INFO WANTED on (Tachometer for under $25 dollars)

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oldgascar

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Aboout a week or so ago, I read with excitement, a posting about setting up a tachometer on a lathe etc. for under 25 dollars.
The original post and and others adding to it seemed to have disappeared.(wierd)
I was either smart enough or lucky enough to have printed out the ebay listing, so I have that info to make the tachometer purchhase. (no optical sensor included with the tach)

But now I am looking for the info on the actual sensor whhich was was used by the original poster, or if someone knows if another will work. I think I have an answer , but I would liike to see any of the orig. post. I know one group member, I think he is from Australia (spelling ?) anyway, his name is Martin and he wrote about his setup & I beleive he even had posted photos of the sensor setup on his belt driven bench lathe.
So, Martin , if you see this ciould you re post your info or send mme a privatee email ?

Thanks,

Bob Ferry
 
The sensor was from Littlemachineshop.com. I will see if I can find it for you.
Found my copy in the files.

Quote:
I posed a question last week concerning installing a tachometer on my HF 7x10 lathe.

I have it built and thought I would post a thread showing what I did.
I can't show you what the installation looks like because I don't have my lathe assembled, so the tachometer isn't on the machine yet.
I did put the interrupter wheel on my ShopFox 6" lathe (Sieg C1) to test it and it worked great, but I had to hold the sensor in place.

I got the tachometer unit for $10 here:

http://www.ebay.com/itm/280938832325...84.m1439.l2649

Of course, since I bought mine a couple of weeks ago, it has gone up to $11.49.
It's still a good deal.

I bought the sensor harness for $10.51 here:

http://www.littlemachineshop.com/pro...1945&category=

These sensors are also available in several different styles, including some that are reflective instead of slotted, on eBay for as little as $1.50. Search for opto interrupter. I bought mine from LMS because it included the bracket.

I also bought the interrupter wheel from LMS for $5.95 here:

http://www.littlemachineshop.com/pro...1946&category=

None of these parts are absolutely necessary, except for some type of sensor. They just made the build easier for me.
If I had been out to save money, I would've just bought the sensor and fabricated everything else. The tachometer is programmable, so you can use whatever number of slots that you wish, including just one. You can also use the reflective type sensor which would require the use of small pieces of reflective tape, if you don't want to use an interrupter wheel.

I also found an old 12 volt wall transformer to use as a power supply.

After I got the parts together, I came up with the schematic.


tachometer Input.pdf. (PDF DOES NOT WORK SORRY)

The box marked "Original Circuit" is the circuit in the harness I bought from LMS except I had to change the resistors.
R1 is to bias the detector. R2 is to bias the LED since I changed the power supply to 12 volts.
The rest of the circuit is an amplifier to increase the current for input into the tachometer.
I had to play around with the resistor values. I did current calculations and the values weren't quite right, so I had to adjust the values. I was able to get the tachometer to work without the additional amplifier (just using the original circuit) but the current was near the limit of the detector, so I didn't know if it would last for extended run times.

Below is the amplifier circuit I built.


If you look at the picture, you will see an LED that is not in the circuit.
I put it in adjacent to R5, between tachometer pin 1 and pin 5 connections.
It is there as a test display to make sure the circuit is working.

It is a very simple circuit. It only has three resistors and a transistor.

Once I get my lathe assembled, I plan on installing the tachometer inside the motor control circuit box.I believe there is room right under the switches and speed control. Once I get to the permanent installation, I'll cut the empty space from the board. It's going to be a tight fit.

If you fabricate your own interrupter wheel or use a reflector sensor, I think it would be possible to build the whole thing for under $20.
End Quote:




Pierre
 
The sensor is a reflective sensor only. I will not be using a wheel to pass thru a sensor head. I want yo use reflective tape. I will try to contact LMS to see if they have available a sensor for reflective tape.
 
Martin listed Omron EE-SPY as his sensor.
Pierre

PS I hope I did not step in it by posting what I had found in the earlier reply.
 
Pierre,
If you would like, you can email me the PDF and I will get help to post it into the archives so that it will remainn available for others to see and use. You can PM me and I will give you my street email address and you can do a cut an paste of the info and I will do the rest for you. Hope this helps.

Bob
 
The PDF is the one item that did not get copied properly, so it is lost on my system.
Pierre
 
Here's the no-contact sensor I ordered after reading many good reviews on it. Either affix the reflective tape to your chuck or maybe put a threaded collar on the outboard side of the spindle and affix it there. Remember, we're talking about RPM, not SFM, so diameter of chuck doesn't matter.
 
I have one of those and it is not worth the plastic it is made out of. You can get ten different readings after ten different trys at the same speed not knowing which one is accurate. I also tried it on a known RPM and it was off by a little over 200 rpm. Ray
 
Aha! Being a file-pack-rat FTW....

(hope that's what you wanted anyhow!)
 

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