Fishing Aid

04 This circuit provides audible and visible warning when a fish is nibbling the bait. Although this event is fairly easy to signal with electronic means, the circuit is relatively extensive to ensure that it can be powered from a 9 V battery. The circuit is based on a slotted opto- coupler Type CNY37, and a home made notched wheel. Unfortunately, the cur- rent amplification of slotted opto- couplers is very low (0.02 min.), requir- ing considerable current to be fed through the LED before a usable collec- tor current flows in the phototransistor. To avoid rapidly exhausting the battery, MMV, pulses the LED at about 250 Hz and a duty factor of 0.05. MMV2 detects the presence of these pulses. When a fish pulls at the bait, the notched wheel revolves in the slot, and intermittent pulse bursts are received at the trigger input of MMV2. Green LED Di lights, buzzer Bz sounds, and bistable N3-N4 is set, so that red LED D 2 flashes at a 1.5 Hz rate. Di and the buzzer are turned off when ...