Author Topic: A decent tachometer  (Read 4259 times)

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OperaHouse

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A decent tachometer
« on: February 05, 2015, 09:57:35 AM »
I bought one of these 5 digit meters for a project unrelated to wind for $10.  It reads out RPM to one decimal point (assuming you stay under 10,000rpm) or it can be set up to read frequency.  Input is 0-30V or 30-300V selectable by an internal jumper and it has an optional software filter.   The readout can be corrected by a multiplier divider setup.  I have corrected the instructions to be readable.

http://www.ebay.com/itm/371227294288?_trksid=p2060778.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Frequency and RPM Speed Display Setup

    NOTE: Disconnect the input signal before setting when the input signal is High level voltage signal (300V)


    Open the back cover of the meter,

    Press "S2" button (right hand top corner facing the connector on bottom) to enter "SET" mode.
    A single number 1 will appear with rest of the digits blank.
    This indicates RPM with Filter, factory setting.
    If another mode is required, quickly press "S1" button (left hand top corner) to change display mode.
    Setup reverts to normal display in a short time, only 10 seconds.
    The options are as follows:

    "0" means Frequency display with filter ;

    "1" means RPM speed with filter;

    "2" means Frequency display without filter ;

    "3" means RPM speed without filter.

    10 seconds later, the meter will automatically return to the measurement mode, or power-off and restart.


    Divider/Multiplier Value Setup

    NOTE: Disconnect the input signal before entering setup when the input signal is High level voltage signal (300V)

     Open the back cover, press the "S1" button (left hand top corner) to enter the Sub-frequency Value Set interface,
    "S1" button is the shift key which flashes the digit to be changed. Keep pressing till desired digit flashes.
   
    "S2" button is the value plus key that increments the value of the flashing digit.
     The divider value must be set to 1-99999 or the number of pulses per revolution

     In the case of a distributor, one rotation of the distributor represents two rotations of the engine.
     The divisor can be set to a value from 0.0001-9.9999.  For a distributor a multiplier of 2 would be a divisor of 0.5000
     Press "S1" until the decimil point of 0.0000 flashes.  Pressing "S2" sets the decimal point. Then enter the appropriate
     value as indicated before. 
   
     After the set of the desired divider value via "S1" and "S2", wait 10 seconds and the meter will automatically return
     to the measurement mode.



     Divider Concept:

     The number of the pulses for one rotation. For example, a gear can make 20 pulses for one rotation , the divider value
     should be set to 20.


     High and Low voltage signal input switch

     NOTE: Disconnect the input signal before setting when the input signal is High level voltage signal (300V)

     The default set for this meter is the low voltage input (3-30V), if you need high-voltage input(30-300V), you need
     to open the back cover and remore the black short jumer from the "L" pins (left bottom).

     Failure to remove the jumper and input the high voltage directly will damage the meter if the low voltage short jumper
     is not removed. We are not responsibility for this damage. Please be careful!!
 
     Input Pins:

     1: SIGNAL INPUT (YELLOW)
     
     2: SINGNAL GND  (BLUE)
     
     3: NC
     
     4: INPUT VOLTAGE "-" : GND  (BLACK)

     5: INPUT VOLTAGE  "+" : VCC (RED)

« Last Edit: February 05, 2015, 10:03:55 AM by OperaHouse »

Frank S

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Re: A decent tachometer
« Reply #1 on: February 05, 2015, 10:21:13 AM »
Thanks I had been needing something like that so I ordered 2 I figure that I will mess 1 up somehow LOL
I live so far outside of the box, when I die they will stretch my carcass over the coffin

kitestrings

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Re: A decent tachometer
« Reply #2 on: February 05, 2015, 03:51:23 PM »
The price is definitely right.  How's the apparent quality?

Generally I prefer analog meters for rpm, but I guess it depends a bit on the application.  ~ks
« Last Edit: February 05, 2015, 03:57:59 PM by kitestrings »

gww

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Re: A decent tachometer
« Reply #3 on: February 05, 2015, 05:17:42 PM »
Is this wired like a doc watson with a shunt?
Thanks
gww

OperaHouse

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Re: A decent tachometer
« Reply #4 on: February 06, 2015, 10:12:15 AM »
Input power 12-24V nominal is diode protected against reversal to a 78L05 regulator and the draw is about 20ma.   I generally like to isolate instruments from power so a 100 ohm resistor would provide spike protection and eliminate the need for a fuse.  Processor is a Microchip 16F886.

gww

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Re: A decent tachometer
« Reply #5 on: February 06, 2015, 10:49:16 AM »
Operahouse
I am not even well versed enough in curcuitry to understand any part of your post but the word diode.
Is there a clear wiring diagram sent with the circuit?
Thanks
gww

kitestrings

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Re: A decent tachometer
« Reply #6 on: February 06, 2015, 11:31:47 AM »
Quote
How's the apparent quality?

I'm wondering if it feels like a discount DC appliance from JC Wh#, or Harbor%, looks like it might hold up, or are you considering the money-back offer?

Frank S

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Re: A decent tachometer
« Reply #7 on: February 06, 2015, 11:55:59 AM »
GWW; I'm also not the sharpest nail in the box when it comes to electronics actually one of the dullest LOL
 that was why I copied OperaHouse's
 instructions and saved them   maybe with his instructions and the ones that should come with the unit I can figure out how not to let out the magic smoke when I connect one
I live so far outside of the box, when I die they will stretch my carcass over the coffin

midwoud1

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Re: A decent tachometer
« Reply #8 on: February 06, 2015, 02:44:23 PM »
Simple circuit for a tachometer. with: LM 2917
Analog or digital display.
It's in most of our cars today.
Suitable for small windturbines.
FB. Mw

OperaHouse

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Re: A decent tachometer
« Reply #9 on: February 06, 2015, 04:20:47 PM »
Like most of the things sent from China, there are no instructions.  They at least had instructions in the listings though they were not clear.  It took hitting the buttons a few times to figure what they were talking about.  For that reason I posted the the corrected instruction set.  I use fieldlines as my CLOUD.  If my laptop ever gets held for ransome, I can come back here and find the info.  Wiring is pretty foolproof.  Power is clearly marked on the back of the unit.  I would use a three wire hookup pins 1, 2 & 5 to avoid mixing up the signal ground.  It is reverse voltage protected and that greatly reduces the the chance of smoke.  I don't see any quality issues.

I just installed this today and used the 100 ohm in series with the 12V power, a good way to protect the unit.   I initially hooked it up to a magnetic reluctance sensor with sine wave output.  This had trouble at low speeds < 50rpm.  Understandable since this was a half volt sensor if I remember right.  That was just to give a quick demo.  I then installed a hall sensor and a magnet giving a 12V pulse.  Speed indication was rock solid and stayed within 1 RPM .   I think if I had a mill I would use a resistor with a5-15V zener to square off the signal and avoid any ringing that might happen with the mills rectifiers.

gww

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Re: A decent tachometer
« Reply #10 on: February 06, 2015, 06:26:34 PM »
Frank
I am with you on the copy and keep.  I don't know if I am going to order or not.  I have always wanted to know the rpm so I could see what my blades where doing but so far I have to take wind from weather stations that are all ten or more miles away and I can find no relationship to what is really going on with my turbines although when they say gust of 30 to 40 mph I always do well. 

Operahouse
I do thank you for the heads up.
gww

kitestrings

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Re: A decent tachometer
« Reply #11 on: February 06, 2015, 08:49:36 PM »
Quote
I have always wanted to know the rpm so I could see what my blades

I find that I'm constantly looking at this for a quick status, especially at after dark.  We've been using one of these boards from Brian Smith, who used to visit occasionally  here:
https://sites.google.com/site/rpmmeter/

There are a number of similar circuits presented by Commanda, Hugh, others(?).  This is simple and doesn't require separate wiring - and twisted pair and grounded shielding and the like - as with a mag pick-up at the turbine.

Ours has a LED that I extended and popped through the panel cover below the meter.  It glows if there is any rpm, and increases in intensity as the wind picks up.