Homemade tachometer?

[amiklic1]

I am looking for some diy tachometer plans or pictures to build one for my wind gen. Any suggestions where to start? I was wandering to use bycicle computer, as it uses reed contact ( one impulse per turn). It may be good.

[David HK]

I am looking for something similar. This is what I would like:-

Tachometer - options to use Reed switch, Hall effect sensor, opto interuptor.

Temperature & Humidity - Celcius and Fahrenheit.

Connections available for input from a anemometer located not far from turbine.

Monitoring of voltage.

Time and date.

RS 232 interface.

On board microprocessor with x amount of memory.

Possibly some auto actuator to force furling.

This must come one day for all those people who use wind turbines. A suitable modification would be useful for water turbines.

[sahlein]

Hi,

I would suggest looking at Allied Electronics.  They have everything you need to accomplish this.

I've been using their stuff for over 20 years to keep my manufacturing plants

running.

Forget reed switches.  There are dozens of better sensors out there.

Most industrial speed controls use either an optical encoder or an inductive

(Hall) sensor watching some kind of gear or a collar with magnets embedded

in it.

Many counters (tachometers) have an output that could actuate a furling system

or change the load for you to control prop speed.  Furling might be a better

approach since you would not be as prone to burn things up by trying to just

load the prop down.

Joe

[phil b]

Why not use something like this? Several good ideas here.

http://www.fieldlines.com/story/2005/6/20/153917/028

[Speo]

If you want a logging system, check this: http://70.31.91.225/wind/logger.html?caller=11

Reading the actions of a joystick can be useful for logging lots of stuff(ie: the pots inside could be replaced with thermistors to read temperature, 2 pots means outside temp and coilTemp...each button can read a reed switch, so you can read the generator using one button, thge anemometer using another button, other button for reset...

There is lots of room for improvement.

Speo

[BoneHead]

Buy a cheap but reliable calculator. Maybe $2 at a dollar store. Take the face off but remember which button is the equal sign. Attach two wires to the contacts where the equal sign is and attach a reed switch to the other end of the wires. Attach a magnet to whatever you're trying to get the rpm's for in a place where the reed switch can be mounted close enough for the passing magnet to set it off. Mount the reed switch.

Punch "1 + 1" into the calculator and have a 1 minute timer ready. Start the timer and the machine at the same time. After 1 minute, whatever number is on the calculator is your rpm's minus one.

You could do this for less than $4.

If you can't scrounge a reed switch, make it where a piece of wire or something on the object shorts the two from the calculator. Same thing as long as the wires get shorted on every rotation.

[Ungrounded Lightning Rod]

If you're rectifying it at the ground you also have access to the AC output.  Hang a frequency counter across it.

If you have a home computer (I assume you do since you're posting) you can make a frequency counter with a couple resistors, an opto-isolator (or a LED, photodiode, and piece of black heatshrink tubing) from radio shack, a serial- or parallel- port cable with the non-computer-end cut off, and a little software and soldering.

You can also use the opto-isolator hack to convert the voltage from the genny to something that will run a cheap bicycle speedometer.

[amiklic1]

Can you point me to some schematics about this? I have acces to ac voltage, and I was allready thinking of using the frequency to count rpm, but I'm not sure how to do this.

[asheets]

I used to build these things when I was a meteorologist.  Two ways I've done it:

1. An easter-egg anem. using reed switches.  Hook that puppy into an old VIC20 or Atari400 through the joystick trigger.  A short BASIC program will convert impulses per minute to wind speed (at the ends of the spectrum, the conversion becomes more logarithmic than linear, so be careful).
   
2. gut a old PC mouse and use the encoders to trigger a standard RS-232 or USB port.  Takes a bit more programming talent, though.
   

[Ungrounded Lightning Rod]

No but I can describe one:

LED and resistor in series, across one phase of the genny.  (Or two LEDs and the resistor all in series, one LED a visible type for monitoring and checking you got the resistor right, one the LED in the optoisolator - which might be an infrared type or encapsulated so you can't view it.)  Pick a resistance value so the LEDs are non-trivially illuminated at the lowest RPM you want to measure, aren't burning out at the highest - (or at the charging voltage.)  Easiest thing to do would be to pick the resistor you'd normally use to run an LED from the charging voltage.

If your speedo has a reed-switch sensor just hang the photodiode / phototransistor of the optoisoloator where the reed switch would go.  (If the speedo doesn't count when the mill spins you've got the wires swapped so switch 'em.)

If it's an inductive pickup you'll need to figure out how it's hooked up inside.  Start by just hooking the photo-whatsit up where the coil will go and spinning the mill up - switching and trying again if it doesn't count.  If it doesn't count in either direction, you'll need to look into what the input circuit is like:

If one side is hooked to one side of the battery (check with an ohmmeter - with the power OFF - after you've disconnected the coil) you can probably drive it by putting a hundred-K or so from the other side of the battery to the other input wire, then hanging the photodiode/phototransistor and proceeding as above.  If not we'll have to look into it more.  (It might have some op-amp circuit in there that needs some figuring out.)

How's that for starters?