Simple Question on Resistors

Other Hardware General Electronics
1

Hi All,

I'm going to be plugging in a 5V laser beam for a break beam and the specs say this.

Rated output current 10mA max
Supply voltage Receiver: 5Vdc, sender: 3.3-5Vdc
|Insulation resistance|50 MΩ min. at 500 V DC between energized parts and case|
|Dielectric strength|1000 VAC max., 50 / 60 Hz for 1 min between energized parts and case|

If powering from Arduino - what type of resistor would I need for this?

Also, if I was to connect 5 of these lasers, would I put the same resistor for each one or would the resistor needed change based on the number of lasers.

Thanks

2

Don't. Add a separate power supply to feed just the lasers. Arduino is not a power supply for peripherals, other than a few LEDs or an LCD display. Connect the laser power supply ground to Arduino ground.

The specs should state somewhere how much current the laser unit will need from the power supply to operate correctly.

What's the proposed function of the resistor(s) you mention?

3

Can you post a link to the source of the data?

4

http://bit.ly/44v4Klp

Link above

5

To avoid sending too much current to the sender/receiver.

Maybe it's not needed, but when I was learning about the basics I needed one for LEDs to avoid sending too much current.

6

You connect a 10K resistor between the receiver black and brown wire, one for each receiver.
Also connect the brown wire to 5V and the blue to ground (GND).

You can connect all the senders (LASER) together to a 5V supply.

1 Like
7

One that works?

8

Just edited to make it work

9

Just to confirm:

Brown - to 5V supply (not from Arduino) w/ a 10k resistor. (would it matter on the 5v supply? i.e. if it provides 200mA vs 800mA should I use the Ohm's law calculator?)

Blue - to Arduino ground

Black - to digital pin on Arduino w/ a 10k resistor

10

For the receiver:

BROWN --> Arduino 5V
BLUE --> Arduino GND
BLACK --> Arduino Digital pin
10K Resistor: Connect between BROWN and BLACK

For the sender:

If you use ONLY ONE, you can connect it to the Arduino 5V
BROWN --> Arduino 5V
BLUE --> Arduino GND

If you use MORE than one, then you need a separate 5V supply
All BOWN --> +5V
All BLUE -- Power supply Ground or -5V.

1 Like
11

The resistor between the brown and black wire is a pullup resistor. Without it, the black wire will read 0V or will be floating ( some voltage between 0 and 5).

The current limit for the black wire is 10mA. So using ohms law, the smallest resistor you could use is, 5V/10mA = 500 ohms.
However there is no need to draw so much current, a 10K will also work, 5V/10K = 0.5mA.

1 Like
12

Thank you so much!!!

13

You're welcome.

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