RPM Alternator Pulse count signal conversion - Alternator Pole Count

[rogerthebodger]

The convertor you have shown should work as I have found from the Starter ring part number followed by an Ebay search this is a 159 teeth starter ring.

This results in a max hz at 3000 RPM of 7,950 hz. The actual engine max speed is 2,700.

I wil need to knock up some simple threaded adaptors for the mount holes which are 3/4 - 18 UNF, with the probe M12. I think I can also get to the tacho probe mount holes on both engines OK. I assume ~ 2mm clearance from the teeth is sufficient.

You would need to adjust the tooth sensor gap so to avoid and interaction with the next tooth on the gear ring dependent on the tooth pitch.

You only need a clearance hole for the sensor as the gap would be adjusted with the 2 locking nuts on the sensor.

 

[vas]

fwiw, I installed such a sensor on the crank pulley of my yanmar generator. Well, the magnet on the pulley, the sensor secured with a custom bracket.
just multiply with 60 to get rpm obvs. However signal wasn't that clean, again needed software routines to sort it. Fingers crossed it will work on your setup.

 

[rogerthebodger]

fwiw, I installed such a sensor on the crank pulley of my yanmar generator. Well, the magnet on the pulley, the sensor secured with a custom bracket.
just multiply with 60 to get rpm obvs. However signal wasn't that clean, again needed software routines to sort it. Fingers crossed it will work on your setup.

Or just fit a denouncing circuit to clean up the signal.

A simple R C circuit could be used of again=in 555 timer or a 47LS14 or CMOS 4047.

 

[superheat6k]

Or just fit a denouncing circuit to clean up the signal.

A simple R C circuit could be used of again=in 555 timer or a 47LS14 or CMOS 4047.

The access hole is blind, with access from the outside only (I am not taking the engine out just to install this thing !) , but is threaded 3/4" -18 UNF, so a threaded adaptor to accommodate the M12 sensor will be necessary. I will screw it in until it gently contacts the teeth then back it off 1.25 turns which for M12 = 2.2mm. I can then adjust it a small amount as necessary. I will bar the engine by hand a full revolution to make sure nothing fouls it before I spin the starter.

I will run the cable in decent quality shielded with the shield grounded, so that should sort out any cable noise.

 

[JohnGC]

The access hole is blind, with access from the outside only (I am not taking the engine out just to install this thing !) , but is threaded 3/4" -18 UNF, so a threaded adaptor to accommodate the M12 sensor will be necessary. I will screw it in until it gently contacts the teeth then back it off 1.25 turns which for M12 = 2.2mm. I can then adjust it a small amount as necessary. I will bar the engine by hand a full revolution to make sure nothing fouls it before I spin the starter.

I will run the cable in decent quality shielded with the shield grounded, so that should sort out any cable noise.

The datasheet implies a sensor distance of 2mm although it doesn't specify if this is optimal, minimum or maximum. I don't doubt I'm about to teach my father's mother to suck avian ovoids but; add some thread lock once you have it set-up, you don't want it coming lose such that the gap reduces to zero or less!

 

[vas]

fwiw, on a magnet, mine wasn't happy at more than 2mm

 

[superheat6k]

The datasheet implies a sensor distance of 2mm although it doesn't specify if this is optimal, minimum or maximum. I don't doubt I'm about to teach my father's mother to suck avian ovoids but; add some thread lock once you have it set-up, you don't want it coming lose such that the gap reduces to zero or less!

Oh it won't be coming loose !

A self created engine removal as a side effect of having a nice tacho input into my protection system is not part of my plan !

The sensor does look quite powerful at sensing, but we wil see.

I am hoping I have a 3/4 UNF die, otherwise looks like I will be practising some thread cutting this weekend, although I might have some old bolts or studs of this thread in one of my tins of stuff never to be thrown out.