wireless counter

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jdboy3020
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wireless counter

Post by jdboy3020 » Mon Sep 19, 2011 6:54 pm

My friend put up an air compressor/wind turbine and it would be very nice to have an electronic counter to count the rounds of the compressor to get an idea of the output. I can't put the sensor wires up through the pivot because the air hose runs through a swivel through the pivot. Is there any fairly inexpensive and easy way to get that data to the house wirelessly (500') ?
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jwax
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Re: wireless counter

Post by jwax » Mon Sep 19, 2011 8:06 pm

I'm not familiar with what an "air compressor/wind turbine" is.
What are you attempting to measure? RPM of the turbine?
Wouldn't you measure the output with a voltmeter and/or ammeter?
Also, what 'sensor" are you referring to?

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Externet
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Re: wireless counter

Post by Externet » Tue Sep 20, 2011 6:45 pm

Yes, very hard to understand this boy.
A reflective tape (or piece of mirror) on only one of the windmill blades (if that is what it is) will bounce a fixed mounted laser pointer to a phototransistor in the house giving 1 pulse per revolution. That would allow counting rpm/period/frequency.

Miguel
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jdboy3020
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Re: wireless counter

Post by jdboy3020 » Tue Sep 20, 2011 6:49 pm

An air compressor/wind turbine is an air compressor mounted on a tower with three blades attached so the wind can pump air, looks very similar to a small electric wind generator. It's a new product on the market made by an Amishman in ME under the brand name "Winpressor".Since on some days it runs all day and some days it doesn't run at all, my friend still runs his diesel powered air compressor as needed. Now the question comes up:How much air did the Winpressor pump today-last week-last month? translation "how much diesel did I not burn because of the Winpressor?". Since it isn't as easy to measure volume of air as it is electricity I came up with the idea of counting the total number of rounds the compressor makes in a month or year with a counter similar to this:http://www.alliedelec.com/search/produc ... KU=6200101If I understand it right all I would need is a magnet on the compressor shaft and a magnetic switch to send the pulses to the counter, which is where I ran into the problem of how to run the wires from the stationary counter on the ground to the magnetic switch. (the winpressor is mounted on a pivot on top of the tower so it can swivel 360 deg. into the wind) If anybody still has any questions I will try to answer them. Thanks for any help or ideas!
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Re: wireless counter

Post by Robert Reed » Tue Sep 20, 2011 8:51 pm

So you need an upper sensor that rotates with the fan assembly. The first thoughts that come to mind are slip ring connectors mounted to the rotator with fixed wipers to the support apparatus. This would require some machining on your part. The second would be radio transmission from the sensor assembly on the rotator using one of the many Tx chips on the market (4xx Mhz or 9xx Mhz). this would involve a matching receiver with proper demod on the pole. Either way, you would be in for a project.

jdboy3020
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Re: wireless counter

Post by jdboy3020 » Tue Sep 20, 2011 10:55 pm

I already had and discarded the slip ring idea because I figured it would be hard to keep good contact through them over time, especially with low voltage but maybe I'm wrong. Miguel's suggestion about reflective tape and a laser sounded intriguing but the blades don't stay in the same spot as the head pivots about the center. I would need a laser that shoots out a thin but wide beam instead of a small spot. I guess my question was if there are any wireless ICs that are plug and play for guys like me that don't have any experience with programming.
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Externet
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Re: wireless counter

Post by Externet » Wed Sep 21, 2011 6:53 am

Yes, that was a goof; not considered the rotation from wind direction changes, it discards the laser pointer bouncing.

If a magnet is attached somewhere to the spinning windmill or its shaft and a coil picks up its proximity every turn; it would produce both - electricity to power a tiny transmitter and pulse presence.
The laser pointer could still be used aiming home from the tower; would flash every turn, self powered by the magnet passing near the coil.

Receiving those flashes at home, a counter could be implemented.
Miguel
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haklesup
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Re: wireless counter

Post by haklesup » Wed Sep 21, 2011 6:09 pm

They should get a website if they hope to sell more. But I suppose the Amish don't think that way

As far as measuring RPM, you can probably do that with a bicycle style speedometer. Its just a magnet and a reed switch that closes once each time it passes. These usually don't output RPM but speed and distance are reported and these would be proportional to what you want. The distance would be particularly useful, by correlating that with pressure increases, you can make a rough estimate of how much air you stored. For example if 1 mile gets you 10PSI, the rest is probably linear.

I say probably linear because many pumps require more energy to spin when the back pressure in the storage tank is high (think vertical bike pump). I assume the manufacturer has at least partially solved that problem. I can see the turbine stalling when the tank is full if not.

BTW, there are wireless sensor models of bike computers. you may need to replace with a stronger magnet if you can't get the sensor as close as its dcesigned to operate on a bike. you don't want too heavy a magnet or it might off balance the turbine, you may need to put a counterbalance on each blade or at least opposite the magnet

Optical pickups will be plagued by problems with ambient light or interference by weather or dirt build up. Acoustic pickup would be hard to calibrate and reject ambient noise. Ultrasonic is a candidate. A rubber wheel touching the shaft can be coupled to an optical encoder, the advantage here is you will get more than one pulse per Rev allowing you to sense low speeds. Not sure if there is a surface to roll on though.

A magnetic pickup can be enhanced in several ways. Instead of using the n.o. reed switch which is directly closed by the magnet, you could use a coil of wire to sense the magnet as it passes by, this will create an electrical spike which can be sensed electronically.

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Re: wireless counter

Post by jdboy3020 » Wed Sep 21, 2011 7:34 pm

Thanks for all the reply's and ideas so far. The wireless bike computer is a good idea that I will have to think about. I'm not so interested about RPM as I am about counting total rounds but it would be an interesting side benefit. Here's my reasoning for counting the rounds: if for example a 13 HP gas engine is running the same size air compressor at 700 RPM and is burning 2 gal of gas per hour, a little arithmetic shows that once the counter says the windpressor has made 4200 rounds you just saved around 7 bucks.
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Re: wireless counter

Post by dyarker » Wed Sep 21, 2011 11:52 pm

You didn't say how many RPMs max you're expecting.

If you go magnet/coil pickup route, I suggest two magnets on the shaft. Keeps the shaft balanced to reduce vibration at higher RPMs, and slightly better resolution at low RPM. Divide by 2 later in software/firmware.

Cheers,
Dale Y

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Re: wireless counter

Post by jdboy3020 » Thu Sep 22, 2011 4:54 pm

If I would use a couple of rare earth magnets on the shaft and a coil to pick it up, do you guys think it would be possible to get enough power from that to transmit a "pulse" from an antenna to a receiver 100' away? The transmitter antenna could not be directional because the head rotates 360 deg. to face into the wind but the receiver antenna could be.
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haklesup
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Re: wireless counter

Post by haklesup » Thu Sep 22, 2011 6:21 pm

if for example a 13 HP gas engine is running the same size air compressor at 700 RPM and is burning 2 gal of gas per hour, a little arithmetic shows that once the counter says the windpressor has made 4200 rounds you just saved around 7 bucks.
Woah, you're thinking RPH? After 4200 Revs, you have matched 6 minutes of gas engine time or 1/10th of an hour and if gas costs $4/gal (Mid grade to high test in CA right now) you spend $8 per hour so you saved 80 cents right?

an 18" bike wheel is 113" in circumfrence. A mile is 5280 feet or 63360 inches. so you need 560 revs to go one mile. That compressor in the ballpark of 70MPH if it were powering a bike wheel. If the prop on the windpressor were of similar diameter you would need roughly 60 to 80MPH wind to equal the gas motor output. More given prop efficiency losses. (that was a very loose calculation, I took some liberties claiming the prop would rotate the same curcumference for a given linear movement of air and that's probably not accurate, things will actually be worse this is closer to best case I think)

Now maybe there are places on the coast of Maine where you get that but sure is not here.

A more paractcal calculation here would be how much air storage tanks can be filled overnight and how long can that run the shop in the morning before the gas needs to kick in. (did you say 13hp Diesel?)

Personally I wouldn't spend more than a $30 bike computer because the real estimation will come with experience. A calm day gets me this much shop run time and a stormy day gets me that much shop run time.

There are too many engineering uncertanties to come up with an estimate with any kind of believable accuracy. Since there seems to be little or no web reference to this product ( a few forums mention it but itself has no web page or specs) However, I doubt amishman reengineered the compressor to run more efficiently given the input available from a wind driven prop. Its more likely he just made a transmission to go between an already designed compressor and the prop shaft. The prop probably provides plenty of torque but unless its geared up, would take forever to spin the compressor enough.

jdboy3020
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Re: wireless counter

Post by jdboy3020 » Thu Sep 22, 2011 11:21 pm

sorry I meant 42000 rounds on the counter.

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Re: wireless counter

Post by gerty » Fri Sep 23, 2011 6:17 am

Another approach, put a hour meter on the diesel compressor.
The total number of hours worked - the hours on the diesel = the number of hours run from turbine.
Just my $.02 worth.

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Re: wireless counter

Post by Smoke_Maker » Fri Sep 23, 2011 5:00 pm

jdboy3020,


I am assuming that the compressor is in the top thats rotates, if so than the air line has a coupler that swivels. It's a shame the compressor is not stationary and the shaft comes down to turn the compressor.

Is the shaft to the compressor in the center of the head that rotates? if so then you can build a arm mounted to the base that will read the magnets on the shaft!!

If not, than would it be easer to just take a reading of the total revolutions once a week??
Richard Furniss
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