Construction and testing
An actual-size, single-side PCB for the lost plane finder circuit is shown in Fig. 3 and its component layout in Fig.4. After assembling the circuit on a PCB, enclose it in a plastic case. A tiny perfboard is enough for the construction of the lost plane finder system. After construction, it is better to make the system vibration proof with the help of a heat-shrink tube, preferably a transparent type with appropriate diameter. Connect the finished system to any unused channel of your radio receiver through the input connector (CON2) as shown in the wiring diagram in Fig. 5.
If a free radio receiver channel is not available, the system can still be utilised by sharing an occupied channel with some other intermittently-used control like landing gear, flaps or airbrakes, with the help of a Y- Splitter servo cable attached to such a channel.
The preferred setup in the model aircraft suggests drilling a small hole in the model wall and attaching the system so that its sounder window is aligned with the hole. Depending on your aircraft model’s structure, the whole system can be completely exposed outside of the model, too. Author’s prototype is shown in Fig. 6.
1. Prototype was tested with R/C lithiun-polymer 2S battery (7.4V).
2. Offline test is possible by feeding servo pulses to J1 from a standard servo tester.
3. An intermittent-tone piezo buzzer (sound level 85dB to 92dB) is better than a continuous-tone type.
4. In case of an alarm malfunction, change the value of RC components (R2-C2) so that effective delay is about 30 per cent to 40 per cent bigger than the period of inputted servo pulses.
5. For a micro-size version, try to use SMD components on a stamp-size PCB.
Download PCB and component layouts: click here
T.K. Hareendran is founder and promoter of TechNode Protolabz