Weather Station Troubleshooting
The manual for the ID-4001 gives a pretty good explanation of how the unit functions in the section 'Circuit Description'. I recommend reading it, if you haven't done so already.Having worked on many of the ID-4001's and also having helped to design the replacement CPU adapter board, I've stumbled across several 'gotcha's'. It is my intent to try to document what I've found and hopefully save some of you some time.
Typically, if your unit is displaying all (or most) of the digits, it may not need a new processor. The display is multiplexed and requires the processor to be running in order to display more than one digit. If only one digit is displayed and it is exceptionally bright, then, odds are, you need a new processor. Next check the 50/60 Hz input pin to the Mostek CPU. This should show a nice square wave of the 'mains' frequency. If not, then either Q401 or that input pin on the CPU could be bad.
Check the power supply. If the unit is completely dead (no LED's at all), you probably don't have power somewhere.
If both indoor and outdoor temperatures read -40, and barometric pressure is 0.00 (or 29.00), then the V/F converter is probably not running. This is equivalent to reading all 0's by the CPU. All of the analog readings are converted to a frequency that can be read by the digital processor. The V/F converter is comprised of IC's U202, U203, and part of U207.
The V/F converter has a very wide range of operation and it is possible to move past the desired setting quickly on the Barometer adjustments. Take care when turning the 'coarse' pressure adjustment. It is best to adjust this using a frequency counter or oscilloscope measure pin 16 of the Atmel CPU using our 'Calibrate' function. The actual range used for the Barometer is 280 - 305 Hz. The range of the 'coarse' adjustment is from below 150 Hz to well over 800 Hz, so you ar trying to find a very small section of the adjustment. If you don't have those tools, then center the 'Fine' control by turning it over 20 turns in one direction, then back 10 turns. This should place it close to the center of adjustment. Next adjust the 'Coarse' control 1/2 turn until you get a reading of close to 30.00 on the Barometer display. You will have to wait for the ID-4001 to make its reading after each adjustment.
Make sure that both temperature sensors are connected. When either of the temperature sensors are missing, the analog signal from the missing sensor moves outside of the normal operating range. This can cause the analog switch (U207) to not be able to read one or more of the other inputs. This can throw off the calibration, or even make the unit stop working. This is a very common problem when working on the ID-4001. Even if you are only working on the Barometric pressure circuit, a missing temperature sensor can cause troubleshooting problems. If one of the temperature sensors is not working, this can also cause the analog switch to not function because the input from the bad temperature sensor may be outside the normal operating range. Check the table below to see if both temperature senosrs are close to thier normal operating range.
The wind direction function does not use the CPU. Remember this if you plan to use the RS-232 interface on our new board. You must connect the 4-bits of the wind direciton from the ID-4001 to the 4 pins on our board. The instructions included with the CPU board give more details on this. The wind direction can be fully operational even though the processor is dead. Wind speed does use the CPU and will not function if the CPU is bad.
Replacing
the Processor
Follow the
instructions included with the new CPU adapter board to replace your processor
with our new one. Remember to
remove the 3.579 crystal, static RAM (U206), and the bias diode D205. D205 should be replaced with a piece of
wire.
Calibration
One of the
nicest features of the new CPU adapter board is the addition of a 'Calibrate'
mode. Make certain that both
temperature sensors are connected and turn the unit on. You should see the time and temperature
displayed on the front panel.
Hold the
Clear button down until the time display reads CAL 1. You can now cycle between CAL0, CAL1,
and CAL2 by pressing the Clear button repeatedly. You will notice that only the
appropriate display is lit when the unit is in each of the calibrate modes. This can help to ensure you are
adjusting the right control during calibration.
Place
the unit in
Place the
unit in either CAL 1 or CAL 2 mode.
Submerse both of the temperature sensors in an ice/water bath and allow
them to stabilize in temperature.
With the Cal/Norm switch in the '
This should
complete the calibration of the analog portion of the ID-4001. Hold down the Clear button again until
the ID-4001 goes back into the normal operation mode.
The above
calibration steps do not work when the ID-4001 is using the old Mostek CPU. Our 'Calibration mode' will lock the
ID-4001 into reading only one specific analog signal at a time, so you will be
able to take the frequency measurement going to the CPU. Since the Mostek part did not have this
mode, constant switching between barometer, indoor temp and outdoor temp, causes
the frequency to change and the reading to be invalid.
The
following Voltage chart has been useful to me in troubleshooting the analog
temperature circuits in the ID-4001.
Black
Wire White
Wire U201
(3) U201
(1) U201 (7)
32
(Cal)
2.71 -4.26 2.71
2.71
-4.86
32
2.71
-4.26
0.36
0.36
-0.73
60
2.84
-4.14 0.52
0.52
-0.96
85
2.96
-4.01
0.68
0.68
-1.18
Alternate
Temperature Calibration
Sometimes
the 'Cal/Norm' switch will cause the ID-4001 to lock up reading -40 for both
temperatures and either 29.00 or 0.00 on the barometer. I have seen some of these switches so
bad that they will also cause the latch-up problem even when stationary in the
'Norm' position. Check this switch
if you are having analog to frequency problems.
To avoid
using this switch during calibration, use both a 'cold' and 'hot' source for
calibration. A bowl or glass of
mixed ice and water will give a constant 32 degrees. A second bowl or glass of water at about
100 degrees will provide the hot source.
Use a fairly good thermometer to monitor the 'hot'
source.
Leave the
switch in the 'Norm' position.
Place both temperature sensors in the 'cold' source and allow them to
stabilize for a few minutes. Then
adjust the 'Intercept' controls to a reading of 32 degrees F. Then place both temperature sensors in
the 'hot' source and again allow them to stabilize. Then adjust both 'slope' controls to
reach the temperature of the water.
These controls will interact with each other, so it will be necessary to go
back and forth a few times.
Can't get
either 'Intercept' or 'Slope' to calibrate
First see if
the problem is with the temperature probe or with the circuitry. Temporarily swap the temperature sensors
and see if that channel will now calibrate. If it does, the problem is probably with
the temperature sensor and not with the circuitry.
If it is not
possible to achieve calibration, you can try changing the values of R204
(Outdoor) or R221 (Indoor) up or down to reach calibration of the 'Intercept'
control. Changing R208 (Outdoor)
and R223 (Indoor) up or down, will affect the 'Slope' adjustment. In some cases, I have had to change
these resistors by as much as 5k Ohms.
If you have
replaced the temperature sensors with my replacements
The original
temperature sensors (single IC) did not draw quite as much current as the
discrete replacement solution that I offer for sale. The typical current consumption is
within the specification of the ID-4001, however the maximum value is
not. Normally these will work in
the application without any changes to the circuitry. In some cases, it is necessary to
provide additional current to the temperature sensor by changing the values of
R201 (Outdoor), R216 (Indoor), R202 (Outdoor) and R217 (Indoor). These should be changed in sets of
R201/R202 and/or R216/R217. I have
found that replacing the 9100 Ohms with a 4700 Ohms and replacing the 6200 Ohms
with a 2700 Ohms works in all cases.
If you have replaced the temperature sensors and can't get them to
calibrate, try this first. If you
still can't get it to calibrate, then go on to fiddling with the other resistors
as above (Can't get either 'Intercept' or 'Slope' to
calibrate).
Input
signals from Weather Boom
The LED's
are wired like typical Christmas Tree lights, in series. If one LED is open, then none of them
will be working. The voltage across
the Black/White wires should be around 8 Volts. If it is 15 Volts, then the circuit is
definitely open somewhere. This is
a current limited 15 Volt source.
The current should be limited to about 20 mA with LED's or 38 mA when
shorted. Simply place a mA-meter
across the two terminals and you should read about 38 mA. This means that the 15V supply and
current limiting resistor is good.
These are Infra-Red LED's and are not visible to the naked eye. If you view them using a camcorder or
digital camera, you should see them glowing.
The input
signals from the weather boom should range between .5 Volts (Logic Low) to over
2.0 Volts (Logic High). If the boom
is not sending these values to the ID-4001, then the LED's or photo-transistors
may be a problem. If you are not
quite reaching a 2.0 Volt level, then adjusting the LED and/or the
photo-transistor may help. Remove
the two boards from the wind sensor body and re-assemble the two boards facing
each other outside of the plastic, without the interrupter disk in the
middle. Make sure that each
LED/phototransistor pair are facing directly into each other. You may find by gently bending the LED and/or
phototransistor, you are able to achieve a 2.0 Volt or greater output. Be careful not to mechanically overstress
the parts or they may break.
Also note
that the wiring of the ID-4001 and ID-5001 booms is a bit different for the wind
speed outputs. The wind direction
wiring is exactly the same for both.
Make certain that you are using the correct boom.
If you have
purchased replacement LED's and/or photo-transistors from me, please note that
the 'smokey' colored parts are the photo-transistors and the lightly tinted
(yellow or pink) parts are the LED's.
It's best to not open the individual packages until you are ready to
install them.
If you find
that the encoder disk is scratched or rubbing on the LED's or photo-transistors,
you can touch up the black portion of the disk using dark model paint. Be sure to add the paint to the painted
side of the plastic disk. You can
also add an additional # 6 lock washer on each of the mounting spacers, to add
some extra space between the LED's and photo-transistors to keep them from
rubbing in the future. A rubbing
plastic disk may also be caused by bad bearings if the lock washer trick doesn't
work.
'Scratch' Test
For a quick
test to see if the wind speed is working. Remove the Green wire from the
wind speed sensor screw, then use a small jumper wire to jumper from the Blue
wire (+5 Volts) and 'scratch' the other end accross where the Green wire would
be connected. This 5 Volt noise should create a reading on the wind speed
indicator.
Replacement
'Dummy' Temperature Sensor
Many people
have asked me if there is a way to place a 'Dummy' temperature sensor on the
ID-4001. Here is a circuit that you
can use to replace the actual temperature sensor while working on the ID-4001 or
just to see if your problem is with the sensor or with the circuitry inside the
box. This uses a 10k Ohm linear
control with a 6.8 Volt Zener diode across the outside terminals. The white wire will go to
the outside terminal where the Anode of the Zener is connected. The black
wire will go to the other outside terminal (Cathode), and the Shield will
connect to the Wiper or center contact of the control. This represents
half of a bridge circuit.
This will look electrically like one of
the temperature sensors. Adjust the
control to get about 3.0 Volts on the Black wire. This will, of course, not respond to any
changes in temperature. Moving the
control slightly, should cause the temperature to change. You may want to use a 10-turn control,
since very little change in voltage will cause a change in the
reading.