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Hardware list and description
Since you can customize your own tagger system and the price for the components varies depending on time and distributor, the overall price cannot be given exactly. I will list here some possibilities and prices, for which I've found the components on websites like amazon or aliexpress at the time of writing this article (2017). These prices contain no warranty and can change at any time. I will not update this page, if the prices change.
For components like the arduino nano, it's far cheaper to order them directly from Asia through aliexpress, though you have to deal with delivery times of up to 2 months. When using aliexpress I prefer getting the products with free shipping, since, with the small number of articles a maker buys, the lower prices cannot make up for the shipping costs.
Components needed for the tagger (without receiver modules)
| Component | Supplier | Package | Needed Number | Prize p. package | Prize p. component |
|---|---|---|---|---|---|
| Laser module 5V (5mW, better less) | aliexpress | 10 | 1 | 1.86€ | 0.19€ |
| Arduino Nano v3 (china clone) | aliexpress | 1 | 1 | 2.00€ | 2.00€ |
| IR diode 5mm (about 950nm) | aliexpress | 20 | 1 | 0.93€ | 0.05€ |
| I²C Port Expander PCF8574A | aliexpress | 10 | 1 | 14.02€ | 1.40€ |
| RGB LED 5mm (common cathode) | amazon | 50 | ca. 6 | 3.57€ | 0.07€ |
| Bipolar transistor NPN (standard model) | amazon | 100 | ca. 6 | 1.75€ | 0.02€ |
| HC06 Bluetooth Serial Module | aliexpress | 1 | 1 | 2.62€ | 2.62€ |
Components needed for each receiver module
| Component | Supplier | Package | Needed Number | Prize p. package | Prize p. component |
|---|---|---|---|---|---|
| IR Receiver TSOP4838 | aliexpress | 10 | 3 | 2.99€ | 0.30€ |
| ATTiny85 | aliexpress | 10 | 1 | 10.47€ | 1.05€ |
| I²C Port Expander PCF8574A | aliexpress | 10 | 1 | 14.02€ | 1.40€ |
| RGB LED 5mm (common cathode) | amazon | 50 | 3 | 3.57€ | 0.07€ |
| Bipolar transistor NPN (standard model) | amazon | 100 | 3 | 1.75€ | 0.02€ |
Since laser light is highly dangerous for the human eye, you have to be very careful when you equip your tagger with a laser gunsight. For preventing eye damage, when playing, the output light power of the light must not exceed 1mW, which is considered save for visible light (since the eye is closed fast enough)(still you have to be careful. Don't use them outside, since the light can blind pilots and car drivers). Unfortunately it is difficult to buy laser modules with power of 1mW. Instead you can buy 5mW laser modules for very cheap prices. To reduce the power of these modules we can use an optical polarization filter. You can get these from the glasses you get in a cinema for a 3D movie (those you have to buy for a few euros before the movie starts) (most cinemas are using polarizing glasses. If the glasses in your cinema are somewhat heavy and the glasses don't consist only out of a simple plastic material, you cannot use these. Those shutter glasses have to be returned to the cinema after a movie).
When you are holding the polarizing filter in the laser beam and rotating it around the beam axis, you will see, that the light intensity goes nearly to zero at a certain angle. The intensity follows a sin(φ) function, where φ is the rotation angle measured from the zero intensity angle. At 90° the intensity is maximal. So, when we want to reach 1mW out of 5mW of light power this makes a ratio of 0.2 = sin(φ) ⇒ φ = arcsin(0.2) = 11.5° So we have to adjust the polarizing filter at an angle of 11° or lower from the zero intensity angle.
Alternatively you can drive the diode with less voltage, but you have to check, that the output power is low enough (e.g. through comparison with a diode, whose power is reduced with the polarization filter).
Initially I used the ATTiny45 for this project, but the code grew bigger, so you need the 85. When looking for the best suppliers, I found that the ATTiny85 (which is basically the same microcontroller as the ATTiny 45, only with more memory) is a little bit cheaper than the 45.
When searching for the Arduino Nano at aliexpress, you will find the way cheaper clones from china. These are as good as an original Arduino for this project.