Reed Switches with a laser

Hi guys.

I have a simple circuit that is giving me a bit of a headache.

I do not have a picture nor can I get my hands on one that you would be able to see anything of use from, however it is so simple that I can describe it exactly.

+5V --> Reed Switch 1 --> Reed Switch 2 --> Reed Switch 3 --> Reed Switch 4 --> Laser --> Ground

That is the entirety of my basic setup. When magnets are placed over each reed switch the laser activates as it should.

However I am trying to add a sound that plays when the laser comes on. I thought I could just run a wire that connects between the fourth reed switch and the laser to a pin on the arduino uno that will read a HIGH and play my required sound(through an attached wave shield, the sound isn't the issue so much as spurious HIGH readings.)

Initially this didn't work and I had(I think) a floating voltage so I pulled the pin to ground through a resistor(I tried many values from 1M ohm to 56 ohm). While this locked the initial reading at "0" or LOW I could never get it to go HIGH when the reed switches were all activated.

I also tried to make my arduino pin HIGH using the INPUT_PULLUP and ran the wire from between the 4th reed and the laser to the IN pin on a 5V relay board. I ran the arduino pin to the relay to ground so that when it tripped the pin was pulled low. This gave me the only good results of my work but I am still getting some spurious readings and it seems like my relay board is showing that it has(at least some) power going to it all the time and just gets enough of a boost when the laser is activated to make the relay trip. Whatever this issue is, it also makes the other relays on the board buzz when activated.

Anyone have an idea why there is power present in my initial setup at the point I mentioned even when the reed switches are not activated.

Thanks for any help.

It would be good to draw a picture of the circuit and post it. What you have described says nothing about the power supply for either the arduino or laser, how long the wires are in the circuit, how you hooked up the pulldown resistor, or whether you connected grounds if using separate supplies. What about the laser diode? How much power does it require?

With such a simple circuit, there are many variables.

+5V --> Reed Switch 1 --> Reed Switch 2 --> Reed Switch 3 --> Reed Switch 4 --> Laser --> Ground

If I understand that correctly you have 4 switches in series so the laser only comes-on when all 4 switches are on (closed)?

I also tried to make my arduino pin HIGH using the INPUT_PULLUP and ran the wire from between the 4th reed and the laser to the IN pin on a 5V relay board.

Which switch terminal did you connect to?

You shouldn't need a pull-up since the 5V is a "hard" pull-up. You may need a pull-down, but I wouldn't think so.

The connection directly to the laser should go high (5V) when the laser is on and low (0V) when the laser is off. Do you have a multimeter to check that?

If the 5V connection to the laser is power, it should give you a "solid" low when off. If it's an enable or trigger input, there is a chance that there is some other short-duration signal there, but that's unlikely.

Is the laser 5volt or have you put a resistor somewhere in series with it? If so, where?