How can i display frequency on 7-segments? Homemade RPM-Meter

[Lac]

Hi.
How can I create a rpm-meter for my motorcycle that uses the pulses sent to the coil to display the motors rpm, rather than magnets on the front wheel and a hall effect chip. The idea I have is to connect the base of a transistor to the cable going to the coil, and send +6v through. That way I will, hopefully, get 6V pulse which varies between 10hz-100hz depending on the motor RPM. But the problem is how I can make a LCD-display or maybe easier: 7-segment leds, to display the frequency (RPM). Is there some kind of IC that does the math and converts the frequency into a signal which I can feed directly to the 7-segments? Much like the IC which is used to create digital clocks.
Cheers.
Lac.

 

[k7elp60]

There are IC's that do what you want, but I am sure you will have to do some conditioning of the signal from the points as it may be much higher than the battery voltage and you may have more than one pulse per revolution of the engine. I am sure there are some PIC microcontrollers that will do the job and with proper programming the extra pulses will be taken into effect.

 

[Lac]

The signal is picked up from the wire going into the coil, not the wire going out of it. Also, since it is a two-stroke engine there is only one pulse per revolution. Could you give me the names of the ICs which does what i want please? Thanks.

 

[k7elp60]

What do you estimate the maximum RPM of the engine is? Knowing the maximum rpms will help me recommend an IC for you. I was talking about the input wire to the ignition coil. Because of a collasping magnetic field the
signal on the input can have a higher voltage negative pulse.

 

[Rolf]

Link to simple RPM meter......

The signal is picked up from the wire going into the coil, not the wire going out of it. Also, since it is a two-stroke engine there is only one pulse per revolution. Could you give me the names of the ICs which does what i want please? Thanks.

This looks about as simple as they come:
http://www.josepino.com/pic_projects/index?tachometer2.jpc
Just remember to clamp the input signal to an amplitude that is not damaging to the PIC.

 

[Lac]

What do you estimate the maximum RPM of the engine is? Knowing the maximum rpms will help me recommend an IC for you. I was talking about the input wire to the ignition coil. Because of a collasping magnetic field the
signal on the input can have a higher voltage negative pulse.

The datasheet says 5500r/min