AcuRite 5-in-1 Weather Station Modification - Hack #1

Modifed 5-in-1 sensor.    I recently purchased an AcuRite weather station model 01035.  Upon installing the weather station I noticed a temperature spike problem in the early morning and late afternoon.  Research revealed that this was a common issue with AcuRite stations equipped with the 5-in-1 outdoor sensor unit particularly in southern US latitudes.  For about two months around the summer solstice when the sun is low on the horizon in early morning and late afternoon it can heat the casing of the weather station before the solar panel begins producing enough power to run the internal aspiration fan.  The result is that the temperature readings go 5-10 degrees Fahrenheit above the real air temperature and then once the fan starts running the temperature readings suddenly drop back to normal.  This produces a "spike" on the daily temperature chart.  AcuRite recognized this issue and offers an upgraded top section with dual solar panels that catch the sun lower on the horizon and reduce or prevent the "spike" problems.  This was a design improvement which will hopefully be made standard equipment on future AcuRite stations.

    I bought one of the dual panel upgrades and installed it on my station.  It did fix the temperature spike issue however I started to notice a more subtle temperature problem with the station.  When the bright south Alabama sunshine was bearing down during mid morning and mid afternoon hours, even with the fan running, I was getting a temperature reading about 2-3 degrees above what my other thermometers were seeing.  I compared my station to others in the area reporting to Weather Underground and quickly perceived a pattern, the AcuRite 5-in-1 stations seemed to be the hottest things on WU!  I also noted that during mid day, when the sun was high overhead, the apparent elevated readings were greatly reduced.  In my opinion this is possibly another small flaw in an otherwise excellent weather station.  More research and forum reading confirmed to me that I was not imagining things.  Indeed, others had reached similar conclusions.

    If you have read anything else on this website you know I like to "hardware hack" a little so I set out to improve my 5-in-1 sensor.  Before I go any further let me be clear on one thing.  Any modifications you find on this page will very probably VOID your warranty!  If are not comfortable with that fact then stop reading now.  My first idea was to shield the sides of the unit from infrared solar heat.  I bought some metalized Mylar tape and placed it on the sides.  You can see a little of the silver tape on in the photo above.  This had little effect on the solar heating problem but did block the RF signal the station was transmitting back to the main console!  I removed most of the metalized tape except for a few strategic pieces near the temperature sensor.  I also tried some non-metalized white reflective tape but I could not detect much improvement from it either.  The reflective tape idea was a failure.

Accurite circuit board

     My second hack came after I realized I now had a spare top section that had been replaced with the dual panel upgrade.  The solar powered fan motor has a small voltage regulator board.  The voltage regulator limits the motor voltage to 1.5V and consequently limits the motor speed.  A little research on the motor gave me limited confidence that the motor could operate at up to 5VDC.  Checking the solar panel input voltage I was getting about 2.3V.  Hmmm, what if I jump out the regulator and speed the fan up?!  So I did and it did increase the fan speed.  I reinstalled the modified single panel top section to evaluate it.  The "spikes" returned but my daytime temperatures came closer to being in line with other non 5-in-1 stations in the area and the mid-day temperatures were very close.  I was still noticing some elevated temperatures mid morning and evening even when the fan was running.  I removed the hacked panel and reinstalled the dual panel top section.  I considered this experiment a partial success.Modified panel from above.

     After thinking about it for a few days I decided to go with a plan to not only add extra solar panels but to position them so that they shaded the sides of the unit during the mid morning and afternoon hours.  Note the shadow cast by the panel in the first photo on this page.  I also liked the "souped up" fan speed so I would leave the defeated regulator board hacked.  Time for eBay!  I purchased two 3V-500MA  Mini Solar Panels 200mm x 55mm ( 7 3/4" x 2 1/8" ) x 2mm thick.  These are the epoxy encapsulated panels which will hopefully withstand the weather.  I also purchased some 1N5819 Schottky diodes which allow all three panels to be connected to the regulator board.  The diodes pass current from the illuminated panel(s) while blocking loss to the dark panel(s).  I made some mounting brackets out of thin 1/2 inch wide aluminum sheet metal and mounted the panels on the sides on the unit at about a 45 degree angle.  I call it a winged 3 panel upgrade!

Acurite schematic     The wiring hack for the panel requires that the original existing panel be disconnected from the regulator board.  The three panels are then wired in parallel with a diode in each positive lead.  The output from the diodes is then connected to the (+) input of the regulator board and the three negative terminals from the panels are connected to the (-) input.  I located the diodes and also joined the negative wires near the circuit board tucked in under the existing original solar panel.  Take care to solder all connections and insulate them.  To defeat the regulator, install a jumper from (+) solar input to (+) motor output as shown in the picture above.  Although I have had no issues with a simple jumper here it has come to my attention that this technique will cause the circuitry inside the regulator to draw more current.  If you decide to bypass the regulator it is probably better to lift the regulator ground lug or cut the board trace in addition to adding the jumper.  Removing the board completely is also an option but  I think the capacitors on the board may shunt some of the RF noise generated by the motor so I have elected to leave the board in place.

     The results:  Since 7/19/2014 - very good.  The shading idea works!  My temperatures are running in line all day and the motor has not burned up yet.  The larger panels provide so much excess capacity that the fan runs even when it is cloudy.  It starts running early in the morning and continues until late in the evening.  I suspect the higher speed might shorten the life of the motor so I ordered 5 of them on eBay for $10.00.  My total cost for the two panels, 20 diodes, and 5 spare motors, was around $30.00.

     If you want to look at the station charts on Weather Underground, click here.

 Random notes and thoughts:
I don't think jumping the regulator board will cause any permanent damage to the little regulator and should be reversible but I am not 100% sure.  I did test my unit by soldering one end and then using the jumper like a switch.  It has a noticeable effect on the fan speed and my regulator was undamaged after being jumped.  If you choose to leave the regulator in circuit and not jump it, recognize that it might overheat with the 3V panels installed.  I suspect they may be a little higher voltage than the original panel.  A "finger" test of the regulator temperature with the motor running in full sunlight for a few minutes would probably be advised.  If it gets uncomfortably hot to the touch, you are pushing it... I assume the engineers used the regulator mainly to keep down noise and protect the motor.  Perhaps there is some negative effect for increased air flow through the unit but I fail to see what it could be.  I figure the outside unit is too far away for me to hear and the motors are cheap so let 'er rip!
• I used some Loctite Stik'n Seal adhesive  to stick the backs of my solar panels to the aluminum brackets.  This is an outdoor waterproof adhesive which remains semi-flexible.   I don't know if this is a good choice, time will tell.  Note that I bent the tip ends of the aluminum so that it formed an edge support for the solar panel.
• If you are reading this and thinking the AcuRite station has to be hacked to be good, then you are mistaken.  I like the weather station and there are thousands of them in use around the country.  The dual panel upgrade is recommended if you live in the deep south as it corrects the only major issue I would consider a design flaw.  I like to tinker with gadgets and this one is worth trying to improve...
I used stainless steel screws and aluminum brackets.  This is an outdoor unit, keep it rust proof!
• I drilled an oil hole in the anemometer shaft housing and installed a stainless screw as a plug.  This is a feature of the newer dual panel unit that is not present on the original.
• The winged solar panel unit does not look bad installed on the weather station.  If you do a good job maybe nobody will notice that it wasn't made that way!
An idea for those not comfortable hacking up your gadgets but would like to experiment.  Make some plain (non metallic) side flaps about the same size as my solar panels and attach them to your 5-in-1 unit on a 45 degree angle.  There is no need to permanently attach the flaps (use tape) to begin with.  The flaps would provide an extra layer of shade like my solar panels do.  I have not tried this experiment but would be interested to know if it lowered the mid morning/afternoon temperature reading and by what amount.  Basically, leave your unit as manufactured electrically but add some shading to the sides.  A reversible mod. to test the shading theory.  If this works, a dual panel unit with side flaps would probably perform almost as good as my winged panel version.

 Modified panel bottom

     I hope you find this information useful.  As usual I end by noting the fact that  I am not an electrical engineer, just a hack tinkerer ham radio guy so take that into account when considering this modification.  If you damage your equipment or burn down the block trying to use something you find on this site, don't come crying to me.  Heck, how do you think my junk box gets supplied?  Enjoy!







AcuRite 5-in-1 Weather Station Hack #2 - Temperature Humidity Sensor Failure

    One cold damp night in January it happened.  Alarms went off on the weather station console.  It was the wind chill alarm which I had apparently never silenced.  The outside temperature had dropped to 18 degrees!  What the heck?  The real outside temperature was about 34.  I watched the console for a few minutes and observed temperature and humidity readings jumping all over the place.  I finally grabbed a flashlight and went outside to check the 5-N-1 unit.  It looked OK so I tapped on the side of it a few times and went back in the house to find the temperature reading correctly and stable again.

     Over the next couple of weeks, with every damp or rainy day, my temperature and humidity would go berserk.  I took the outside unit down and apart and inspected the sensor board which is located just above the grilled wind tunnel port on the bottom of the unit.  What I discovered was that the green coating on the circuit board traces had deteriorated and exposed the blackening copper below.  There was also a fair amount of insect residue on the board.  I used a small square of electrical tape to mask off the port in the top of the sensor chip.  Then I took some CRC electronic cleaner (the non lubricating type) and using a toothbrush carefully and gently sprayed and cleaned the board assemblies.  I say assemblies because there is a small daughter board containing the sensor mounted with a 4 pin header on the main connection board.  Everything looked good and was working so I put the station back in service.

    When the next rainy day arrived the wild temperature/humidity problem appeared again.  Once again  I used a small square of electrical tape to mask off the port in the top of the sensor chip,  but this time I went one step further.  After cleaning and drying the boards I used an old rag to shield the rest of the weather station and I then sprayed both sides of the board assembly with Rust-Oleum clear enamel.  After waiting about 10 minutes I gave it a second coat.  Then, leaving the electrical tape masking the chip in place, I let it dry for 24 hours.  I removed the tape from the sensor chip, reinstalled the station, and so far this has cured my sensor issue!

    Here is the theory:  Once the green coating rots off the circuit board moisture accumulating on the board shorts out the circuit traces.  Acurite used a Sensirion SHT21 sensor in my unit.  This appears to be an excellent sensor that is widely used.  It communicates with the MPU using the I2C digital protocol which means it is returning a binary number over a serial interface.  A little moisture to screw up the timing and voltage levels will produce crazy readings.  By reinsulating the cleaned and dried circuit board with the clear enamel one can prevent moisture and insects from shorting out the circuit traces.  I would like to reiterate something in bold red print, I used a small square of electrical tape to mask off the port in the top of the sensor chip.  I know, that is three times but this is important.  Chemical solvents and outgassing vapors from the cleaner or clear enamel will DESTROY your sensor if they get inside.  The sensor is most likely NOT your problem so take special care of it when handling the board.

     Is your board completely rotten or the sensor actually bad?   I checked and Acurite says they do not sell the sensor board as a repair part.  This disappoints me.  As an old ham radio guy I am accustomed to buying parts and pieces from manufacturers to repair equipment.  This is especially true when there is a high failure rate for a part.  If you are not a good hardware hacker a complete board failure will mean a return to the factory on the 5-N-1.  If you are a good hardware hacker then take heart that there are some SHT21 breakout boards available.  I am investigating some of these boards and may possibly do an update to this page if I am FORCED to change my sensor out in the future.  At this point in my research I note that the Acurite board uses no "pull-up" resistors so any substitute board probably needs to have those disabled.  I also note that the Acurite board pin out is (-)(+)(SCL)(SDA) whereas many breakout boards are (+)(-)(SCL)(SDA).  This would mean that the polarity would have to be reversed for the first 2 pins on the 4 pin header.  I have not found a "drop in" replacement board with the correct pin out, no pull-up resistors, and just the plain capacitor across the power leads but hacking one of the Chinese boards shouldn't be too difficult if and when the need arises...

UPDATE:  On Acurite's newer 5-N-1 models they have introduced a user replaceable sensor board.  I have reliable information that if you are handy with a soldering iron this board can be used with older units.  The new board features a 4 wire plug-in connector instead of the soldered on ribbon cable.  Users report that the wires on the new sensor can be removed and the ribbon cable soldered on to it or one can also install a compatible connector on the main board of the old unit.  If this is attempted, mark your ribbon cable before removal so you can match up the VSS, VDD, SCA, and SCL lines properly.  KUDOS to Acurite for improving the new version and making the board user replaceable!  There is also a thread about this procedure on the WX Forum.  There is also an illustrated post on how to wire in the new sensor on the Acurite Forum.

AcuRite 5-in-1 Weather Station Hack #2A - Short Battery Life Fix

     My original 5-in-1 sensor developed the dreaded battery eating disease.  It would discharge 4 AA batteries in about a month instead of the usual 2 years.  I couldn't isolate the problem so I retired it and bought a new 5-in-1 sensor.  After a year or so the new 5-in-1 sensor caught the disease!  I was ready to abandon Acurite and move on to another brand but started to do some research and discovered somewhere deep in a forum where a guy had taken some current measurements and narrowed the problem down to the temp/humidity board.  I repeated his tests and sure enough with the board unplugged my current drain dropped below 30 micro amps.  I changed the board (very easy since it plugs in on newer units) and it cured the disease.  So I bought another temp/humidity board and installed it in my original unit (which was a soldering job but it works well).  The current drain on it also fell back to normal!  I wish I could find the original posting and credit whoever solved this problem but I have had no luck so I just post it here for those who are tired of paying ransom to the Energizer Bunny every month.  If your 5-in-1 is eating batteries there is a darn good chance that replacing the temp/humidity board will cure it.  If you have a good meter and know how to use it you can test your current draw with and without the board plugged in before you order one.

     I hope you find this information useful.  As usual I end by noting the fact that  I am not an electrical engineer, just a hack tinkerer ham radio guy so take that into account when considering this modification.  If you damage your equipment or burn down the block trying to use something you find on this site, don't come crying to me.  Heck, how do you think my junk box gets supplied?  Enjoy!

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