I am thinking about building a laser game with a laser-pointer “gun” and a round target with a couple of concentric sectors (e.g. 1-10 and bull’s). In a first step, the target should be able to detect where the laser hit it.
My first idea is to arrange several photoresistors into a round area and then calculate the approximate point of impact by reading out all the sensors. There are several problems with that though. First, even with a Mega, the number of analog pins (and thus photoresistors) is quite limited, so the target could only be very small. Second, there will be gaps between the photoresistors, so in the worst case, the read value may not exceed a certain threshold needed to account for normal light variation, and the shot won’t register.
Has anyone of you ever tried something similar and has a better way to build such a target? Do you think it is even doable (especially as a software engineer, not an electrical engineer)? My alternative is to build a target with a single photoresistor that you either hit or miss, but I like the other idea a lot better =).
The other thing to consider with your approach is that, irrespective of the number of analogue inputs, there's only one ADC, so getting around all (say) 16 is going to take more than one and a half milliseconds.
I once saw a "live fire" tactics trainer that used a laser in the handgun barrel, triggered by the flash and shock of a blank round firing.
The target(s) was a vest, woven with a mesh of "leaky feeder" optical fibre, which was capable of registering hits with a fair degree of accuracy.
I didn't ask the price.
AWOL:
The other thing to consider with your approach is that, irrespective of the number of analogue inputs, there's only one ADC, so getting around all (say) 16 is going to take more than one and a half milliseconds.
Hmm, that's right. The gun shot will most likely set the laser high for a couple of ms, but the beam will of course travel around the target in that time.
AWOL:
I once saw a "live fire" tactics trainer that used a laser in the handgun barrel, triggered by the flash and shock of a blank round firing.
The target(s) was a vest, woven with a mesh of "leaky feeder" optical fibre, which was capable of registering hits with a fair degree of accuracy.
I didn't ask the price.
Very interesting input, thank you! I will look into it, but this may actually superseed my knowledge of electrical engineering
That's a tough one. Light sensors are usually built as small as possible because you usually want to have a tight beam between emitter and sensor or you're measuring something like sunlight or a photo flash where you want to know what the intensity is "here" and not anywhere else.
I expect that laser-tag type games use a broad laser beam and just enough sensors that the beam will hit at least one if aimed correctly. That may suggest a solution to your problem: get a "hit" on 2-3 sensors and then you know it's centered on the geometrical center of those sensors even if there isn't a sensor on that spot.
Photo resistors are relatively slow and insensitive. You can't use them to detect a coded pulse so you can't differentiate a wanted laser flash from someone lighting a cigarette nearby. Phototransitors are probably closer to what you need. I'm sure someone has built a circuit to aggregate many phototransistors into one input pin.
