RPM gauge install on B7100 HST

[PoTreeBoy]

This style of sensor is used with and mounted close to a strong magnet you supply with the magnet attached to the rotating member. A small rare earth magnet would be the best choice because you want a very strong magnetic field from as compact a device as reasonable.

You sent me back to YouTube (of course ) for a refresher. There is a type of inductive sensor that contains a permanent magnet and doesn't require external magnet or power. I think that's what HEI ignition and these tachs use. I think it does work better with sharp edges as opposed to rounded ones.

There are also Hall effect sensors that require external power.

If I were in OP's shoes, I'd do some experimenting before I installed one.

 

[RBsingl]

You sent me back to YouTube (of course ) for a refresher. There is a type of inductive sensor that contains a permanent magnet and doesn't require external magnet or power. I think that's what HEI ignition and these tachs use. I think it does work better with sharp edges as opposed to rounded ones.

There are also Hall effect sensors that require external power.

If I were in OP's shoes, I'd do some experimenting before I installed one.

I agree completely about experimenting before install. This sensor and tach combination can be very sensitive to strength of signal from the sensor and any noise on the line. And I suspect there is a fair amount of part to part variance.

I tried one of these style sensors several years ago for a different project and the clearance between the magnet and sensor was about paper thin for reliable operation.

Rodger

 

[PoTreeBoy]

I agree completely about experimenting before install. This sensor and tach combination can be very sensitive to strength of signal from the sensor and any noise on the line. And I suspect there is a fair amount of part to part variance.

I tried one of these style sensors several years ago for a different project and the clearance between the magnet and sensor was about paper thin for reliable operation.

Rodger

I wonder how high the signal level can be before it lets out the magic smoke? I'm wondering if the OP could just hook onto the dynamo's AC output? Maybe a couple of resistors to make a voltage divider?

My OCD just doesn't like a v-belt drive before the tach sensor.

 

[RBsingl]

I was thinking about the same approach. I am not familiar with the characteristics of the dynamo circuit how much the output varies over the operating range along with load and regulator changes.

I would expect the Chinese tach signal circuit to present a high load impedance so that a fairly simple voltage divider could be used with a high value resistor the series element avoiding any loading issues on the dynamo output due to the shunt resistor following the series resistor. But if the tach is sensitive to dynamic range, it might need to be fed with a signal conditioning IC with its own gain control system. With any luck, the tach already has that circuit inside.

Rodger

 

[PoTreeBoy]

I'm thinking that if it'll work over the frequency range advertised, it must not be too picky . I'd wire a high value pot between one of the AC wires and ground, with the wiper to the tach input. Start with it turned down, then turn it up 'til it (hopefully) works across the full RPM range. Then make it permanent.

Have to figure out the multiplier.

 

[lmichael]

Just one

Rodger

Cool. That may be the ticket. I prefer an analogue (dial type) gauge anyway

 

[AOW162435]

Hi fellows- I have a question for you- My 1990? B7100 did not come with an RPM gauge. Has anyone ever added one to their tractor? If so,, how and where did you install it? I would love to have the 2in, dial kind..thax

Bill,
A little late to the party here, but I found your thread after searching about this very topic. I intend to add an analog VDO tach to my '79 B7100 in the future. I did the same on my '03 JD x595 (3-cylinder Yanmar diesel) and it has worked flawlessly for about 6 years:

x595 with VDO tach


Andreas

 

[lmichael]

What is the reason for the extra electronics if, it is a magnetic sensor?

 

[JasonW]

I just installed the Diesel tiny tach on my ZD331 last week. I would have preferred a analog gauge for quick reference but there wasn’t a good/clean way to mount it. The sensor attaches to the fuel line. I pulled the fuel line to sand off the paint, installed the sensor and repainted. The paint drying took longer than the rest of the install.

 

[AOW162435]

What is the reason for the extra electronics if, it is a magnetic sensor?

The sensor is a magnetic pickup that counts the passing teeth on a flywheel or other toothed wheel. It puts out a signal that the Dakota Digital box translates into something that the tach comprehends. Or so I understood it a few years ago.
I'll either figure out a way for the pickup to read the flywheel, or come up with a solution using the forward end of the crank.

Andreas

 

[lmichael]

Oh, I assumed you simply mounted a small magnet to it. Then had the sensor pick the magnets pulse. IDK the whole wanting a tach thing is becoming harder and to the point where I may just have to bite the bullet, buy the Tiny Tach, and adapt it to where my hour meter is. But, I absolutely abhor digital stuff for engines and such. I like needles and analogue readings

 

[TheOldHokie]

Oh, I assumed you simply mounted a small magnet to it. Then had the sensor pick the magnets pulse. IDK the whole wanting a tach thing is becoming harder and to the point where I may just have to bite the bullet, buy the Tiny Tach, and adapt it to where my hour meter is. But, I absolutely abhor digital stuff for engines and such. I like needles and analogue readings

Perhaps a little on the large side and a bit pricey:

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Stewart Warner 82644 Stewart Warner Heavy-Duty Plus Series Tachometers | Summit Racing

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Dan

 

[lmichael]

Yeah, I 'll say pricey.

 

[lmichael]

Been pondering something like this 52mm Pointer Tachometer 4000 RPM Tacho Meter Gauge With RPM Sensor For Car Boat | eBay

 

[TheOldHokie]

Yeah, I 'll say pricey.

This better? My point is you can do what you want.

85MM Diesel Engine Tachometer 0-4000RPM w/LCD Hourmeter+RPM Sensor for Car Boat | eBay

Indicating Range:0~4000RPM. Operation mode: LCD display, stepper motor. Protection grade:IP67 for front side;IP65 for back side.

www.ebay.com

 

[TheOldHokie]

Been pondering something like this 52mm Pointer Tachometer 4000 RPM Tacho Meter Gauge With RPM Sensor For Car Boat | eBay

There ya go. All you need to do is find a way fit it to the tractor.

Dan

 

[lmichael]

There ya go. All you need to do is find a way fit it to the tractor.

Dan

Already have some ideas. Only thing puzzling me now is the mag sensor. Is it made for a single magnet which is picked up once per revolution? Since seeing the other post above now I am not so sure of that

 

[AOW162435]

Been pondering something like this 52mm Pointer Tachometer 4000 RPM Tacho Meter Gauge With RPM Sensor For Car Boat | eBay

That's a low-cost alternative to the solution I cobbled together for my x595. Does it allow you to input number of teeth & also fine tune the actual displayed RPM? I didn't see anything noted in the description.

Andreas

 

[AOW162435]

Already have some ideas. Only thing puzzling me now is the mag sensor. Is it made for a single magnet which is picked up once per revolution? Since seeing the other post above now I am not so sure of that

If it's like my setup, the sensor has a rare earth magnet & coil inside of it. It 'reads' the on/off of flywheel teeth going by.

Andreas

 

[TheOldHokie]

Already have some ideas. Only thing puzzling me now is the mag sensor. Is it made for a single magnet which is picked up once per revolution? Since seeing the other post above now I am not so sure of that

The sensor simply outputs a pulse when the reluctor passes by the tip. The tach is what is configured for the number of pulses per revolution - usually via a dip switch on the back. That is how it counts revolutions per minute. Most of these products expect 60 or so pulses per minute so you need a gear of some sort that acts as the reluctor ring. That is typically the starter ring gear but you could bolt a gear to the crank or alternator pulley and use it if you wanted.

Dan