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Does Any body need a timing light circuit? Answered

I was thinking that i should post one here but thats if anybody actually needs it.

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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!

I'm thinking that I can use a 555 to change the frequency of the LED but how would I know exactly what frequency it is flashing at?

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

I don't need a pickup. I want to adjust the frequency of an led untill a fan 'stands still" then read the freq or rpm of the 555.

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 : /

the output of the 555 will be a variable freq square wave. Is there an easy way to make it display onto a 7 segment display?

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

I need one. I would like to make an led timing light that I can use to determine the frequency of rotating objects.