Hi, I'm new here and wanted to check the feasibility before getting an Arduino.
I’m working on a university project in which a part consists of detecting a laser, tentatively using a Thorlabs DET36A2 detector. When illuminated, that detector will generate current.
The manufacturer’s intended usage is to attach a 50 ohm coax cable via a BNC connector, attach a 50 ohm terminator at the other end and then connect to a voltage measurement device of choice.
Our intended usage is rather to attach the detector to a computer and whenever the detector is illuminated (i.e. whenever it produces current), the computer would play a sound.
Obviously, we can’t connect this laser detector directly to a computer, we need some kind of hardware in between, that’s why I stumbled upon Arduino and I have a few questions:
How would I connect the Thorlabs DET36A2 to the Arduino, i.e. the other end of the 50 ohm coax cable?
Can the Arduino then send a signal via USB to the computer, as soon as it receives the current?
Suggestions of another laser detector that would be better suited to work with the Arduino?
(I realise there would be programming required, both for the Arduino as well as for the computer, to make this work.)
It looks like the bias voltage of the is 5V so you could just connect the coax to an anlog input pin as well as a 50 ohm load resistor tied to ground and then just measure the voltage at the pin
As for playing a sound, you could do that with the arduino as well. Look at the DFMini MP3 player which can be controlled by the arduino and you can put any sounds you like on the SD card. If you would rather connect it to a PC, then it appears as a serial device (COM3, COM4,... ) that can communicate with a program on the PC.
How long is the coaxial cable? The output says "0-10mA" in the manual. Across a 50 ohm resistor, that would develop a voltage of 0-0.5V. The Arduino could read that but it's low. If your cable is short, you can use a higher resistance and get a higher output.
If all you need is something to play a tune with the light beam, this seems like a lot of overkill. The unit has a battery that will die after a period of use. There are many much simpler detectors that don't use a battery (or could take power from the Arduino).
The laser detector is optimized for high speed data transmission, not for hit detection. Which kind of laser signal do you want to detect? Wouldn't a LDR be easier to use?
Higher termination resistors can be used, with reduced bandwidth.
Laser on - computer plays a sound
Laser off - computer silent
Sounds like the timing is not critical. If the sound is a ring tone, it may play to the end, right? Or should it stop in the middle, when the laser goes off? In any case, you don't want the sound to switch on and off in a few milliseconds intervals, right? So an LDR would be just fine.
You can set AVR-chip (8-bit, 5V) Arduino analog converter to use the built-in 1.1V Ref. A read of 1023 = 1.1V or more.
LDR is slowwww, takes milliseconds to change. You can average fluctuating light with one, the response is dismal.
LDR Summary
Resistance decreases with increasing light levels. Typically > 1 MΩ when dark and < 1 kΩ in high light levels. Response time of 2 – 50 ms. (Much slower than photo-transistors.)
Light dependent resistor (LDR) | LEDnique
Better to use phototransistors, they are fast and can strengthen the signal.
Arduino came from a book named Processing and Wiring. Arduino is Wiring.
Before Arduino a PC language named Processing was started. It is similar to Arduino.
You can get Processing 3 at processing.org and do amazing things. Include the Serial Library to comm via USB.
I understand that Python can also be used and there's likely others as well. It's about getting to the COM ports.