RPMs

[fabricator]

So, how would one go about measuring RPMs of a turbine without a tachometer? I know this is possible by measuring frequency but have no idea of how to go about it.

[B529]

120 divided by number polls = rpm per hz.

EX: 120/12 (12 polls) =10 rpms per hz. Measuring two legs, 16.4 hz on your AC frequency meter, 164 rpm

[kurt]

normally trying to measure hz with a meter with the turbine hooked to the battery will just lead to you being very confused because you are likely to get some very funny readings do to the way the rectifiers and battery distort the sine wave. that is the common result anyway.

[B529]

I have found this method to be very accurate and consistent, measuring any two of the three legs, obviously before the rectifier.

Has worked well for me when adjusting spring packs/rpms on Proven turbines I've installed.

[freejuice]

Hi Fabricator,
 When I think of electrical/electronics combined with math my head hurts so I did this:
http://cgi.ebay.com/LCD-Digital-Laser-Photo-Tachometer-RPM-Meter-Tach-Tacho-/250542664799?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item3a5581ac5f
 
 It actually works pretty darn good too!
 All the best,
 Gavin

[fabricator]

Yeah I've got one of those, but I don't wanna have to climb the tower to check the rpms.

[freejuice]

Oh! I see what you are up to! Cant blame you...maybe I do need to embrace math.

[fabricator]

You go right ahead, but you can count me out on that, I'm gonna do everything in my power to get around it.

[TomW]

You go right ahead, but you can count me out on that, I'm gonna do everything in my power to get around it.

Fab;

Well, wait til you run into the version of math where 1+1=11 !  Or one of the versions that uses letters.

Tom

[FishbonzWV]

DoubleU,

I see you flunked math class.
1 + 1 = 0
1 + 1 + 1 = 11   

[dlenox]

Fisbonz,

Actually it's  1 + 1 = 10 (not 0, you forgot to do the carry)

Dan Lenox

[FishbonzWV]

Yeh,
I was going to edit, but you beat me to it.

[fabricator]

You go right ahead, but you can count me out on that, I'm gonna do everything in my power to get around it.

Fab;

Well, wait til you run into the version of math where 1+1=11 !  Or one of the versions that uses letters.

Tom

Well, see, that makes perfect sense to me, a one plus another one equals two ones.

[zap]

You might want to try a bike speedometer.  I think I've tried mine with about 15 feet of wire max.
I don't know the max rpm it will measure.

http://www.instructables.com/id/Tachometer-made-from-a-bicycle-speedometer-cycloc/

[DanG]

Has anyone tried to extend the laser diode / sensor assembly on a remote sensing digital tach to a remote location? If the attachment wires were shielded and all the exact same length I wonder if the timing events would really get skewed around?

[freejuice]

Has anyone tried to extend the laser diode / sensor assembly on a remote sensing digital tach to a remote location? If the attachment wires were shielded and all the exact same length I wonder if the timing events would really get skewed around?

Hey that reminds me! There are wireless tachometers out there...I think automotive folks use them!.....some of the electronic gurus lurking around on this board could probably convert one over! Heck they might even have them for other applications too, but since I'm electrically dysfunctional....I dont know

One thing I like about this board, you folks are always giving me a good "edumacashun"...I have never really thought of checking the rpm's while the generator was on the tower....nice angle.

[TomW]

Yeah, I buggered the binary it is 10. Typical of my math skill these days.

Sorry for the diversion.

Tom

[B529]

Not sure if you guys can apply this to a homebrew machine,  this is how I measured RPM's on an old DC Jacobs. Epoxied 16 neo's to a disc, wound some thin wire around a pencil for a coil. 120/16=7.5 rpms per hz, very accurate. From the terminal and attached to a strain relief, dropped down a short cord with a female plug. From there a long cord to the ground with a male end very loosely connected. Loosely because if it got twisted, it would simply unplug, it unplugged a few times until I got the governor springs adjusted for the rpm I wanted. Spun the generator loaded on the ground to establish rpms from an adapter off my truck hub until the brushes sparked.

[fabricator]

Well, one relatively inexpensive way to do it would be a regular old proximity sensor and a magnet on the rear rotor, and a digital tachometer, but, I'm not sure how long the leads can be, the readout unit powers the proximity sensor so I have no idea if 250 feet is too far.

[gizmo]

If you can tap into the AC before the rectifier, then this circuit will clean up the wild AC into a nice squarewave. I use it on my Piclog ( picaxe based windmill logger ), and it works reliably down to 20rpm.


Glenn

[BrianSmith]

I built one that connected at the front of the rectifier like above and it works good.  I added a display and an RPM speed alarm output that would alarm with a buzzer when the RPMs were too high as well as an analog out to hook it up to a logger in the future.  Connecting up to the rectifier keeps it from being on top the tower.

[Ungrounded Lightning Rod]

You go right ahead, but you can count me out on that, I'm gonna do everything in my power to get around it.

Fab;

Well, wait til you run into the version of math where 1+1=11 !  Or one of the versions that uses letters.

Tom

Well, see, that makes perfect sense to me, a one plus another one equals two ones.

It's called "unary".  All the positions have equal weight.  There are as many ones as the number you're counting.

You're probably used to using this with every fifth "1" at a diagonal crossing the previous four.

[fabricator]

I had a unary infection once, little sulfa prescription cleared it right up.

[defed]

i spliced a digital bike speedometer onto my davis anemometer and it works fine for giving me the speed.  the anemometer (and speedo) use reed switches.  it gives me mph based on a user configurable 'wheel' circumference.  i don't think it tells me actual rpm in any of the displays, but you could probably figure it out from the mph?  not sure if it helps any, but i saw mention of the bike speedo in an earlier post.

i checked one of the links previously posted and it describes a way to get the readout in mph to be 1/100th the rpm.

[scoraigwind]

There's a simple frequency-to-voltage circuit in my beating control circuit at this link:
http://www.scoraigwind.com/circuits/index.htm

Use a 2917 tachometer chip.  As for mathematics you could just turn it once per second and measure the output.  That would be 60 rpm, and you can scale it from there.

I recommend using a small transformer to isolate the input and get it to go below the negative of the battery.

[BrianSmith]

Here a picture of the RPM meter I built, now I just need a generator to run it on....    Anybody with a few generators lying around in their garage want to try it out?

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[kurt]

allot of cheap bicycle speedometers off eBay or online junk places have an rpm setting allot of people use them as cheap tachometers. 

[jarrod9155]

Here a picture of the RPM meter I built, now I just need a generator to run it on....    Anybody with a few generators lying around in their garage want to try it out?

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Ill try it out for you I have a 18 foot machine

[BrianSmith]

That would be great.  Shoot me an email with your mailing address and I will send you the unit to tryout and test. 

Please let me know if you run into any problems.

Here is a link describing the unit:  http://sites.google.com/site/rpmmeter/ 

I can walk you thru configuring it, but basically it only needs to be told how many magnetic poles are in the generator.

[fabricator]

I'd be interested in one also, looks like it would work good for triggering the solenoid for my air brake, are they for sale yet?

[BrianSmith]

I was wanting some real world testing of the unit before selling it.  I ran it on a arbitrary waveform generator with some noise for testing it, but I would like to have it run on some generators before selling it.  I have parts to build 2 more units if you would like to try one as well.

[fabricator]

I'd like to give one a try, I'm just getting the electrical controls board populated and I've been looking for something to run a relay to power up my air solenoid to turn my parking brake on.

[BrianSmith]

I built one more up and its programmed up so I will send you it tomorrow.  You can program in the RPM speed you want it to fire at and test it out.  You are probably going to want to set it for latching mode, so once it fires it stays fired.  Email me if you have any questions when you try to fire it up.  Thanks