
Parts List
R1 = 330K C1 = 4.7 uF/16volt
R2 = 390K C2 = 2.2uF/16volt
R3 = 68K C3 = 100nF, ceramic
R4 = 33K C4 = 100uF/16volt
R5 = 33K C5 = 47nF, ceramic
R6 = 68K LS = 8 Ohm, 0.25 - 2watt. Others may work too.
S1 = on/off switch
Re = Reed Relay (glass tube)
IC1 = NE556 (or use two 555's)
D1 = 1N4001
D2 = 1N4001
Final Notes:
Circuit is build up arround the LM
or NE556 dual timer. Each timer producing a high or a low tone. The 556
contains two seperate 555 timers so feel free to use the 555's. If you don't
want to fiddle with the reed relay that is fine too. Just put a push on-off
switch between negative and pin 6 of IC1. If you go with the reed relay, mount a
strong magnet underneath the locomotive and mount the reed relay somewhere
between the tracks on a place where you want the horn to be sound. Make sure the
reed relay is positioned in such a way that the magnet is able to close the
contacts. The sound is very realistic. Have fun!
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