ID-4001 Troubleshooting Tips
Preface
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.
Troubleshooting
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 29.00 (or 0.00), 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 "course" pressure adjustment. It is best to adjust this using a frequency
counter or oscilloscope measuring 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 "course"
adjustment is from below 150 Hz to well over 800 Hz. So you are 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 ½ 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 sensors are close to their 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 wind direction
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 the 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.
|
|
|
Temp |
|
Temp |
|
U201 (3) |
U201 (1) |
U201 (7) |
||
|
|
|
Sensor |
|
Sensor |
|
|
|
|
|
|
|
|
|
Black |
|
White |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
32 ( |
|
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,
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.
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 couple of
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. 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. 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 are a bit different for
the wind speed outputs. 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 a 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.
Finally – The Elusive “Latch-Up” Problem Fixed!
I have been trying to
identify the reason that some ID-4001’s will latch-up displaying -40 on both
temperature readings and display a 0 on the barometer (29.00 with our
replacement board). They can only be
reset by unplugging the unit and plugging it back in. When this happens, U201 will get very hot.
The answer is… U207 is a CMOS device that is used to switch
the analog inputs from indoor, outdoor, and barometer to the V to F circuit
made up of U202D and U203A. U207 is
powered from a resistor network, R213 – R215, and operates with a +7 and -7
supply. U202 is powered directly from
+15 and -15, so it’s possible for U202 to output a voltage that is beyond the
range of U207. When this happens, U207
(being a CMOS device) will latch up causing U201 to run very hot.
Normally the voltage range
of U202 is well within the range of the +7, -7 volts. However, if switch SW201 is noisy or dirty,
there is a brief time when switching SW201 where the input of U201 has no
connection. This causes U201 Pin 7 (or
8) to momentarily hit the +15 or -15 limit and causes the latch-up
problem.
The easiest solution is to
add 1 Meg Ohm resistors to both U201 Pin 3 and Pin 12 to ground. This allows U201 to stay centered around 0
volts when switching SW201. The addition
of these resistors do not affect the measurement as they only draw less than 1 uA from the circuit that is running about 1 mA. I have tried
this in several ID-4001’s and have found that it fixes
this problem 100%.
This big clue to this
particular problem is that U201 will get very hot when the display is reading
-40 and doesn’t move. It can only be
reset by unplugging the unit and plugging it back in.