Installing a digital tachometer

[whydontu]

Bizarreness.

My tach bounces around a bit, but just the odd hiccup on maybe one out of every twenty display updates.

The magnet I’m using is smaller and thinner than yours.

Upper row 550 to 1620 mirrors my results. Your numbers are off less than 10%, mine are off 14%. Odd that they are not consistent.

Slow speed error makes me go wtf? No scenario I can think of would allow 550/600 but then also result in 350/760

Wild-ass guess - the power supply you have is a switching supply. Try running the tach from a 12v battery. Maybe there‘s interference from the switch mode dc output power supply.

 

[combustable herbage]

Bill I had the similar issues with mine jumping around and it was the power supply had too much noise, when I ran it using a 9v battery it was solid. I tried a different power supply with better results, but I took apart because I moved my lathe to its new stand and I haven't rewired it back up yet. The other thing to check for is if there is an led at the orange end of the sensor in picture one on mine at least when its running slow you can see a blinking led there that can also be an indication that the sensor is working.
From the experimenting i did I thought the magnet was fairly forgiving but I have quite a strong magnet.

 

[Dusty]

I love the install. Very slick and professional looking.

I re-read your post. You talked about the magnet orientation, but isn't obvious to me if you actually tried the magnet upside down.

Regardless, here is a whacky suggestion - try a fatter magnet. At least as big in diameter as the sensor.

Also, many magnetic sensors are sensitive to the gap between the sensor nose and the magnet.

That's all I got.

@Susquatch thanks for you feedback and kind words. Oh yes I tried that magnet every way but loose (from an old movie). LOL

Tomorrow I'll readjust the clearance between the sensor nose and magnet, instructions say 2-3 mm max. Shall also retry the magnet that came with the kit. Has to be something simple trick is to locate it.

 

[Dusty]

Bizarreness.

My tach bounces around a bit, but just the odd hiccup on maybe one out of every twenty display updates.

The magnet I’m using is smaller and thinner than yours.

Upper row 550 to 1620 mirrors my results. Your numbers are off less than 10%, mine are off 14%. Odd that they are not consistent.

Slow speed error makes me go wtf? No scenario I can think of would allow 550/600 but then also result in 350/760

Wild-ass guess - the power supply you have is a switching supply. Try running the tach from a 12v battery. Maybe there‘s interference from the switch mode dc output power supply.

Interesting information, so then I'm not alone and the only one with out of sink fluctuations. Read my post #63 to Susquatch.

Thinner and larger diameter magnet is a consideration for sure. I hate problems like this in my tender years. LOL

Power supply may very well be the culprit as it came from a chaps save stuff box at a local computer shop.

I'll be very happy if I can get the dang thing to settle down some. On the flip side one has to keep in mind where my Ching Chong kit came from, not exactly top of the line stuff. I have another power supply, must check that out to see if that will solve some of my trouble.

Some days I ask myself how in hell did Billy ever get into this, then I answer myself because its so much fun and for the challenge. LOL

 

[Susquatch]

Some days I ask myself how in hell did Billy ever get into this, then I answer myself because its so much fun and for the challenge. LOL

Wise words. Wisdom is mostly a property of age.

I remember a long long long time ago complaining about a really tough assignment I was given. "That's impossible!" says I, to which the old senior fellow looks at me and says "Hey, if it were easy, we wouldn't need you! "........ With those wise words, he put a whole new perspective on things......

Yup, have fun Billy! This problem too will be simple when solved.

X2 - for the power supply!

 

[ShawnR]

@Dusty I will throw a few things your way. Forgive me if they have been already suggested

Look into the tach box and see if you can see any switches or pins. Sometimes the pins are used for configuration by a shorting connector. As @combustable herbage suggested, a battery will provide a solid DC source, which may point you to, or away from, a power supply issue. A capacitor across your power supply might filter enough to make it more reliable.

Are you able to retrieve your order info and post a link to the actual tach you bought? That may help. A few of us have used similar ones but you might have a slightly different one so knowing that might help us help you.

One last suggestion is... don't be afraid to back off your air gap a bit. Just cause they say 2-3 mm max...that was done in their test setup with their test magnet, probably not any of your actual components. Reasoning says closer for a magnetic pickup should be better but I had issues with my optical pickup previously and I found that backing it off made it way more reliable. I know that is slightly different (optics vs magnets) but nothing to lose by backing the sensor away a couple mm at a time to try. The fact that it is picking some up means the system is working.

There are some more tests we can do to determine if the sensor or tach is at fault but you have a bit to work on for now.

Good luck!

 

[6.5 Fan]

Jeeez Bill, if you need a different 12volt power supply just hook it up to that pristine Buick you have sitting there.

 

[Dusty]

Jeeez Bill, if you need a different 12volt power supply just hook it up to that pristine Buick you have sitting there.

@6.5 Fan as much as I would like to do that I can't because my vehicle isn't a Buick. LOL

Yes it's a 2017 XT5 Caddy with only 10,000 clicks on it, haven't been able to drive it for over three years due to my multiple right knee surgeries.

Read my post #69 to Shawn.

 

[Dusty]

@Dusty I will throw a few things your way. Forgive me if they have been already suggested

Look into the tach box and see if you can see any switches or pins. Sometimes the pins are used for configuration by a shorting connector. As @combustable herbage suggested, a battery will provide a solid DC source, which may point you to, or away from, a power supply issue. A capacitor across your power supply might filter enough to make it more reliable.

Are you able to retrieve your order info and post a link to the actual tach you bought? That may help. A few of us have used similar ones but you might have a slightly different one so knowing that might help us help you.

One last suggestion is... don't be afraid to back off your air gap a bit. Just cause they say 2-3 mm max...that was done in their test setup with their test magnet, probably not any of your actual components. Reasoning says closer for a magnetic pickup should be better but I had issues with my optical pickup previously and I found that backing it off made it way more reliable. I know that is slightly different (optics vs magnets) but nothing to lose by backing the sensor away a couple mm at a time to try. The fact that it is picking some up means the system is working.

There are some more tests we can do to determine if the sensor or tach is at fault but you have a bit to work on for now.

Good luck!

@ShawnR all good suggestions Shawn, was up early out in my shop tinkering around like adjusting the gap and changing magnets unfortunately without improving tachometer issues. Unfortunately I do not have the sales invoice from Banggood as I bought the digital kits well over two years ago.

Our eldest son in Regina is a wizard with electronics, so should I remove my system he has agreed to work out the bugs on his well equipped work bench, now that's an offer I can't refuse.

What can I say, wait and see what bubbles to the top.

 

[Dusty]

My digital tachometer instructions on power supply use. Power supply: 8-15VDC, Max current: 300mA, Response frequency: 100HZ.

Power supply I was using, 120V~60HZ, DC/CC12V--- 500mA.

My conclusion is 500 mA did not auto adjust being far too much for the job. When I say that I'm only taking a wild guess?

Checking amazon.ca and their power supply reviews I come up with this one which I believe would be stable for the job.

This post is for all the DIY electricians by picking your brain so to speak. My only concern is their add makes no mention of maximum mA's or that it's auto adjusting? Sure don't want to fry another RPM meter which I believe happened with my first one by using a 500mA power supply.

Assistance please, lost in the numbers game, open to suggestions as always.

https://www.amazon.ca/ALITOVE-Universal-Adjustable-Household-Electronics/dp/B07QX4J9VY/ref=sr_1_20?crid=V5SUWTW1N6RL&keywords=supernight+ac+-dc+converters&qid=1654045166&s=electronics&sprefix=supernight+ac+-dc+converters,electronics,132&sr=1-20&th=1

Perhaps this one is a better choice?

https://www.amazon.ca/dp/B07Y1V9B7N/ref=syn_sd_onsite_desktop_68?psc=1&pd_rd_plhdr=t&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEyTDFHUkU5TlBOTlkmZW5jcnlwdGVkSWQ9QTA2MjI2MzFFNE9JU1VOT05UVjImZW5jcnlwdGVkQWRJZD1BMDA5NTcwNFlPVzZKM05LMkswNSZ3aWRnZXROYW1lPXNkX29uc2l0ZV9kZXNrdG9wJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==#customerReviews

 

[DPittman]

My digital tachometer instructions on power supply use. Power supply: 8-15VDC, Max current: 300mA, Response frequency: 100HZ.

Power supply I was using, 120V~60HZ, DC/CC12V--- 500mA.

My conclusion is 500 mA did not auto adjust being far too much for the job. When I say that I'm only taking a wild guess?

Checking amazon.ca and their power supply reviews I come up with this one which I believe would be stable for the job.

This post is for all the DIY electricians by picking your brain so to speak. My only concern is their add makes no mention of maximum mA's or that it's auto adjusting? Sure don't want to fry another RPM meter which I believe happened with my first one by using a 500mA power supply.

Assistance please, lost in the numbers game, open to suggestions as always.

https://www.amazon.ca/ALITOVE-Universal-Adjustable-Household-Electronics/dp/B07QX4J9VY/ref=sr_1_20?crid=V5SUWTW1N6RL&keywords=supernight+ac+-dc+converters&qid=1654045166&s=electronics&sprefix=supernight+ac+-dc+converters,electronics,132&sr=1-20&th=1

As I understand, an electronic device generally won't draw more current than what it needs just because it's available. So I would think your 500ma supply should not hurt. I'm no expert so take that advice for what it's worth.

 

[Susquatch]

As I understand, an electronic device generally won't draw more current than what it needs just because it's available. So I would think your 500ma supply should not hurt. I'm no expert so take that advice for what it's worth.

You are correct.

The current rating only comes into play when the supply voltage gets dirty because it needs more or less current draw. Generally speaking the primary issue is usually insufficient current and very rarely too much.

Assuming the problem is the power supply (which is only one possibility among many) I'm guessing the power supply is too dirty and has a lot of noise on the line feeding the tach. Lots of devices can't handle noise on the line. But cheap supplies are usually quite dirty. On the other hand, it doesn't make sense to use a 200 dollar supply to power a 10 dollar device.

You can best check If the problem is the power supply by trying it with a car battery. They are virtually noise free and will provide plenty of oomph for this job. Looking at the tach specs lead me to believe that it was designed to be used with a car electrical system.

 

[Dusty]

You are correct.

The current rating only comes into play when the supply voltage gets dirty because it needs more or less current draw. Generally speaking the primary issue is usually insufficient current and very rarely too much.

Assuming the problem is the power supply (which is only one possibility among many) I'm guessing the power supply is too dirty and has a lot of noise on the line feeding the tach. Lots of devices can't handle noise on the line. But cheap supplies are usually quite dirty. On the other hand, it doesn't make sense to use a 200 dollar supply to power a 10 dollar device.

You can best check If the problem is the power supply by trying it with a car battery. They are virtually noise free and will provide plenty of oomph for this job. Looking at the tach specs lead me to believe that it was designed to be used with a car electrical system.

As mention earlier in post #64 said power supply came from a rummage box of sorts at a local computer shop. Rather doubt it was used with a vehicle electrical system. On the flip side my garage/shop has florescent lighting plus ceiling fan hanging from the vaulted ceiling, making for loads of noise in my shop electrical system. Our home has vaulted ceilings throughout which continues out to our attached garage.

Presently my kit is removed from my lathe waiting for our son in Regina to pick it up this coming Sunday, family birthday party for our only great-grandson's first birthday. Should be a ball watching him eat cake. LOL

 

[Dusty]

@Susquatch tomorrow when I'm fresh in mind I will jury rig my digital tachometer to my vehicle battery, that makes sense.

Shall advise accordingly!

 

[ShawnR]

I am doubting your issue is power supply, but I do agree that it is best to rule it out first. The battery trial is the best to do, imho. Any lawn tractor batteries around that you could hook some wires from? A 9 volt will run it in theory but at 300 ma, it may drop below a fair assessment value.

Edit.....oops....looks like we were typing at the same time. Looking forward to hearing back

 

[Susquatch]

As mention earlier in post #64 said power supply came from a rummage box of sorts at a local computer shop. Rather doubt it was used with a vehicle electrical system.

Not the power supply. The tach.

 

[Dusty]

Not the power supply. The tach.

Yes the tach, don't believe I said the power supply in my post #74.

 

[Susquatch]

Yes the tach, don't believe I said the power supply in my post #74.

OK.... So in my post 72 I said

Looking at the tach specs lead me to believe that it was designed to be used with a car electrical system.

In your post 73 you said:

As mention earlier in post #64 said power supply came from a rummage box of sorts at a local computer shop. Rather doubt it was used with a vehicle electrical system.

In my reply #76, I said

Not the power supply. The tach.

I meant I had been referring to the tach not the power supply when I said it was prolly automotive.

Hope that clears our confusion up. Too much fun! Isn't it great getting old! But it sure beats the crap out of the alternative!

 

[Dusty]

OK.... So in my post 72 I said



In your post 73 you said:



In my reply #76, I said



I meant I had been referring to the tach not the power supply when I said it was prolly automotive.

Hope that clears our confusion up. Too much fun! Isn't it great getting old! But it sure beats the crap out of the alternative!

Getting old is not for sissies my friend.

 

[Dusty]

@Susquatch my update to my digital tach dilemma. So I connect the 12 volt digital tach set up to my vehicle battery, although the sensor light came on there was no sign of life from the digital display even with passing the magnet by the sensor. Was working before I removed the kit from my lathe. Now I'm completely mystified with that. Shall pass the challenge to our son in Regina tomorrow. Meanwhile a new 110/120v - 12v converter is on it's way from amazon, should be delivered Monday.

Lost somewhere between + and - although always grounded. LOL