which electronic signal at rpm output?

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Little.desperado

Seaman
Joined
Sep 2, 2003
Messages
52
Hi,<br /><br />I've got a 1989 30hp Evinrude with a Evinrude remote control.<br />My dealer said i can connect a tachometer to the output of my remote control.<br />As the original Evinrude tachometer is quite expensive here in Germany(about 300 Euro), i asked my dad to build a digital one.<br />T<br />herefor we need the output signal.<br />So i hope anybody can tell me what kind of signal that exactly is.<br /><br />Thank u very much!
 
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Paul Moir

Admiral
Joined
Nov 5, 2002
Messages
6,847
Re: which electronic signal at rpm output?

The tach signal is just a rectified stator signal, so you get about a 14.5v sinusoid shaped pulse train. The two cylinder version should produce five pulses per rotation of the engine and the three cylinder 30hp should produce 6 pulses per rotation. Best bet is to count the number of poles on the stator and divide by 2.<br /><br />If the battery gets disconnected for whatever reason the voltage can shoot up quite high. You'll want to protect the input with a resistor & zener or some such device.
 
L

Little.desperado

Seaman
Joined
Sep 2, 2003
Messages
52
Re: which electronic signal at rpm output?

Thank You very very much for your helpful reply!<br />I'll tell my dad and hope he can build some good tachometer!
 
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byacey

Chief Petty Officer
Joined
Jul 20, 2005
Messages
443
Re: which electronic signal at rpm output?

This assumes the motor has a charging system. If not, and your father has experience with electronics, build a counter that will count the pulses between the points connection and engine ground. For a two cylinder, there will be 2 pulses per revolution if you count and add the two points signals together, or just count off 1 set of points, and you have 1 pulse per revolution.
 
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