@sicastor. see actually my problem statement goes like this. There will be a conveyor belt rotating at 10 rpm speed. i wil have 3 coins of diameter 2,4 and 6 cms and their values are 1,2 and 3 respectively. now these coins of various numbers wil be placed in the belt. i got to show the value of these coins in the 7 segment display without using a microcontroller and 555 timer. these coins are made of wood. now i got two ideas first is i wil use a schmitt trigger for generating a square wave and use pulse width modulation to generate 40 khz and in the receiver side i wil have tsop receiver. the next idea is to use a laser and ldr. which wil be the best?the next step wat i wil do is give this output as clock to the flipflops(i wil realise a counter using flipflops) and finally give it to 7 segment.
sorry if my way of asking is bad. i don wanna get the whole solution as am a beginner am stuck at various points..also thanks for your advice.