Building a laser detector

Device specs:
•On/off button
•green light
• speaker
•laser sensor
•LED lights or flashing LED lights

-The device reacts to the any laser( for now)
-the sensor needs to react the laser up to 25feet. Currently, I have the Stanley laser level.

Function:
The laser crosses the sensor on the device which activates the speaker(alarm sound) and LED lights simultaneously. When the laser is not touching the sensor, nothing happens.
When the device is on, the green light is activated. As long as the laser is on the sensor, the LED lights and the speaker will stay activated. They stop only when the laser doesn't touch the sensor on the device.

Here's the list gathered so far for the build:
•Arduino micro controller
• sensor
• micro speakers
• proto board
• little connection circuit cable.
Someone mentioned to me I need a specific micro controller, which one?
I have a hard time finding the exact sensor that I need. Can someone please point me to the right direction?
A link to what I need is very appreciated.

Thank you

Why do you need a micro controller? The whole thing can be done with a few transistors.
How is the unit to work in the field. If you move the laser until you align it with your detector, you will need to have a stable platform with screw adjustment on the azimuth, or you will end up with so much vibration that you will have trouble finding the detector. It helps if you have a large area photo detector (expensive) but your resolution is then limited to the diameter of the detector, and since the spot size is a lot smaller than the detector area, efficiency is lowered. Another option is to have a number of smaller detectors which allows you to find the target and then make fine adjustments to reach the target detector. It would help if you described what you are wanting to achieve with the device.
Photo detectors are readily available, and with a few milli watts of laser power, you won't need much sensitivity. You will probably need to exclude sunlight from the detector though, a simple optical filter may help. Do the maths, you know the laser power.
Any company supplying electronic components will supply photo diodes. Try RS Components and Element14 for starters.
Hope that helps,
cheers,
Richard

Wouldn't using a microcontroller be the end all be all solution? Doesn't limit range of functions. http://au.rs-online.com/web/p/processor-microcontroller-development-kits/8659007/

Initially this is a mechanical, optical, and analogue processing problem. If they can't be solved, then a microprocessor will be of no help what so ever.
Like a lot of the problems presented in this forum, not enough information has been supplied to enable a clear solution, but initially, the three items I have listed need to be solved first, any functionality that a micro may provide is the last part of the equation, and as I said, may be completely unnecessary,
cheers,
Richard

Microcontroller
For a project like yours, the choice of a microcontroller (MCU) largely depends on the complexity of the device, the number of input/output peripherals you need (like GPIOs for the sensor, speaker, LED lights, and the green light indicator), and any additional features you might require (such as PWM outputs for LED dimming or speaker volume control).

Arduino Uno is a robust choice for beginners and prototypes. It's based on the ATmega328P and offers a good balance of GPIO pins, is easy to program, and has extensive community support.

Arduino Nano or Arduino Micro could be more suitable for a compact design. Both are based on the ATmega328P (Nano) or ATmega32U4 (Micro), similar to the Uno but in a smaller form factor. The Micro, in particular, could be advantageous as it comes with built-in USB functionality, making it easier to design a compact device.

Sensor for Laser DetectionThe sensor to detect a laser beam can vary based on the type of laser (color/wavelength) you're using and the required sensitivity. Since you're working with a commercial laser level, which typically uses a red or green laser, a photodiode sensitive to the specific wavelength of your laser would be appropriate.

Photodiode: Look for a photodiode with high sensitivity to the wavelength of your laser (650nm for red, ~532nm for green). Photodiodes are fast and can detect laser light from a distance, but you'll need to amplify the signal for the Arduino to process it effectively.

Phototransistor: These are generally more sensitive than photodiodes and can provide a stronger signal in response to the detected light, potentially simplifying your circuit. However, they might be slower, which is usually not a problem for an application like yours.

Light-Dependent Resistor (LDR): While not as precise or fast as photodiodes or phototransistors, LDRs are easy to use and can detect changes in light levels. They might not be the best for detecting a laser from 25 feet away, especially in varying light conditions.

Implementation Tips
Amplification: A simple amplifier circuit using an operational amplifier (op-amp) might be necessary if the signal from the photodiode or phototransistor is too weak for the Arduino to detect reliably.

Filtering: To improve the reliability of the sensor, consider using optical filters that match the wavelength of your laser. This can help reduce false triggers from ambient light.

Debouncing: Implement software debouncing for the sensor input to avoid false triggers caused by noise.

Adjustable Sensitivity: Adding a potentiometer to adjust the sensitivity of your sensor circuit can help you fine-tune the device's response to the laser.

Programming: Your Arduino code should monitor the sensor's output. When the sensor detects the laser, the code should activate the speaker (using a digital output or PWM for sound generation) and the LED lights. Use another GPIO pin to monitor the state of the on/off button and control the green indicator light.