Thread: Hand Held RPM meter (tacho)

I have got one very similar and it works a treat. You have to put a bit of reflective tape on the chuck or what ever turn the machine on and you have your reading immediately. It runs on AA batteries but you right it can hide pretty well when you put it down

Have a look at these, a much cheaper option, I bought one around a month ago.

Originally Posted by KevM

Have a look at these, a much cheaper option, I bought one around a month ago.

I have one of these - I bought it 4 years ago on ebay when it cost $60. Sometimes we forget how much some of the cheap consumer items have come down by.

I've got one that looks virtually the same, but I payed I think under ten bucks for it on fleabay, straight from Hong Kong. Who knows how accurate it is? All I can say is it seems to work fine.

Edit: Dude, did you post this thread twice?

I looked at these a while back and all the cheaper ones seem to be pretty much the same, so don't go spending $20 odd dollars as it will probably be the same as the $10 one.

The next step up is one that also read super feet a minute and meters a minute, they are up around $40+ dollars and have a little wheel attachment for contact and will also work as non contact.

Dave

I built my own tachometer using a microcontroller board (an arduino clone called RBBB), a 16x2 LCD and a hall-effect sensor.

With a tiny rare-earth magnet hot-glued to a shaft or pulley, it displays RPM. Also, if you select a work diameter (using up/down buttons in 5mm increments) it reads out the surface speed directly.

impresive

We have one here at work and it seems to work fine. As Bryan said, who knows how accurate it is but it would be fairly close I'd think. At the end of the day, for machining purposes, it doesn't really matter if its out a little bit anyway. If your machines are gear or belt driven you will probably only need to check them once. I borrowed the work one to check the speeds of my drill press. then just made a chart with the various speeds for the different pulley combos, laminated it and stuck it to the side of the drill press.

regards
bollie7

Hi Jack,

There is an article in last issue (I think last issue) of MEW that makes a digital tacho out of a bike trip computer for under $10. Some bicycle trip computers have an RPM function, so you can connect this to your spindle and have the readout at a convenient location. It's on my "to do" list just for a fun project. Looking on ebay, you can pick them up from Honkers for about $7 - $10.

Also the accuracy of any of these methods including the handheld optical ones would be plenty for determining the RPM for turning speeds. I would imagine they would have a typical error of about 1%. So even at 2000 RPM, error would be no more than +/- 20 RPM.

Just an idea.

Simon

I got one of these a while back from Hong Kong. $19 landed at my door, looks like the price has dropped even more.
It looks exactly the same as the one in Jaycar.

thanks for the replies fellas. I'm glad I asked here before going to Jaycar. The Jaycar one looks exactly the same only 4 times the price!

PS I managed to post this thread twice. No idea how.

First up, sorry for posting this thread twice. No idea how that happened. Maybe I got impatient and hit SUBMIT twice.

Thanks for the feedback. I like the bike computer idea. I should probably know, but what is MEW Simon?

unixbigot, do you have a source for the microcontroller board? did you write the code yourself or is it available "out there" in the ether?

On the sister version of this thread there is an ebay link to a hand-held that looks exactly the same as the Jaycar one but for $14! I reckon I'll get one anyway and investigate the other options for later.

Edit: added question for unixbigot.

unixbigot, that looks like a nice little project where I could generate smoke instead of swarf.

I couldn't find much on Mr Google but I was probably searching for the wrong thing.

Are plans/instructions in the public domain?

Cheers,
Matt

Hi jack,

Its a magazine called Model Engineers Workshop. Its an english publication that is found in most larger newsagents. I buy it from time to time as part of my pursuit for knowledge in metal work and turning.

BTW I wouldnt consider it to be manditory reading just because you have an interest in metal work but I have found it an interesting read from time to time especially articles from Harold Hall. His descriptions and explanations tend to cater for and are often aimed at people with limited experience.

Cheers.