Automatic Device Locator

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:

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

oAll 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

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

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

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

oA CMOS version of the 555 timer is available (MC1455P1), andpreferred, 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 assome european type have them reversed (like the BC types).

oThe 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.

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

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