O/T circuit board mounted speed sensor that is low cost

[Garwood]

I'd like to add an RPM sensor to a simple Raspberry Pi Pico powered motor controller. I'd like to use a notch or teeth in a steel motor coupling and have a board mounted sensor pick up on that notch to read reliably through 7000+ RPM.

Like what an ABS wheel sensor does or a crank or cam sensor in an engine, only I'm looking for something that I can surface mount directly on a board. I don't want to attach any magnets. Sensor can be 5V or 12/14V. Accuracy is not critical. Low cost and in stock/available are the primary requirements. Whatever the output signal is my electronics guy can make it work.

Any suggestions? Even just a brand name or correct nomenclature for what I need?

Thanks!

 

[Bill D]

Hall effect sensor.
Bill D

 

[Straightedge]

Hall effect sensor.
Bill D

Good answer. Also, see "optical tachometer."

 

[CarlBoyd]

Hall effect sensor requires magnetic field

Hall effect sensor.
Bill D

OP said "I don't want to attach any magnets"

Sounds like optical is the way to go.

CarlBoyd

 

[Garwood]

Optical gets dirty and fails. I didn't mention it, but I don't want optical because it isn't a sealed environment.

I think what I'm needing is an inductive speed sensor- An inductor wrapped around a magnet that will generate a voltage or sine wave passing over a notched or tooth form on a shaft.

 

[eKretz]

Yep, inductive. Should read gear teeth just fine. Often easy to find under "proximity sensor."

 

[Archer120x]

One of the allegro ATS sensors will have the back bias magnet built in. I don't know if they have anything surface mount. Its been a while since I have done sensor design.

 

[Pete Deal]

Magnetic pickup. They may have some with a digital output. Generally it's just an ac signal that you need to message some to get into a digital pulse. If you use a 60 tooth gear the frequency output is the same as the RPM.

Industrial VRS | Honeywell

http://www.farnell.com/datasheets/2058061.pdf

 

[FTF Engineering]

Variable reluctance sensor.

Inductor wrapped around a magnet and the change in the magnetic field (that occurs when you pass something magnetic in close proximity) generates a signal.

 

[memphisjed]

credit to pico-systems. Reads the teeth of gears.

 

[corednc]

I think this might be what you are looking for. Most of it is just PCB layout and a simple sensing target of your choice. The reference board gives you a clearer idea of what is required.

AS5715R Inductive Motor Control Position Sensor | ams

Octopart shows there are about 11K in stock right now, split across two packages and the TSSOP is not too bad at approx $3 per 1K.

 

[Archer120x]

I think this might be what you are looking for. Most of it is just PCB layout and a simple sensing target of your choice. The reference board gives you a clearer idea of what is required.

AS5715R Inductive Motor Control Position Sensor | ams

Octopart shows there are about 11K in stock right now, split across two packages and the TSSOP is not too bad at approx $3 per 1K.

He doesn't want external magnet though.

 

[Archer120x]

Magnetic pickup. They may have some with a digital output. Generally it's just an ac signal that you need to message some to get into a digital pulse. If you use a 60 tooth gear the frequency output is the same as the RPM.

Industrial VRS | Honeywell

http://www.farnell.com/datasheets/2058061.pdf

Careful, VR sensors are not good at low rpm. The signal amplitude is proportional to speed.

 

[Archer120x]

credit to pico-systems. Reads the teeth of gears.

Yes, this one is a possible choice. Not cheap though.

Memphis, not sure why pico systems gets credit for an old allegro camshaft sensor?

 

[corednc]

He doesn't want external magnet though.

Please take another look. It is not an external magnet, there are no "magnets" involved. It is a simple metal disk that can be stamped out and connected to the rotating shaft.

 

[Garwood]

It isn't that picky. Also not hard to enclose or even totally seal. Or purchase already sealed.

Among the 'experimental' goods in the Hell box:

- an optical encoder wheel from a welder wire-feed. ISTR it was nine bucks?

- two each of two types of one meter long stainless-flex armoured fibre optic cable with right-angle prisms at the tip.

- Hall effect sensors

- Non-Hall mag prox sensors.

- 3 or maybe 4 now? different IC's that convert pule-train or variable-frequency sine wave to Voltage level, Varying Voltage level to pulse train/frequency, one. the other, or even both.

The most useful at the end of the day are Servo-Tek tachogenerators. Anywhere from $20 used to still well-under $400 brand-new and made in USA.

Analog @ "n" Volts per 1000 RPM were what my goods need (DC drives.

You'll want pulse trains?

Old stuff. Tons and tons of it, any type you can imagine, is all over surplus channels or not as expensive as all that, even brand-new.

You can do this... and in any of many ways.

Optical will not work for what I'm doing. I can guarantee it will get dirty and fail in short time. I don't want that to happen

 

[Garwood]

They don't give a damn if the OUTSIDE gets dirty.

Industrial encoders absolute | Baumer USA

What did you think "hermetically sealed" meant?

???

How does a shaft encoder read notches on a motor coupling, mount to a circuit board or cost less than a few dollars?

 

[Garwood]

Same answer as lust - at great distance - for certain lovely ladies.

Remain nought but a dream.

That also keeps stuff from getting dirty.

That was too easy. Got another question?



BTW.. Why fixate on the coupling when the motor and shaft exist?

Step back from the tree. Look at the rest of the forest.

Hacker's Second Law Applies:

There is very little truly 'new' in the Universe.
When faced with a challenge, Job One is to FIRST ascertain how the last successful entity met it.
Only THEN whether it requires improvement or only adaptation.


It has saved Hacker a lot of time. And made a lot of money for his employers.

The motor and shaft are beyond my scope. I manufacture the motor coupling and motor mount with integrated controller. Consumer can use any motor from a myriad of options to power their contraption.

 

[Archer120x]

Please take another look. It is not an external magnet, there are no "magnets" involved. It is a simple metal disk that can be stamped out and connected to the rotating shaft.

Ah, looks like it was released after I got out of magnetic sensor design. I like it, uses concepts from lvdt sensors.

 

[Garwood]

So buy what you need from the established masters at THEIR game. Integrate it. CHARGE FOR IT. Sealed hollow ring sensor, for example.

Or do something more profitable with your time if the market ain't there to pay a decent price.

China exists. And not-only. Nobody small survives in the "we are cheaper than" game of diminishing returns.

Go for the premium goods.

Otherwise, "The American Disease" will do you in whilst you race for the bottom, starving.

Where the fuck do you get this nonsense? Not even the tiniest clue as to what the fuck I'm doing and you think I'm racing to the bottom?

Jesus Christ.

Using the wrong sensor for the application, a fucking encoder to roughly sense shaft revolutions, a sensor that costs ten or twenty times what the appropriate sensor should cost is terrible engineering. It's terrible advice on your part. Just plain stupid.

So go ahead, come back with some other poorly conceived solution to a problem I don't have.