Automatic Device Locator (Beacon)

Table 1
Part Description Radio Shack Digi Key Notes
IC1  LM555 timer/oscillator  276-1723    NE555, etc.
Q1  2N3904 transistor      NPN-50V-150mA
R1*  3M3 resistor    3M3QBK-ND  orange orange green gold
R2  1K resistor     1KQBK-ND  brown black red gold
C1*  220µF, 16V capacitor      electrolytic (see text)
C2  220µF, 16V capacitor      electrolytic

A Couple of Final Notes:

o All partnumbers are Radio Shack/Tandy or DigiKey unless otherwise indicated.

o All resistors are minimum 5%, 1/4 watt, carbon, unless otherwise indicated. It's okay to use metal film or other precision types. 3M3(R1) is the same as 3.3M

o With this circuit you can find your aircraft easily in high grass, corn fields, soybeans or whatever. As soon as you power on your receiver the timer will start to count down.

o If you power the unit via the receiver battery, make sure to purchase a 3 - 6 volt buzzer! Remember that in the case of a crash (heaven forbid!) the receiver may loose its power from the battery pack because of the force of impact. It would be safer to provide the ADL with a 9-volt Alkaline battery + on/off switch and wrap the whole thing in 1/4" SIG latex rubber.

o The timer, with the components shown above, goes off in about 18 minutes at 9-volt. To increase the delay, increase the value of R1. Also, R1 could be made adjustable with a 5-Mega-ohm trimpot of the proper wattage.

o A CMOS version of the 555 timer is available (MC1455P1), and preferred, which will cut the powerdrain on battery powered circuits. The MC1455P1 is pin-compatible with the NE555, and most other 555 chips. C1 and C2 are electrolytic capacitors (or tantalum) so watch the '+' and '-' orientation. Q1 (2N3904) can be most any substitute so it's not critical; just watch the position of the emitter/collector as some european type have them reversed (like the BC types).

o The ADL can be used for all forms of R/C equipment, the only thing needed may be to adjust the delay to tailor your needs.

o This device is tested for interference with JR, Futaba, HiTec, Airtronics, Hobbico, and ACE radio equipment. None were found and none are expected when used with other brands of Radio equipment.

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Copyright © 1996, Tony van Roon