure how to do that, I see what you mean. I think (and hope!) the lasers don't necessarily need to be switched on/off if I can just plug the adapter in/out manually to achieve that, does that make sense? I haven't worked with them before. I was thinking of stripping the adapter wires and running them directly to the breadboard and 5v/ground pins.

13

Hi Tom, I do indeed!

14

That does make sense.

These modules have 3 pins (+,- and S). The β€œS” pin, which stands for β€œsignal” is the one that turns them on and off. On when applied a β€œHIGH” signal. Off when applied a β€œLOW” signal. So, to keep the lasers β€œon” as soons as you plug the adapter on the wall, the S pin should be also connected to +5V line.

15

After reading again your anwers, this picture came to my attention:

image
image421Γ—610 46 KB

Here you have a wire connected to (-) and one wire connected to (S). Nothing is connected to the (+) pin.

I don’t have a module like this here to test what would happen, but if the module was parasite powered via S pin, this can also explain the dimming.

EDIT: see post #23

16
  • Do you intend to turn the lasers on and off ?
17

Hi,
I think this has come up before, the laser is a two wire device on a generic three wire sensor PCB.
If you look closely you should be able to trace the PCB track from the Laser Unit to the two of the three pins it is connected to.

Tom.... :smiley: :+1: :coffee: :australia:

18

I hope not.

19

Is your old 5V power supply a 50 Hz transformer with mid to plus and both sides with diodes to minus?
Does ot have large caps? (4700 uF at least))
Does it have regulators?
Depending on its old purpose it may have a lot of ripple and a rms voltage of 5V, but higher voltage at peak. I would not recommend that for your lasers.
Instead: use an old phone charger. From your drawer where these tend to pile up, or maybe from the junk shop.

20

That's 240mA

So that should not be the problem. The Uno itself and your LDR circuits won't even use 100mA in total.

The diming problem must be something else.