Wow - huge price difference

[nearnexus]

Bought one of those cheap digital laser tachometers off of Ebay for $12 AU (delivered) ex Hong Kong.

Good deal.

Dropped into Jaycar Electronics for a browse.

Exact same tachometer for $79.95 AU.

Gawd, that's some sort of mark up.

I don't mind a mark up to allow buy it now stores to cover their costs, but that's outrageous.

Rob

[jack620]

Yep, I bought one too a while ago. Fraction of the jaycar price delivered to my door. They work well too.

[morrisman]

Yes me too

I purchased one from Asia two years ago. It seems to do the job well. Handy gadget to have . I calibrated the DM 45 mill drill and the Sheraton lathe . Mike

[nearnexus]

I was stunned by the price difference. Talk about gouging.

I intend to use mine as a built in tachometer on my lathe.

I'm converting it to variable speed using a 2 HP 180 v DC motor and a KBIC-240DS controller (ex USA).

The idea is that you gut the tacho, take the laser and sensor off the board and mount them and the lens remotely.

Just put them on some PCB at the same spacing and wire them back to the circuit board.

They fire at the spindle shaft and the display and circuit board find a home on the lathe headstock.

Short out the on off switch and your good to go.

A guy in the 10x22 yahoo groups has done it already - beat me to it.

You dump the battery and just use a 9v power pack.

Love dem mods :)

Cheers

Rob

[simonl]

I used to work at Jaycar Electronics. All staff were entitled to staff discount which was cost + 5%. I couldn't believe how cheap the stuff was! On one occasion I bought a $50 kit for about $12!

Simon

[Stustoys]

They arent the worse by a long shot.
I have one of their older IR thermometers, cost me around $50 for Jaycar a few years back. I saw the same thing in a link on this forum listed at $275(I think it was +gst)

Stuart

[nearnexus]

Jaycar are generally OK given they are a buy now store and 100% mark up is normal.

But this one blew me away.

Rob

[jack620]

A guy in the 10x22 yahoo groups has done it already - beat me to it.

Do you have a link Rob? Or can you copy across a few photos? I'd like to try it. I currently use a Cateye bicycle computer as a lathe tacho. It works pretty well, but is inaccurate at low RPMs.
Chris

[nearnexus]

OK. I did down load the most relevant photos for my own reference - I'm a member.

Give me a few moments and I will put them on my web server and you can see how it all comes together .

Rob

[nearnexus]

OK guys and gals here it is - click on info below and see how you too can have a fancy LCD tachometer in your lathe headstock for only $12.

info (http://users.tpg.com.au/agnet/info.html)

I can see a few people dusting off their soldering irons for this one.

Cheers

Rob

[jack620]

thanks Rob

[toolman49]

G'Day Fellas,
I got screwed, I paid $18.00 for my laser tacho, in view of the price of these units I wonder if the internal components are up to continuous use in a spindle speed application ?.
I recently spotted a built up LED tacho module on Ebay for about $12.00, just need to add a photo sensor and power supply, I have one on order and should be here around the end of the month.
Rob,
I run a D.C. motor and KBMM controller on my lathe and it works a treat.
Regards,
Martin

[nearnexus]

What motor HP and voltage are you using Martin?

Also what 5 k ohm potentiometer are you using ? - small, big ? How much volt/amps does it have to carry ?

Rob

[toolman49]

Hi Rob,
It's a 1.5 H.P. 180 volt D.C. motor, the pot is a standard 24mm dia .5 watt linear slope, it only carries control voltage, the SCRs on the board carry the actual current. FYI during final setup and testing a 2.5mm DOC @ .1mm/rev @ 500 RPM in 50mm mild steel pulled 3.2 Amps @140v . The KBMM is set to 170 volt maximum. The controller is mounted on an auxiliary heatsink which probably wasn't necessary. After 2 years of light use (2-4 hours a week) the brushes and commutator are as new. It was a lot of work at the time but worthwhile.
Regards,
Martin
P.S. it is essential that you install the correct horsepower resistor or the current compensation will go batshit.

[nearnexus]

Hi Martin,

Thanks for that.

CBC have the resistors as they are the Baldor Distributor in Oz - who handle KBE gear. About $10 each.

So no problem there.

I have a 2 HP 180 V DC motor out of a SportsArt 1210 and it's an awesome piece of gear. Replacement motor cost $400 - $600. This is a continuous duty motor.

These treadmills were $2500 new, and when they go kaput they cost an arm and a leg to repair, IF you can get the parts. So they get turfed. Thank you very much :)

Got the treadmill for nothing off of Gumtree - built like a tank and I've spent this afternoon cutting out the motor mount plate to cut up to make the lathe mount.

I'm using a KBIC - 240 controller and they recommend the auxillary heatsink be used for 2 HP applications (which is the maximum for this controller).

These are not cheap, so I'm just going to bolt the controller to the original power supply heatsink, which is just a massive piece of aluminium flat plate.

Should be more than adequate.

As you say, it's quite a bit of work to set it up correctly.

The original motor fan was pretty pathetic, and I intend to use a large PC power supply fan to blow air through the motor. Will run it off the tacho power supply if the volts agree, otherwise will just use another power pack.

Will take a while to get this all sorted, but looks promising.

These big treadmills also have a smaller 32 V DC motor for the incline function. These would make great motors for a miil powerfeed, or a small tool post grinder etc.

Cheers

Rob

[Ueee]

G'Day Fellas,
I got screwed, I paid $18.00 for my laser tacho, in view of the price of these units I wonder if the internal components are up to continuous use in a spindle speed application ?.
I recently spotted a built up LED tacho module on Ebay for about $12.00, just need to add a photo sensor and power supply, I have one on order and should be here around the end of the month.
Rob,
I run a D.C. motor and KBMM controller on my lathe and it works a treat.
Regards,
Martin

Hi Martin,
Do you have a link for that tacho?

[toolman49]

Hi,
The Ebay seller trades as skt flyer.
Rob,
Have the manual for the KBIC controller, let me know if you need a copy. I have no idea of your level of electrical knowledge or experience so please get get qualified assistance if you need it as high D.C. voltages are lethal.
Regards,
Martin

[jack620]

Martin,
that link you posted doesn't work for me and I can't seem to search for a specific seller on ebay. Can you post a link to the actual item you bought?
Chris

[.RC.]

skt flyer items - Get great deals on Wires and Connector, LED items on eBay Stores! (http://stores.ebay.com.au/skt-flyer)

[jack620]

Thanks RC

Martin,
have you managed to source a reasonably priced optical sensor?
Chris

[toolman49]

G'Day Chris,
If you want a photo interrupter to read a moving vane, Jaycar have their ZD 1901 @ $3.50 or if you want reflective (much nicer in my opinion) uxcell in HK have their EE-SPY412 @ $9.25, I have found uxcell pretty quick with their delivery, small items in an envelope usually arrive in about 7 days.
Regards,
Martin

[jack620]

Thanks Martin, the EE-SPY specs look good. Have you nutted out a circuit yet?

[toolman49]

Hi Chris,
I am waiting for the tacho module to turn up before I make a decision as I have choice of used sensors in the junk collection, the EE sensors are an Omron product and you can download application notes from their website, they claim that you must use their connector, but I have found you can safely solder to the pins if you heatsink them and work quickly.
Regards,
Martin

[Ueee]

wouldn't it work just as well with a hall effect sensor? One on a gear somewhere would do the trick as the tacho has a division input, ie how many spikes per rev.

[jack620]

I thought about that Ewan, but I don't know whether a hall-effect sensor is sensitive enough to resolve individual teeth on a lathe gear. I've never used one. Does anyone know?

EDIT: would this method improve resolution at very low RPMs?

[Ueee]

My wife's car has toothed wheels, maybe 1/2" c to c teeth, presumably with HE sensors for speed, revs and crank position (the one on the front of the engine that counts revs is missing a tooth). This is 23 y/o tech we are talking about. Depends on the DP of the gear i guess, i don't know if i have a HE sensor handy, i might order some and hook them up to the oscilloscope and have a look at the waveform they create at a decent speed.

Edit, here is the 3503 data sheet. the only real problem in the presence of a magnet on the sensor which may attract swarf. http://www.jaycar.com.au/products_uploaded/ZD1902.pdf
2nd edit, i'll order some 3144's, they have a build in voltage reg so can run off 4-24v

[jack620]

Great, I'm keen to hear the results.

[toolman49]

G'Day Fellas,
You buggers must have been peeping through my workshop door, went through the junk today and dug out a HZK-101 Hall sensor, checked it out and it gives a nice fat 12 volt switching pulse. I knocked up a single hole sector plate tonight and will post a photo when the paint dries.
Regards,
Martin

[nearnexus]

Hi Martin,

I'm pretty OK with electronics (basic stuff) so I'm aware that 180 V DC can be lethal and that capacitors take a while to wind back :)

Just in case anyone is interested I have 5 brand new KBIC-240 DC controllers comming in from the US in the next few weeks.

I will be using one and selling the rest at $65 each plus postage or pickup.

So if anyone is interested ping me an email.

I also have a second hand KBIC-240DS (thats 240 AC to 90 DC) that I will probably move on for the same price.

There's no warranty or returns on this stuff.

I'm in Adelaide.

Cheers

Rob

[Greg Q]

I already have a Baldor variable speed converter/controller. What I'd like is a suitable motor. Where do you source yours?

Greg

[nearnexus]

I just keep an eye open on Gumtree for free treadmills. I'm going to pick up one this arvo :)

It's a Repco one and I believe the motor is 1.5 HP - probably be 180 V DC.

I've got a 2HP motor I'm machining up a conversion mount for my lathe at the moment.

So lots of lathe surgery ahead.

BTW these treadmills are damn heavy. Lots of steel and sealed bearings and other interesting bits that you can use or take to the scrap man to cover your diesel/petrol.

But then again if you had some fat overweight jogger jumping up and down on you, you'd want to be strong.

Rob

[Greg Q]

What's the RPM range of those motors? I have an application that just needs on/off and variable speed. I was going to employ an AC servo but a free DC motor would be much simpler.

Greg

[simonl]

I picked up two treadmills (life fitness 9000) from a gym that had left them outside in the carpark. The bits and pieces that I used from just one of them lasted many many projects and has been a tremendous source of great parts.

If you see one going begging, pick it up and worry what to do with it later. Believe me you will be happy you did once you start taking it apart.

Simon

[nearnexus]

Yep, great things to grab. Apart from the motors they may have Allen headed metric bolts, sealed bearings, hall and optical sensors, rubber coated rollers, steel roller shafts, aluminium roller bearing housings, "V" or serpentine belts, circuit boards and power supplies with lots of reusable components.

And then there's the steel frame, tube arms, and base as well.

Attached are photos of the two motors I salvaged.

The one still in the frame on the right is a 1.5 HP 180 V DC. (170 mm motor case length) - just got that one this arvo. And the mainboard/unit actually still works.

Nice big heat sink there. They're about $20 to buy.

The other is 2.0 HP 180 v DC (210 mm Case length) Quite a lot bigger for the extra 1/2 HP.

Both 0 - 4300 rpm.

Really well made motors. These have a 100% duty cycle.

The only problem with these motors is that it's almost impossible to retain the rather poxy fan during conversion - if you want to keep metal cuttings out of the motor.

Rob

[toolman49]

G'Day Fellas,
Photo of Hall sensor and sector disk attached, can't do much more until the tacho module turns up.
Regards,
Martin

[jack620]

nice job. where do you intend mounting the disc?

[toolman49]

G'Day Chris,
The disk will go between the 2 locknuts at the end of the spindle,
Regards,
Martin

[jack620]

Martin,
I have a Hercus 260 which has a different spindle arrangement to yours I guess. I'll have a look inside and see if there's anywhere I can mount a similar disc to yours.
Chris

[Ueee]

Chris,
I'm in the same boat, i was thinking of trying to pick up the pulley to bull gear lock, the thingy you pull out when you engage the back gear. (not sure what it is called)

[jack620]

Ewan,
Hercus just call it the "bull gear lock pin". That might work. I still think having multiple slots would greatly improve the resolution at low spindle speeds. Hopefully Martin will get his tacho soon and all will be revealed!
Chris

[Ueee]

The data sheet i linked to before shows a sensor on a gear, this may be ok for low speeds but not for high speeds, we shall wait and see. I have ordered 20 3144's cost me $3 (don't ask me how they can even ship them from china for that) and a tacho, but i'm sure Martin will have his first so we will just have to wait.
Martin, once you have it setup did you want to start a new thread so it doesn't get lost on the end of this one?

[Stustoys]

The data sheet i linked to before shows a sensor on a gear, this may be ok for low speeds but not for high speeds,
Why you say that?
If I'm reading it correctly(about a 50% chance) it will operate up so 23kHz
So even if the spindle speed in 4000rpm wouldn't the bull gear need more than 345 teeth before you had a problem?

Or do I have it all wrong again?

Stuart

[Ueee]

Why you say that?
If I'm reading it correctly(about a 50% chance) it will operate up so 23kHz
So even if the spindle speed in 4000rpm wouldn't the bull gear need more than 345 teeth before you had a problem?

Or do I have it all wrong again?

Stuart

You are right Stuart, but just cause it works on paper doesn't mean it will work in the real world!

[Stustoys]

Hi Ewan

but just cause it works on paper doesn't mean it will work in the real world!
For sure(as my lastest light bulb replacement proves lol)
Stuart

[toolman49]

G'Day Fellas,
The tacho module turned up yesterday, but haven't had much time to play with it as I am up to my goolies in real (paying) work, did a quick hookup to the existing PE sensor and it looks pretty good. I need a bit more time to play with the multiplier and decimal point as I don't think I need resolution down to 1/10th of a rev. (Yes, the lathe does go down to 6 RPM in back gear).
Regards,
Martin

[jack620]

Excellent! Keep us posted. Meanwhile I'll order one too.

[Ueee]

Mine will probably turn up next week while i'm away so i'll just have to wait.....Good to see that it worked well, 6 rpm, i think thats even slower than the Leblond will go! (13rpm i think?)

[nearnexus]

Martin,

I have a Hall sensor (two wires) and magnet from one of the treadmills.

How do I determine if it is suitable for this tacho ?

One lead has a dotted line down it and the other has a single unbroken line.

Rob

[Ueee]

Martin,

I have a Hall sensor (two wires) and magnet from one of the treadmills.

How do I determine if it is suitable for this tacho ?

One lead has a dotted line down it and the other has a single unbroken line.

Rob

Rob,
Does it have a code on it? All the HE sensors i have seen or used have 3 wires, V+ ground and a Data line. If it doesn't have a code on it the only other way to tell is with a oscilloscope. Don't be too worried, i ordered 20 so i'm sure i could send you one (at 15c each it won't break the budget:D)

[nearnexus]

I couldn't see any code on it - only the treadmill name.

Looking at the specifications on Ebay for the tacho and the various connections shown, am I correct in that the image on the far right under pin definition is for a Hall sensor?

If so, it only has two wires. Or have I got it wrong ?

As you can guess, I'm no whizz on this type of electronics :(

Rob

[toolman49]

G'Day Rob,
It sounds more like a reed switch, especially if it operates with a magnet, Hall sensors are usually switched with an iron vane, as Ueee says Hall sensors usually have 3 leads. I am not sure if a reed switch would respond fast enough for a tacho application. I had a quick play today using a Sick reflective sensor with a single segment sector plate (1/2 reflective, 1/2 black) the display was perfectly stable, not even 1 RPM variation at any speed. So I am rethinking the Hall sensor. (I know I change my mind more often than a woman).
Regards,
Martin

[nearnexus]

Hi Martin,

You are probably right on that. Anyway I like the idea of the red LED tach, and it would be a lot easier to fit into my lathe head than the LCD job that's comming, so I too will buy one from Ebay - before the big 5% sale ends :)

Then when you have yours setup nicely I will buy the same bits to get mine going.

Update : ordered the red LED display.

Also rummaged around in my electronics stuff and found the bits in the attached photo which look to be a "real Hall sensor" and a sector disc :)

What do you recon guys ?

Rob

[simonl]

Hi Martin,

You are probably right on that. Anyway I like the idea of the red LED tach, and it would be a lot easier to fit into my lathe head than the LCD job that's comming, so I too will buy one from Ebay - before the big 5% sale ends :)

Then when you have yours setup nicely I will buy the same bits to get mine going.

Update : ordered the red LED display.

Also rummaged around in my electronics stuff and found the bits in the attached photo which look to be a "real Hall sensor" and a sector disc :)

What do you recon guys ?

Rob

Ok. Hook, line and sinker! I've been watching this I you have sold me on the idea. I bought one last night with the massive 5% discount!

Rob, that notched signal generator and hall sensor looks the goods! Looks like it's more suited to a vehicle with ABS than for a lathe!

Lots of signals per revolution so you should get a nice stable reading to very low RPM's.

The reed switch option would be OK at low RPM but there would become a stage where the signal frequency generated by the notch would be too great for the switching speed of the reed switch especially with more notches (creating more pulses) per revolution. A hall affect sensor is the more elegant method of use.

Can't wait to get mine now!

Cheers,

Simon

[jack620]

I just bought one too.

Re the reed switch- my current tacho is a bicycle computer. It works well at the max RPM of the Hercus 260. Initially I will try the LED tacho module with the reed pickup from this setup to see how it goes. I agree that HE or optical is more elegant though.

Chris

[nearnexus]

Thanks Simon.

OK so which of the connection settings shown in the diagrams on the Ebay page for the tachometer are for a Hall sensor?

I suppose a multi edge notched metal disc would be just as good as the plastic job in the photo ?

While I had the camera going, heres a shot of how the dual cooling fans are being attached to the treadmill motor for the lathe conversion.

I could have made it round externally (rather than square) and used a big hose clamp to compress it, but used a bolt instead.

I machined up some recycled polycarbonate and clamped it to the motor as the fan mount. They suck air through the motor from the drive belt chamber and will run off the same 12v power pack as my new red tacho.

As polycard is a bit slippery, to make sure it stay's put I machined a groove on the inside clamping surface of the polycarb and used silicon between it and the motor and let it harden before clamping up.

Rob

[Ueee]

If the wheel in the pic is plastic and part of the original use of the switch I would say that it is an optical sensor, but it should work. Yes the gar right pic is the one you need, but you have to work out which wire is which......

[nearnexus]

Your right Ueee. It's optical.

I found a parts list for the treadmill and it's definitely optical.

Rob

[simonl]

I'm getting rusty (not that I'm an expert!) yes now you mention it, it is an optical photo interrupt or sensor. They work just as good!

In regards to the notched pulse generator, any material is OK but dark or black in colour is always better. It reduces beam reflection and false triggering and hence potentially erratic display.

In terms of the pin out, most photo interupters are similar. They should not need too many external components to drive them, maybe a resistor or two as they generally have inbuilt transistors or op amps to buffer the output.

Do a search for photo interrupter. The one in the attached image just needs two resistors. The one on the output is there to clamp the output to digital 0 in the absence of a signal. This stops the output from "floating" if there is no signal (beam is blocked). This ensures that the output is either 0 or Vcc and nothing in between.

In terms of resistor values. The resistor value of 50 ohm seems way too low. I would have thought maybe a 560 ohm. This would produce a current of 21mA @12V which is pretty much a norm for photo diodes or LED's. One resistor on the output is less critical, perhaps a 10K ohm would be fine.

Google Image Result for http://www.buildlog.net/cnc_laser/images/photo_interrupter_circuit.png (http://www.google.com.au/imgres?q=photo+interrupter&hl=en&sa=X&biw=1440&bih=731&tbm=isch&prmd=imvns&tbnid=vHJ3pkoeODa4_M:&imgrefurl=http://www.buildlog.net/cnc_laser/buildlog_2.html&imgurl=http://www.buildlog.net/cnc_laser/images/photo_interrupter_circuit.png&w=460&h=266&ei=4itAULjjNseSiQeiqIGQCQ&zoom=1&iact=hc&vpx=166&vpy=155&dur=9791&hovh=171&hovw=295&tx=106&ty=117&sig=110803276876338865393&page=1&tbnh=108&tbnw=186&start=0&ndsp=29&ved=1t:429,r:0,s:0,i:73)

Cheers,

Simon

[simonl]

Thanks Simon.

OK so which of the connection settings shown in the diagrams on the Ebay page for the tachometer are for a Hall sensor?

Rob

OK. First of all, Rob I love your work! Your DC motor conversion looks great!

In terms of the connection:

You will be using the same power supply to drive both the photo interupter and the display? If so then the same ground in common to both and they will both be run from same Vcc. Since the output of the photo interrupt is NOT inverted, ie when the beam is at one of the notches and the beam is transmitted then you will get an output of 12V so I would use the diagram on the far RHS. The tacho has an input impedance of 10K so you should be able to connect the output signal straight to it. You obviously still need the 10K clamping resistor (assuming it's similar to the one in the image I attached) also the signal voltage needs to be between 3 and 30V which it is since you running off 12V

You would be very unlucky indeed if you connected it wrong and you let the magic smoke out! :2tsup:

Good luck

Cheers,

Simon

[nearnexus]

You recon your a bit rusty, but your still way ahead of me on this stuff :)

Here's a photo of the back - if that's of any use.

Update: OK thanks for that Simon. I hope I get mirrors and not smoke :)

I'm still waiting for my batch of KBIC-240 drive controllers to arrive from the USA, so I'm just cruising along on the conversion with lots of time to think about options etc.

The original AC motor was end mounted and the donor is not, so I've had to weld/machine up a cradle to take it. The other option was to pull it apart and make up a new end plate and bearing holder, but that was going to be a lot of work with cooling holes, through bolt locators and possibly key mounts for the main case.

So doing it this way. Looking good so far.

I just hope the 2 HP DC motor has enough power in comparison to the existing 3/4 HP AC unit - which is ideal.

Rob

[simonl]

OK. I just had a look a the data sheet of the photo interupter from Jaycar. The input runs on 6V MAX. The output is a little more flexible. I was going to say that you may need to run it from a 7806 which is a +6V regulator but looking at your circuit board it seems like it may already have a voltage reg on the board. That may make things easier for you (if that is the case)

In regards to the 3 wires. Usually (And I mean usually) black is Gnd, red is Vcc and the other colour (green in this case) is usually the signal output.

There seems to be a small tantalum capacitor on the board, thats either to reduce noise or it maybe on the output of the voltage reg if it has one. You would need to look closely at the chip and follow the circuit.

http://www.jaycar.com.au/products_uploaded/ZD1901.pdf
Hope this helps.

Simon

[simonl]

You recon your a bit rusty, but your still way ahead of me on this stuff :)

I just hope the 2 HP DC motor has enough power in comparison to the existing 3/4 HP AC unit - which is ideal.

Rob

I'm not an expert on the comparisons between AC motors and their equivalent in a DC motor but I would have thought that HP is HP is HP and that a 2 HP DC would trump a 3/4 HP AC motor. Can't be too sure though.

Even if DC motors are less efficient and the power rating is the amount they draw and not what they put out, you are still 2.5 times the power of the AC motor.

Simon

[nearnexus]

Thanks Simon.

Regarding the HP rating difference between AC and DC, the one thing that suggests that power may not be an issue is that the existing AC motor has an RPM of 1450, the new motor has 4300 RPM, a factor of nearly 3X.

As I want the new motor to spin the lathe up to about 2000 RPM (V's the current 1800) it means I will be gearing the new motor down with the pulley system by 3:1.

That should produce a pretty massive torque effect for the same spindle speed.

Throw in the supposed HP difference and things get interesting.

If you get my drift :)

Rob

[simonl]

Love it when a plan comes together!

I have been looking at the underside of the photo circuit board. It's doing my head in!

I'm not sure what the function of U1 is. Not sure if it's an op amp or something. Some one else may know. the wire configurations seems to be what I said but the photo interrupt is powered directly from the red wire so if you give it 12V then it will receive 12V.

R1 is simply to limit the current in the output
R2 + R4 seem to play a part in setting the input current for the diode
R4 also acts as a clamp or pull down resistor for the signal output

Don't know what U1 does :no:

BTW does you lathe have a gearbox to change speeds? If so, are you planning on bypassing the gearbox and put the pulley on the spindle or still going through the gearbox?

Cheers,

Simon

[Ueee]

U1 looks like an op amp, is there a no. On it? If it is an op amp the signal will probably be inverse, not that it really matters.

[nearnexus]

Had to go get the jewelers eye piece for that one.

U1 looks like LM393 or LM398 - damn near impossible to read.

No gearbox on the lathe, all belt drive, and am using the existing pulley system except for the motor (4 step pulley) where I am using a single step pulley same size as the existing lowest gearing size (but that's fine as it's the one you use the most for the various speed combinations.

BTW my LCD digital hand held tacho arrived this arvo ($12 delivered which started this thread).

It's great. I tried it out on a few things ( lathe spindle, lathe motor, bench grinder) and it's super stable and seems pretty accurate.

I also tried it with a chalk mark rather than the reflective tape and it worked quite OK. You have to move a bit closer with the chalk but it's no big deal.

Also it works right down to just a few millimetres which is much closer than the spec says, so it could be crammed into pretty tight places if you wanted to make it permanent.

A mate made up one of the Jaycar kits years ago that had a very similar function and this is way way better than that. The Jaycar one was very feeble and hopeless in light conditions, and I don't think it used a laser, just a photo cell of some sort.

Nice big LCD display on this one too. It's not worth the price Jaycar are asking, but at $12 it's damn good. Pretty gutsy laser on it.

And I even got a free battery with it - beat that :)

Rob

[Ueee]

It's an op amp/linear comparator. It has 2 inputs, it compares the 2 input voltages and turns on or off depending on which is higher. Basically it is just there to clean up the signal to a true square wave, as what comes out of the sensor may not be clean.

Just to add to that, r2-4 probably make a voltage divider to give the LM393 something to compare the voltage from the sensor to.

[nearnexus]

Thank Ueee, I'm none the wiser.

This is all way beyond me. So in the Queen's English how do I connect this sensor up?

I really appreciate you and Simon's help on this.

If this is not the best way, let me know. I don't mind spending a few dollars to get the right result.

Rob

[Jekyll and Hyde]

Heh - I think the Chinese are reading this thread! I went looking for one of those $12 laser tachos when you started this thread, and managed to get one for about $10. Just clicked on the item description wondering if mine was likely to arrive with a battery, and they're now listed for about $20! Perhaps the 240 odd they've sold with free postage have actually cost them money. :D

Good to know that chalk lines work, means you don't have to bother digging up reflective tape all the time! It should probably work with a white paint pen too, I suppose..

[toolman49]

G'Day Fellas,
Just got in after a truly psycho day in the field, here are a couple of quick photos of the sector plate and sensor and rough temporary housing for the display. I need a shower, a feed and a couple of drinks, so see yuz later,
Martin

[simonl]

It's an op amp/linear comparator. It has 2 inputs, it compares the 2 input voltages and turns on or off depending on which is higher. Basically it is just there to clean up the signal to a true square wave, as what comes out of the sensor may not be clean.

Just to add to that, r2-4 probably make a voltage divider to give the LM393 something to compare the voltage from the sensor to.

Give that man a Cigar! Ewan I think you are right on the money with that. Also, do you think Rob should run the photo sensor straight from 12V or bring down the voltage to about 5V?

I think he should be OK to run the green (signal output wire) straight to the signal input of the tacho. With the input impedence of the tacho and the buffered output from the op amp it should be all good. Just don't know about driving it at 12V.

Simon

[simonl]

G'Day Fellas,
Just got in after a truly psycho day in the field, here are a couple of quick photos of the sector plate and sensor and rough temporary housing for the display. I need a shower, a feed and a couple of drinks, so see yuz later,
Martin

Thanks for the pic toolman. I think i will copy your setup when my tacho arrives. If I'm happy with the outcome then I may even lash out and buy another for the mill! :U

Cheers,

Simon

[simonl]

BTW my LCD digital hand held tacho arrived this arvo ($12 delivered which started this thread).

It's great. I tried it out on a few things ( lathe spindle, lathe motor, bench grinder) and it's super stable and seems pretty accurate.

I also tried it with a chalk mark rather than the reflective tape and it worked quite OK. You have to move a bit closer with the chalk but it's no big deal.

Also it works right down to just a few millimetres which is much closer than the spec says, so it could be crammed into pretty tight places if you wanted to make it permanent.

Nice big LCD display on this one too. It's not worth the price Jaycar are asking, but at $12 it's damn good. Pretty gutsy laser on it.

And I even got a free battery with it - beat that :)

Rob

Yep. Once again thanks to another thread a while back I ended up buying one of them too. Very handy indeed and same same about repeatability and stability. My only gripe is that it seems every time I go to use it (once every 3 months or so) the battery is flat! I think I'll store it without the battery in.

Thanks for the info on your lathe. I was just wondering what people did when they convert to variable speed electric motors if they have a gearbox. Ideally I would love to by-pass the gearbox if I put a variable speed motor and have the motor connected by pulley straight to the spindle but I'm not sure if that's wise. This treadmill motor I have ATM runs flat out at 5000 RPM which is 2X what I would possibly ever need!

By-passing the gearbox is probably making the set-up more complex than it needs to be. I just thought it would be nice to remove some of the unnecessary gear noise.

Simon

[nearnexus]

Simon there is another thread going about which lathe to buy, and one being considered was the TL250V Titan which is variable drive.

It just direct drives to the spindle via one of two spindle ratios.

Titan Machinery - TL250V PIC (http://titanmachinery.com.au/index.php?option=com_content&task=view&id=203&Itemid=499)

But if you have a gearbox you would still need to take the gears out of mesh somehow to stop them freewheeling off the spindle, with the alternative drive system being used.

Gets complicated.

PS regarding the battery going flat on the LCD tacho I did notice that when you put the unit back into it's snazzy little blue carry bag, it can very easily turn itself on in the bag just from light pressure on the switch. Maybe that's what's happened ?

Regarding the optical sensor voltage, I do have a 7 volt DC powerpack - would it be wise to try it off that first ?

Rob

[Ueee]

Give that man a Cigar! Ewan I think you are right on the money with that. Also, do you think Rob should run the photo sensor straight from 12V or bring down the voltage to about 5V?

Simon

I would go to 5v, not knowing what voltage it should be run off makes it hard. Unless of course Rob you can hook it back up and test the supplied voltage? I would just use a 7805 reg. But that leads to another question, do you buy a reg or just buy a HE sensor? The problem is you still may need an op amp to get a clean signal from the HE, not a problem for me, i have some left over LM335's from from the last analogue thing i made, but it's a bit more of a problem for you Rob. Then of course you need to make voltage divider etc.
If you can hold off till after next week i will be back and should have the sensors and taco and can tell you what you will need to do.
The 7v from your plugpac will not really be 7v, unloaded it will be more like 10 or 12.

[nearnexus]

Sounds good to me Ueee.

I won't have the unit for some time, and there's no rush, so I'm quite happy to wait until you guys get yours sorted out and I will go the same/easiest route.

I don't want to risk stuffing the tacho up - maybe the optical sensor is not a safe way to go.

Rob

[toolman49]

G'Day Rob,
When you are calculating the gearing for your motor setup, a couple of things to consider are, whilst the motor is rated @ 4300 RPM, limiting it to something more conservative like maybe 2500 - 3000 RPM (easily done with KB controllers) you may extend your brush and commutator life considerably. While my motor is rated @ 1750 RPM it is set it to 1440 max, the same as the original AC motor. As I don't what your lathe is, I personally would be a little nervous about increasing the max spindle speed, will the bearings take it ? and how well balanced are your chucks ?, you may introduce vibration and harmonics which will negate any advantage of increased spindle speed.
Regards,
Martin

[simonl]

Hi Martin,

That's a good point and perhaps one that is often forgotten when we look at changing an existing design.

One thing I would say is just because your design brief includes an increase of max RPM to say 2500, doesn't mean it has to be used if you find it to be unstable or some other undesirable factors come into play. The spindle bearings should be taken into account and treated with utmost respect in relation to this as they can be expensive to replace and having to replace them because of excessive RPM would negate any advantages gained from the mod. Finding out the bearing manufacturers recommended maximum RPM for oil or grease lubrication should be easy to find and keeping under it (by maybe 10 - 15%) should be the go.

The premature wear of the motor brushes may just be an acceptable price to pay for the occasional luxury of increased max RPM available.

On motors, I have read that 3 phase induction motors are so much more efficient and smoother than their single phase counterparts but never really though much about it. The other day I had my 3 phase treadmill motor at full throttle of nearly 5000 RPM and it didn't even look like it was turning. Smooth as silk!

I now love 3 phase motors!

Simon

[nearnexus]

Hi all,

Thanks for the input.

The actual spindle speed is not going to be much higher as I am using the lower ratios to limit the speed - ie. running in the lower ratio pulleys. That way I get much better torque than winding back the motor RPM.

The only bearings that might get a workout are the intermediate pulley, but ball races should be good for less than 4300 rpm so I don't expect any issues.

My lathe is a much abused CQ9325 Chinese job - but she's served me well.

The point about throttling back the motor a bit is a good one. I will just have to see how much grunt the motor can transmit to the chuck. If it can pull a higher gear I will knock back the motor RPM.

Been rubbing back and painting the motor cradle/mount this morning.

Nice sunny day in Adelaide and it's looking good.

Moved on to trying to find somewhere to mount the big piece of aluminium plate I'm using as an auxilliary heat sink for the controller - 2 HP application has to have one.

Sounds simple, but these things never are, it's angle plate so I have to find somewhere that won't jag me as I go past.

Having a beer right now - a Chang beer in fact, which is not too bad :)

Cheers

Rob

[Stustoys]

couple of things to consider are, whilst the motor is rated @ 4300 RPM, limiting it to something more conservative like maybe 2500 - 3000 RPM (easily done with KB controllers) you may extend your brush and commutator life considerably.

But if you limit the rpm for a given power, the current will have to go up right?* So are you better off or worse off?

Stuart

*or am I over simplifying things?

[Ueee]

Depends on the controller stu, I don't know enough about the ones that that Martin has. I am probably going to add a pic or arduino to the mix to give real time feedback from the he sensor to the controller.

[toolman49]

G'Day Stuart,
The KB controllers have inbuilt current limiting, from experience in industry I found that limiting to about 75% of max speed (when the customer would allow it) increased brush life dramatically.
Ueee,
I don't know which controller you were thinking of using, but the KB controllers have tacho feedback built in as standard.
Regards,
Martin

[Ueee]

Hi Martin,
I was getting one of the KBIC's that Rob is getting from the states. I have found 2 donor treadmills so far but both have been 3 phase, not DC:~ Old treadmills don't seem to be quite as common here as in Melbourne (the place not the photo:D)
Do the KB's regulate on back EMF? I presume they are PWM controllers? The older smaller DC controllers i have used with back EMF never seemed as good as a controller with an actual sensor.

Of course the other crazy thing that has crept into my mind is putting a slide pot on the cross slide and hooking that up to the main speed control pot. Then the speed can be set for a given diameter and the slide pot would compensate for the dia getting smaller as you turn or even speed the lathe up slowly as you face or part........

[simonl]

Of course the other crazy thing that has crept into my mind is putting a slide pot on the cross slide and hooking that up to the main speed control pot. Then the speed can be set for a given diameter and the slide pot would compensate for the dia getting smaller as you turn or even speed the lathe up slowly as you face or part........

Now that's what I call feedback baby!

Then, lets go one step further. If you had a DRO you could take the signal from the Crosslide axis, feed it into a PIC circuit and then tell the PWM circuit how fast to go! As the DRO changes, it changes the speed accordingly, keeping constant surface speed as in your idea.

Nice to theorise, isn't it?!

Simon

[nearnexus]

"Of course the other crazy thing that has crept into my mind is putting a slide pot on the cross slide and hooking that up to the main speed control pot. Then the speed can be set for a given diameter and the slide pot would compensate for the dia getting smaller as you turn or even speed the lathe up slowly as you face or part........"

You blokes are something else :)

I just want my tacho to work.

BTW I priced getting the HP resistors in from the States for the KBE controllers, but no go, the postage is a killer. Better off getting them from CBC at about $10 each.

Rob

[simonl]

I have found 2 donor treadmills so far but both have been 3 phase, not DC:~


While I like the idea of using my 3 phase treadmill motor and the dedicated motor controller that drives it, I'm finding this to be very challenging. Breaking into the circuit to provide my own speed control is not as easy as I first thought. I'm not too keen to gaffer tape the treadmill to the lathe either or having to select 5 Km/h in order to get 1000 RPM!

Worst case senario, I keep the motor and buy a $150 VFD. That's a last resort though as it kills me to throw perfectly good working stuff out and the idea of using the treadmill circuitry to run the motor with an external POT is still my intent! It's killing me and doing my head in though. I have just enough electronics knowledge to create a nagging frustration and not knowing what the whole picture is. I've spent much time looking at the input signal waveform on the CRO and saying to myself.... There can't possibly be information in that!

Simon

[toolman49]

Fellas,
This is getting out of hand.
Regards,
Martin

[Ueee]

I've spent much time looking at the input signal waveform on the CRO and saying to myself.... There can't possibly be information in that!

Simon

He he, i know what you mean Simon, give me an analogue circuit anyday! Without knowing whats been flashed onto the processor's RAM it's near impossible to know what is going on. I just let the 2 i have found go as i have a small collection of 3 phase motors sitting around already, and i really don't need any more. Did i really just say that?:o

Mild steel, 40mm dia, so thats....6.5km/h.:;

[nearnexus]

I recon you should just run a belt to the lathe off the treadmill, and you could get a workout while your turning.

:)

Rob

[Ueee]

Fellas,
This is getting out of hand.
Regards,
Martin

Na, its just getting interesting....more interesting than the paperwork i'm supposed to be doing anyway......

[Steamwhisperer]

My head just exploded.

Phil

[simonl]

Hey, on a brighter note, I have just been looking through my collection of MEW and I found an article on EXACTLY what some of you are doing here. It's in FEB 2009 issue page 16 "Low-Cost High performance Digital Rev-Counter". Rob, the article uses what seems to be the same tacho module and the guy makes a 60 tooth optical disc to incorporate the use of the same optical sensor. He also gives the circuit diagram to interface the output to the tacho module and makes his own 5V supply to drive it. Pretty much exactly as we have been discussing but it all there on paper for you to read and get your head around.

Hope this helps.

Cheers,

Simon

[Ueee]

Interesting circuit Simon.
Not the way i would do it, with the use of a pre amp pull up resistor and post amp pull down resister, but i'm sure it works!

Exploding heads is just one of the services provided at the house of confuselectrics!
Its ok Phil, we know what we are doing:-......honest.....

[nearnexus]

Thanks Simon.

The only electronic circuit I ever built was a crystal set about 50 years ago.

And one of those graphic equaliser kits where you solder part A into holes A1 and A2.

They both worked - but it was a minor miracle of sorts.

Had a reasonable afternoon with my aluminum (as the yanks would say) heat sink. Found a place to put it and after much hunting around found an enclosure for the DC drive unit, two fuses, and power switch - an old XT power supply case - which is being suitably modified/resized with a disc cutter in my $20 air die grinder. Damn those things are good for small light stuff.

Here's a photo of the motor cradle and the half completed DC drive cover and heat sink.

You can see the section of power supply case I sliced off in the background, and also the piece I cut out of the base so that the DC drive controller can bolt directly to the heatsink - with a smear of thermal compound between the two.

Am quite pleased with the result so far.

The cradle still has to have four holes drilled and tapped into the end plate.

The heatsink is actually upside down in the photo. I will probably take another 5 mm off the XT case to move it back flush with the edge of the heatsink, if the DC drive will allow it. The control sits back from the front vent slots by about 5 mm to allow air flow through the case.

I'm using a 90 V KBI -240DS drive as a template until my 180 v drives arrive. Same chassis.


Rob

[jhovel]

Simon, would you mind publishing (or e-mailing me) the rest of the tacho article?
I've read what is there and would like to know more.
I've ordered one of the frequency counters a few days ago and would like to build a rev counter for my lathe too. I have a few infrared optical sensors out of a dismantled printer in my 'useful' box.... By the way, do these LED unit divide by 60 internally? It would be good to read rpm instead of rps :) or we need a 60 hole disk....
Edit: oops - just re-read the specs: you can set the mode and even custom dividers..... so any number of holes in the disk are possible.
This looks simple enough.
Cheers,
Joe

[toolman49]

Hey Fellas ,
As Rob says lets forget the DC motors, just connect the lathe to the treadmill with a flat belt and run like buggery.
See Yuz,
Martin

[simonl]

Hey Fellas ,
As Rob says lets forget the DC motors, just connect the lathe to the treadmill with a flat belt and run like buggery.
See Yuz,
Martin

Hey thats it! You may laugh at me now but when power bills get so high that we can't afford to switch on our machines, I will be able to go for a run and do a project! :U

Simon

[nearnexus]

Simon,

I saw these two Hall sensor circuits on Ebay - cheap.

Would either of these make it easy to connect up the tacho ?

New Hall Switch Sensor Module Smart Car Accessories JS1826 | eBay (http://www.ebay.com.au/itm/New-Hall-Switch-Sensor-Module-Smart-Car-Accessories-JS1826-/150813109684?pt=AU_B_I_Electrical_Test_Equipment&hash=item231d296db4)



Hall Sensor Module M44 Switch for Magnetic Field Detecting 16mA DC 0-15V | eBay (http://www.ebay.com.au/itm/Hall-Sensor-Module-M44-Switch-Magnetic-Field-Detecting-16mA-DC-0-15V-/130566462673?pt=AU_B_I_Electrical_Test_Equipment&hash=item1e665e1cd1)

Rob

[Ueee]

Either looks like it should work Rob.
My tacho and he sensors turned up today. Just a shame I'm 600kms away......

[simonl]

Simon,

I saw these two Hall sensor circuits on Ebay - cheap.

Would either of these make it easy to connect up the tacho ?

New Hall Switch Sensor Module Smart Car Accessories JS1826 | eBay (http://www.ebay.com.au/itm/New-Hall-Switch-Sensor-Module-Smart-Car-Accessories-JS1826-/150813109684?pt=AU_B_I_Electrical_Test_Equipment&hash=item231d296db4)



Hall Sensor Module M44 Switch for Magnetic Field Detecting 16mA DC 0-15V | eBay (http://www.ebay.com.au/itm/Hall-Sensor-Module-M44-Switch-Magnetic-Field-Detecting-16mA-DC-0-15V-/130566462673?pt=AU_B_I_Electrical_Test_Equipment&hash=item1e665e1cd1)

Rob

As Ewan said. Either will work. Personally I'm not too familiar with the setup. Not sure how close the magnet would need to come for it to register a pulse. It would certainly be a more reliable setup than an optical sensor if used in an oily environment such as inside the gearbox of a mill/drill.

Simon