There is always a need. It may not be today....... but there will be a need and and you have the potential of pleasing a person at a later point in time. Also, refer to the "kiteman law"...... oh, the irony!

thats a good question, you can manually set the 555 timer to a specific frequency by using a formula and it can be found here http://www.daycounter.com/Calculators/NE555-Calculator.phtml and if the frequency is constantly being varied then u'll have to use a frequency counter. i did make a prototype of the timing light but i have a issue with it.it works but not on the plug wire as i expected. if i place it closer to the distributor (device on a car ) it flashes but i know it is picking up all the spark signals and not 1 as its suppose to

ok well not sure how it will work but you could buy a frequency counter or make a type of tachmeter. Well i was looking for something simpler didnt find any heres the lm331. http://www.ti.com/lit/ds/symlink/lm231.pdf ON page 11 there should be a circuit showing how you can get a voltage from a frequency. Theres 1 limitation of the circuit you can only go up to 10khz, you could google Frequency to Voltage Converters and find a circuit which suits your needs. The advantage is you can connect your 555 timer circuit and i assume you know how to do this to the input of this circuit. You vary your 555 timer using a potentiometer it until you can see that the led on ur fan is still. At the same time the circuit will produce a voltage. Use multimeter to read it. Record the volatge then place it into the formula below ( this formula will only work for the circuit i introduced you to any other circuit the formula changes) Frequency In = Voltage Out x 2.09 x RL/RS x (Rt x Ct). Hope i remember my maths correctly. Hope it helps : /

you could try purchasing something like this, http://www.amazon.com/SparkFun-Frequency-Counter-Kit/dp/B004G2DFYG/ref=sr_1_3?ie=UTF8&qid=1342472497&sr=8-3&keywords=frequency+counter i dont this the 7 segment thing is easy

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and if the frequency is constantly being varied then u'll have to use a frequency counter. i did make a prototype of the timing light but i have a issue with it.it works but not on the plug wire as i expected. if i place it closer to the distributor (device on a car ) it flashes but i know it is picking up all the spark signals and not 1 as its suppose to

ON page 11 there should be a circuit showing how you can get a voltage from a frequency. Theres 1 limitation of the circuit you can only go up to 10khz, you could google Frequency to Voltage Converters and find a circuit which suits your needs. The advantage is you can connect your 555 timer circuit and i assume you know how to do this to the input of this circuit. You vary your 555 timer using a potentiometer it until you can see that the led on ur fan is still. At the same time the circuit will produce a voltage. Use multimeter to read it. Record the volatge then place it into the formula below ( this formula will only work for the circuit i introduced you to any other circuit the formula changes)

Frequency In = Voltage Out x 2.09 x RL/RS x (Rt x Ct). Hope i remember my maths correctly. Hope it helps : /

http://www.amazon.com/SparkFun-Frequency-Counter-Kit/dp/B004G2DFYG/ref=sr_1_3?ie=UTF8&qid=1342472497&sr=8-3&keywords=frequency+counter

i dont this the 7 segment thing is easy

As onrust says, you must remember The Law.