Wind Speed Display - http://santiampassskipatrol.org/wx/weather12.htm
This unit displays wind speed in units of miles-per-hour.

The front panel basically has a numeric display and an On/Off switch. These are all the user normally ever sees or touches.

The display has five buttons which are used for configuring the display unit. These buttons are normally inaccessible when the enclosure is assembled with the window in place.

The back panel has connectors for power and the wind speed signal, and a fuse. Power uses a detachable IEC power cord, the same as used on desktop computers. The wind speed signal arrives via a CAT5 cable which looks like an internet cable, but is electrically incompatible with the network. We will try to use a distinctive (purple) color to identify the cable and the wall receptacle which provides the wind speed signal.


What's Important to Know?

A location which is ideal for measuring wind speed is virtually the same for that of a lightning rod: On top of a steel tower, on top of a hill, sticking way above surrounding terrain for miles in every direction. In fact, the wind speed sensor on top of Hoodoo Butte has taken damage from lightning on several occasions.

The wind speed displays could take lightning damage through any copper line that enters their box. The wind speed signal arrives on a CAT5 cable, which passes its signal through an opto-isolator with a 5000 Volt insulation rating before its signal touches the display unit. The power cord has no natural protection, so a manual On/Off switch has been provided. When "Off", the display unit's "Line" and "Neutral" power wires are both connected to the "Neutral" wire of the power cord. If the power system bumps, both power wires bump together.

So . . . Don't be shy in turning the unit "Off" to protect it from lightning damage.

  • If you are outside, and can hear thunder, that's a good time to turn it off.
  • If you are inside, and can hear thunder, that's a really good indication it should be turned-off.
  • If you will be away, and lightning activity may happen, it would be good to just leave it off.

    Turning the unit back ON takes as much effort as turning on a light bulb. All you have to do is hit the switch, and in a few seconds it should resume displaying readings.


    How this Whole Mess Works

    If you are curious, or are having trouble with the display, here's a top-to-bottom overview of how this display works.


    The Wind Speed Sensor

    The wind speed sensor is located on top of Hoodoo Butte. It's the thing on top of a tower that spins in the wind. (It should be the only thing up there that is spinning or even shaking in the wind.) The faster the wind, the faster it spins, so it's a transducer which converts wind speed into mechanical rotation.

    The relationship of wind speed to rotation rate is reasonably linear for speeds over about 3 miles-per-hour (MPH). The conversion factor for this sensor is 100 MPH / 850 RPM (revolutions-per-minute), or 14.167 RPS (revolutions-per-second).

    The wind speed sensor contains a Hall-effect sensor (Allegro L80 (** fill-in the part number **)) inside its rotor which is used to detect the motion of a permanent magnet which is attached to (and spins with) the rotor. This is a second tranducer, which converts one mechanical rotation of the rotor into one square wave electrical pulse which alternates between zero and twelve volts.


    The Wind Speed Signal

    The wind speed signal is a twelve volt square wave, 50% duty cycle, toggling at a rate which is linearly proportional to the wind speed. The speed information is contained in the timing of the square wave's rising and falling edges. It's easy to regenerate a square wave pulse, so circuit loading and noise do not degrade the speed information over long distances.

    Coming off the weather tower, the wind speed signal is buffered with a LM/NE555 timer (integrated circuit) and then sent down the hill on the Green Chair's control cable. It makes its way to the North Lodge communications bunker where a second buffer circuit then distributes the signal to the wind speed display units.


    The Wind Speed Buffer

    The wind speed buffer is located in the North Lodge's communications bunker. It amplifies the wind speed signal so that it does not get bogged-down driving several display units. The buffer can drive up to four display units.

    The wind speed buffer provides a separate output to each potential load, and is protected such that no number of display units, even if a dead short to ground, can either damage the buffer or prevent other display units from operating.

    Each of the four output ports (RJ-45 connectors for CAT5 cables) has its own blue-green LED indicator which flashes when there is a load at the end of the cable. It flashes because the same current it uses is also passing through the (remote) display unit. The flash rate is that of the wind speed signal, so for troubleshooting, if this light is flashing, the display unit should be connected and getting a good speed signal.

    The wind speed buffer is powered by a 12 Volt wall wart plugged into a duplex outlet on the box's front panel. Nothing else should be plugged into this outlet, and the fuse will blow if any significant load is added. (Fuse is 1/4" x 1 1/4", 1 Amp, slow or fast blow)


    The Wind Speed Display

    The wind speed display unit uses an Omega DPF701 "Ratemeter", which measures how much time elapses between two successive pulses, and converts that time (in seconds) to a rate (in pulses per second).

    The Ratemeter can "scale" its displayed reading, so instead of reporting something like "14.17" (pulses per second), it can instead display "100.0" (miles per hour). The scale factor to do this conversion is a multiplier of 7.059.


    Configuring the Ratemeter

    To start, you will need to open the enclosure and slide the window out of the way, so the ratemeter's front panel buttons can be accessed. Try not to get electrocuted if you operate the unit with the cover off. The window is useful for keeping dust out of the unit, so plan of putting it back when you are done. (It also keeps other prying fingers from re-programming your display unit.)

    Setting the ratemeter's configuration only needs to be done once, or every time it gets replaced.

    If you need to make changes, the "Set" and "ADV"ance buttons are used to change one display digit at a time. The last step after making any change should be to SAVE THE CHANGES. Otherwise, whatever changes you made may disappear the next time power is cycled.

    Checking the ratemeter's configuration uses the same button sequence as setting, except that changes to the settings are not made or stored. The following sequence was used to review the settings.

    Poke a Button / See on the Display / Notes
    "Menu" "Func" What function is this unit to perform?
    "Adv" "rate" -> It is configured to be a ratemeter
    "Menu" "scale" The multiplication or division scaling factors
    "Adv" "1n .sc" The multiplier (there may also be a divider, but we don't use that)
    "Adv" "7.05900" To convert pulses-per-second to miles-per-hour
    "Menu" "Offset" A fixed amount which could be added to the displayed value.
    "Adv" "0.00000" -> We add no offset
    "Menu" "dec pt" Position of decimal point
    "Adv" "FFFFF.F" -> Display readings with a resolution of 0.1 MPH
    "Menu" "Config" Never needed to set this
    "Menu" "noStor" -> Changes made will NOT BE STORED unless you specify otherwise
    "Set" "store" -> Changes WILL BE SAVED when you press "Menu" once more
    "Menu" "loaded" -> Changes HAVE BEEN SAVED


    Opening the wind speed display enclosure

    If you feel the need to take a look inside, a few more comments:

    The enclosure is home-made, so the top only fits on one way. To get inside, remove the four (to six) screws which attach the top and sides to the base. The unit should be upright (bottom side down) when the top is removed, to avoid surprises like the front window falling off.

    The screws use tapped holes in plastic, so don't over-tighten when re-assembling. That's one reason why there are more holes than needed to keep the top attached to the base. Some will probably eventually strip-out.

    As the top slides off, you will also see that the plastic window also slides out of place. That was intentional, as the window must be removed in order to get to the front panel buttons for checking (or setting) the ratemeter's configuration.

    When you re-assemble the cover, beware that the window can press too hard on the front panel buttons. If so, it will display (??? something like "mode d"). To fix, loosen the ratemeter hold-down clamps, back-off slightly from the window, and re-tighten the clamps. You may need to cycle power to resume normal operation.


    Troubleshooting

    Once the wind speed displays have been proven to work (and they have ;-), there may be the occasional trouble of a display unit "not working". The earlier top-to-bottom description of what's involved in making these units work now becomes relevent to finding the problem.

    Since the generation, transmission, and distribution of the wind speed signal is spread from the top to the bottom of the hill, a fault at any point could cause a problem. Like the advice of "Follow the Money", in this case find (or follow) the wind speed signal. What works? What doesn't? Where did the signal fail?

    There are wind speed displays at several places in the area. If some work, and others not, the units not working are probably suffering from the same problem. Displays, in order of remoteness from the wind speed sensor, are at:

    Consider:

    The Wind
    It's working if: The wind is blowing.
    It's not working if: The wind is calm.
    If the winds are calm even good display units will indicate "0.0". This usually doesn't last for long, and it "fixes" itself.

    Wind Speed Display
    It's working if: The wind speed display shows a number of 0.0 or greater.
    It's not working if: The wind speed display is dark, or it shows anything other than a number (which would probably be an error message). If the display continues to indicate "0.0" and you know that it's blowing on top of the hill.
    Possible problems: Loss of power (turned-off, blown fuse, unplugged, dead outlet). Loss of signal (the purple CAT5 cable is unplugged (at either end) or defective, opto-coupler or input port on the ratemeter is dead).

    Wind Speed Buffer
    It's working if: The blue-green lights associated with each cable going to a display unit are flashing.
    It's not working if: The blue-green lights are not flashing.
    Possible problems: Loss of power (wall wart unplugged or has died, fuse is blown). Loss of signal (from the wind speed sensor). Loss of a display (cable to, or presence of a display unit at the other end of its cable).

    Wind Speed Signal
    It's working if: The signal is toggling between 0 and 12 Volts
    It's not working if: The signal is steady at either 0 or 12 Volts
    Possible problems: Wind speed sensor is not creating a signal: LM555 buffer on weather station datalogger board (at Green Dispatch) is dead. Cabling system has an open circuit.

    Wind Speed Sensor
    It's working if: It's creating a wind speed signal.
    It's not working if: It's not spinning or generating the wind speed signal.
    Possible problems: Wind speed sensor's Hall Effect sensor is dead (usually due to lightning). Rotor is not turning (bearing is frozen, or sensor is encased in rime ice due to an early season storm and the heaters have not been turned on).


    Replacements Parts

    Related to the Wind Speed Display:

    Fuse (on the back panel) is a 1/4" diameter x 1 1/4" long "MDL" (glass cartidge) fuse. Rated for 1 Amp, preferrably "Slow-Blow" or time delay. The ratings are not critical, as the ratemeter actually should draw about 0.1 Amp at its rated 11.5 Watts. Jameco has these fuses..

    Opto-coupler - H11AA1 by Vishay or Fairchild. JameCo electronics carries it, it's pretty cheap. Hopefully it will die instead of the ratemeter input stage if a lightning strike gets into the wiring. For other than a direct hit, its 5000 Volt isolation rating should protect the ratemeter.

    The Omega DPF701 series ratemeter is being phased-out by in December 2018. Just saw that announcement on the Omega web page. Omega identified a replacement meter DPF20-HV (smaller, cheaper, lower power, ...). The replacement will probably work just fine, though with a bit of care we can probably avoid ever having to find out ... Unless another display unit needs to be built.


    History

    2018 09/08 - Installed two wind speed display units (in North Lodge & Maintenance Shop), so a "User's Manual" seemed necessary. This is it. Bill Freund
    2018 09/08 - URL: http://santiampassskipatrol.org/wx/weather12.htm
    2018 09/08 - First pass. Should be perfect except for spelling and content.
    2018 09/15 - Second pass. Added topics. It seems to be more coherent . . .
    2018 09/22 - Third pass. Added a couple pictures, two links, tweaked a few words. The content seems good. Troubleshooting comments are somewhat cryptic, but sometimes terse is better than tedious detail.