Hi,

I’m new here so if I post this in the wrong category, please forgive me.

I need to make a tachometer for use on a lathe. Does anybody have suggestions for a circuit that I could use to make one?

Thanks, your help is greatly appreciated!

 

A tachometer is simple (google for 555 tachometer), it's getting the pulses that are the more difficult part - is there anything there already you could use?.

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Nigel,

Thanks for the response!

For the pulses I was thinking of putting a slotted disc on the spindle under the gear cover so it would be of the way and out of sight. Then I would use some sort of light pickup to count the pulses. Does that sound okay?

I'll google "555 timer" and see if anything shows up but I haven't had any luck finding a circuit so far.

Thanks...

Mike

 

Yes, that sounds fine - you could use a sloted opto-switch to read it (it's what they are designed for).

Like I said above, google for "555 tachometer", "555 timer" will find the same, but a LOT more you don't want.

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PIC programmer software, and PIC Tutorials at:
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Nigel,

The Opti-switch looks great! But... I still can't find a circuit for the tachometer. I was hoping for a digital display circuit. The google search for 555 tachometer returns lots of 'talk' about one but not an actual circuit. Can you or anyone else point me in the right direction for a schematic that I could use to build one?

Thanks!

Mike

 

A 555 can be used to make an analogue tachometer, basically just a monostable - it's been used for years in cars etc.

If you want a digital readout the obvious way to go is to use a PIC, which along with an LCD display would give a single chip solution.

The magazine EPE did a suitable project called PICAgoras a long time ago, you can download the code for it from their website - and this is the circuit.

BTW, this is quite old, and uses an old LCD that needs a negative voltage - modern ones don't.

Attached Images

Pic_Agoras1.gif (448.9 KB, 188 views)

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PIC programmer software, and PIC Tutorials at:
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Nigel,

Thanks for posting that circuit! I appreciate the time you took to not only find the page but also to scan and upload it for me.

I have to study it for awhile and see if I can figure out what it's doing and how it works. So...I'll probably be back asking you more questions.

Well...here's one right off the bat...Will the LCD's that need negative voltage be a problem and if so, is there a work-around for that?

Mike

 

You probably won't be 'quite' so appeciative when I tell you I scanned it a few years ago for someone else, and just had to upload it!

Essentially everything is done in the PIC, it counts (or times) the pulses, converts the value to sensible units, then displays it on the LCD. It's more the programming that's 'clever' rather than the hardware.

Modern LCD's don't need the negative voltage, so you can just leave out the diodes and capacitors associated with it, and connect the contrast pot to +5V instead. Check my tutorial hardware if you want to see how it connects.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

Does it need to be accurate? 555's are not. Digital tachs simply count the pulses for a defined time period. A counter, a slow gate oscillator (sometimes a xtal and a BIG divider ) osc, and a register.

D.

 

Ok mbu,

here is link to what your looking for.

http://www.josepino.com/pic_projects...tachometer.jpc

Great stuff there.

On my lathe, I use optical sensor, and it works great. I just painted a mark, about 1 inch wide, on the chuck. It has no problem reading 2500 RPM, and good down to 28 RPM.


Have a good day.

 

Thanks to everyone!!!

Nigel,

Thanks for the information and I do appreciate your help, even it it's just an upload. Thanks for the explanations too - I'll go over what you said and the circuit so I can understand what's going on.

hjl4,

Wow, that is a great site! I'll have to try that circuit since it looks so simple and all the programming is done for it.

When you built your tachometer, where did you buy the parts and did you need any special software or hardware to load the program on the PIC chip?

Again, thanks everyone!

Mike

 

It wasn't too complicated, I looked at building my own JDM programmer, and then learning asm language, and then experimenting and bothering a lot of people on this site for assistance. I am still learning.
Once the programmer was built, it was a matter of downloading ICProg, and I was on my way.
If you want valuable help, follow Nigel's tutorial, and you will have it made. Even though sometimes, I needed clarification, understanding the principles of some of the code he has with each of his tutorial. It can get overwhelming sometimes, so I just take a break once in a while, and if I can't figure it out, then I post a thread on this site.

Practice makes perfect.

Nigel has all the schematics for the hardware you will need to complete his tutorials, up on his site, just follow the schematic and assemble them ect...
The tachometer was built with a Fairchild optical sensor, which I got as a sample from them, and the spindle had a flat black paint mark on it.
The rest was simple, just follow how Josepino has his wired up, (schematic) and you will succeed. He even has BOM included so you can go shopping, knowing you have all the right parts.

All my parts I got from work.
But you can get yours at Digikey, or a friend etc....

Good Luck!

 

hjl4,

Thanks!

I may have a few questions for you as I go along.....Would you mind if I sent you a private message if I have some questions? The questions most likely won't be for a while as I have to review all the information on Nigel's site and study the circuit.

 

IF it was my lathe I'd mount a 6" Monster tacho with a big yellow shift light...even if i could'nt figure out how to send a signal to the damn thing

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2.4Gigglehurtz

 

Now that sounds tasteful! - I hardly dare ask what you drive?

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk