Me and my friends are trying to build a laserharp driven by arduino as a learning exercise. Currently we are using a phototransistor to interrupt the laser light and play music.
However the activation area of the phototransistor seems to be very small and requires it to be placed quite precisely in the path of the beam.
I am unable to look for something like a large activation area phototransistors... if they exist?
Or is it possible to use some kind of lensing arrangment (which should be cheap) to focus light from a wider area to the transistor.
As another possibility, I would also like to look into solar cells. Since there area is quite adequate they are perfect for my application. However I don't know if their response time would be fast enough (close to phototransistor) and secondly from where do I get a single solar cell?
Since the laser is just a point on cell, using a solar panel is quite inadequate for my purpose.
More details: Sorry for not having them before.
I have one 8mW green laser (power is not precise, I hacked it out of a home projector.. but is getting my job done)
We incident the laser on a mirror, that is being rotated by a stepper motor. Currently 4 steps clockwise, and then 4 anticlockwise with a delay of around 4 ms on each step. This produces 4 beams of laser from a single beam.
As a pick I am currently using a phototransistor with Vcc. on the collector, and an emitter grounded through the resistance with a floating base.
When the phototransistor is used to block one of those lasers, if the laser happens to fall on the activation area of the phototransistor then it gets biased and I can read that. This combined with the step number of the stepper motor lets me determine which beam is being interrupted(realize, there is only 1 beam at a time)
The problem is that since the activation area of the phototransistor is quite small, its inconvenient to get it in line of laser. This creates a non-interactive user experience. I need to remedy this.