The Circuit
Below are links to the circuit diagrams for the Libre Tag system:-
The main diagram showing the Gun, sensor and power supply
Libre Tag Circuit – Rev A
Parts List
Name | Value |
R1,R12,R13,R15,R17 | 1K |
R2,R3,R4,R5,R6,R8 | 10K |
R7 | 20K |
R8,R9,R10 | 100 |
R11,R14 | 20K |
C1,C2 | 100uf |
C3 | 10uf |
Q1,Q2,Q3 | BC548 |
Q3,Q4 | Logic Level FET |
XU1 | LE50CZ LDO REG 5V 0.1A |
IR LED | An Infrared LED |
LED 1 | Hit LED |
LED 2 | Muzzle Flash |
The IR LED needs to match the wavelength of the IR recievers. These two parts below from Rapids are what I have been using and suit each other well:-
http://www.rapidonline.com/Electronic-Components/Optoelectronics/Infrared-Devices/Matched-T1-frac34-infrared-emitter-and-detector-pairs/29406/kw/58-0442
http://www.rapidonline.com/Electronic-Components/Optoelectronics/Infrared-Devices/Infrared-photo-modules-38kHz/71292/kw/55-0901
These exact part numbers may not be available from your supplier. The 3 main things you need to check are:-
- As above the wavelengths of the IR LED and Receiver must match
- The viewing angle of the IR LED needs to be suited to the focal length of your lens. A half angle of 10 degrees works quite well with a 50mm lens
- The LED needs a pulse power rating of a couple of amps