[solved] Looking for an off-the-shelf electronic "counter" to count rotations

[K3mHtH]

Hey everyone,
I have a little jig set up to test the life-span of something I'm making, it rotates about 1 time per second and I'd like to count up to 10M rotations. The power I have available is 3.3V and I'd like the count to remember and continue when the device is turned off.

I'm wondering if there's something Off The Shelf available that I can use for this. Ideally I'd be counting the rotations without contact, something like a hall effect sensor or ultrasonic, etc.

I'm not exactly sure what it's called I'm looking for or where to search,

thanks for your time!

[ledtester]

Maybe search for "pulse counter", e.g.:

https://www.kuebler.com/us/products/evaluation/displays-and-counters/pulse-counters

or "digital counter":

https://www.mcmaster.com/products/digital-counters/

[audiotubes]

Stroboscopes can determine revolution speed, I guess they should also be able to count revolutions.

[Dan123456]

Would an IR transceiver work?

Put a little reflective tape on the shaft and use that to count the turns via an Aurduino / microcontroller 

[brucehoult]

Maybe search for "pulse counter", e.g.:

https://www.kuebler.com/us/products/evaluation/displays-and-counters/pulse-counters

Their stuff costs ~$250!

I see on amazon you can get 20 Hall effect sensors for $8, including shipping. If you want a display locally then a small serial (I2C or SPI) LCD display costs a couple of bucks.

That's few enough pins used that an 8 pin MCU such as an ATTiny85 or CH32V003 could do the job. Both run just as well on 3.3 and 5 V with no external components needed. The AVR has EEPROM that can store the count during power-down, and the WCH has flash that can be used for the same purpose. Neither are spec'd for 10 million rewrites, so you probably want to write the count to non-volatile storage only from time to time. Which means you probably want another input pin to tell you when the power has been switched off, and a capacitor to continue to power the MCU for long enough to save the data without risk of corruption.

[BeBuLamar]

Off the shelf mainly for industiral use and they don't have to sell them cheap but I think this would work as it's operated by a built in battery so it stay on.
https://bigbearinstruments.com/Veeder-Root-C342-Series-Counter?gad_source=1&gclid=CjwKCAiAvoqsBhB9EiwA9XTWGW0_o0bcBvqSJ4p32jYQEKvf--_-J0_EQQue9vjvo2ey9WNbwsRF1RoCBW4QAvD_BwE

[ledtester]

Here's another related thread:

https://www.eevblog.com/forum/beginners/need-a-counter/

[YTusername]

I am not sure why you want to count the rotations without contact, but if this is because you are worried that the wires can't rotate with the "tested" rotating object, then there is a special type of connector for this case. One side of the connector will rotate with the object and the rotation sensor, and the other side will be fixed, providing the wires to external processing. You may also think of having a rotation sensor attached to the object's body and providing rotation information wirelessly.

Gyroscope can provide that information easily, you can develop such a sensor in a few hours. Also if you have a special reason to be an external sensor, then you can use computer vision that can detect a marker on the rotating object. This computer vision has a limitation based on the Camera FPS.

[CatalinaWOW]

Do you need single digit resolution?  Put put the sensor through a divide by eight bit (1024) prescaler and use one of the cheap four digit rotation counters on eBay, Alibaba and everywhere else.  It seems likely that you even gang two of these counters without too much difficulty.

[K3mHtH]

Thanks for the suggestions everyone, although I'm not sure why so many people suggested a complicated DIY approach when I wanted an off-the-shelf solution

Anyways, I picked up one of these: https://www.aliexpress.com/item/1005005578547939.html?spm=a2g0o.order_list.order_list_main.30.73c218027XjVNM

Counter goes up by 1 every time the magnet passes the sensor, so also satisfies the contactless requirement. AA powered as well so it remembers the count even after the testing apparatus is turned off. Might be helpful for others looking for something similar.

[brucehoult]

Thanks for the suggestions everyone, although I'm not sure why so many people suggested a complicated DIY approach when I wanted an off-the-shelf solution

We didn't know any off the shelf solution that met your spec of a 10M count?

Hard to know whether "off the shelf" (wondering) or "10M count" (would like) was the more important requirement and until just now you had not given any clarification.

The item you linked to doesn't meet the count spec.

[CatalinaWOW]

Thanks for the suggestions everyone, although I'm not sure why so many people suggested a complicated DIY approach when I wanted an off-the-shelf solution

Anyways, I picked up one of these: https://www.aliexpress.com/item/1005005578547939.html?spm=a2g0o.order_list.order_list_main.30.73c218027XjVNM

Counter goes up by 1 every time the magnet passes the sensor, so also satisfies the contactless requirement. AA powered as well so it remembers the count even after the testing apparatus is turned off. Might be helpful for others looking for something similar.

You realize that the selected counter at 6 digits doesn't meet your 10 million count requirement don't you?

[K3mHtH]

You realize that the selected counter at 6 digits doesn't meet your 10 million count requirement don't you?

It counts up to 1 million, so marking a piece of paper 10 times as it rolls-over is still a lot easier than DIYing a solution from scratch.

[brucehoult]

You realize that the selected counter at 6 digits doesn't meet your 10 million count requirement don't you?

It counts up to 1 million, so marking a piece of paper 10 times as it rolls-over is still a lot easier than DIYing a solution from scratch.

Perhaps that was already the plan with the 10M count. We weren't told the RPM so that could be the difference between checking it for rollover once a day vs having to check it every two hours 24/7.  Or once a week vs once a day. Or once a year vs every month.

[CatalinaWOW]

You realize that the selected counter at 6 digits doesn't meet your 10 million count requirement don't you?

It counts up to 1 million, so marking a piece of paper 10 times as it rolls-over is still a lot easier than DIYing a solution from scratch.

I am actually glad you found a solution that you like.  And suggest that you check to see if the counter you purchased has a rollover electrical output (not terribly unlikely).  If so you can plug that into the input of a second counter to add a rather large number of zeros to the total.  Yes, it is DIY, but in the really simple range, and has the advantage that it doesn't require that you not be on vacation or ill or anything else which might screw up your count. 

As a belt and suspenders approach I would recommend recording the counter output at regular intervals so that if something unexpected happens (battery failure, someone disconnects your probe or other catastrophe) you can reasonably estimate what the count was, and hopefully convince whoever you have to convince that there is no need to start over.  The interval will depend on a number of things, the rotation speed, how often you or someone else will be available and how much evidence you think you will need for the post failure sales job.