IR without EDU '04 Robot

[Dale(294engr]]

Construct a two 555 timer chip circuit (one 7555 CMOS dual timer pkg)

(see ICM 7555 data sheets for astable variable duty & 50-50 application info)

to drive the IR Beacon (see my previous post)
One timer for 100Hz 5% duty (or 95%) driving
2nd timer at 50-50 duty, 40kHz, driving FRRC MOSFET & IR LEDS.
(can add a pot to vary 40lHz +-5Khz to test 4840 rcvr sensivity at distance)

suggest 2 IR diode series strings 16 ohms each,
driven by FRC logic level MOSFET, 4.5-5v battery supply

or one string of 4 for use with 7.2 (to 8v rechargable)
(use IR LED Vfwd=1.34v for calcs Rlimit=V[supply-Vled(s)]/I,
I = 100-200mApk)

note batteries will last much longer with this CMOS driver
and low average power of series LED strings than
EDU (drqws ~.1A constant) on 800mAHr niCads
driving 4 parallel strings.

IR LED current limit resistors can be tailored
for various optical output powers
~100 mA to 200 mA pk per LED or more
(spec sheet up to 1A but much care/skill/knowledge req'd at high current)

regards, Dale 294