Reduce power consumption modifying board to turn off sensors in deep-…

…sleep

Added temperature sensor module to correct for load-cell temperature drift
Added image of non-mirrored front of original board

README.md

@@ -9,6 +9,29 @@ This project started because I wanted a propane tank scale so I could track (and
 the propane tank running our gas fireplace.  This was made harder because I use 40lb tanks and many
 scales only support 20lb tanks.
 
+
+
+Recommended Modification Tools/Parts:
+
+Tools:
+* Tweasers
+* Soldering Iron
+* Hot Air Reflow gun (~600F)
+* Knife or rotary cutting tool (to cut/grind thru a PCB trace)
+
+Parts:
+* ESP8266 module (suggest D1 Mini)
+* DS18B20 Temperature Sensor
+* 4.7K Resistor (suggest 1/4 watt or smaller size)
+* Large value capacitor rated 5V or higher (junk bin, big one that fits - mine was 2200uF 25V)
+* Wire (~28 AWG) for connecting ESP8266 board
+* Wire (~22 AWG) for connecting large capacitor
+* Shrink-tubing or tape (to insulate connections at temperature sensor pins)
+
+
+
+Background:
+
 After trying many things unsuccessfully I determined that none of the off-the-shelf solutions did
 what I wanted, most requiring a phone-app and some (such as the Flame King scale) wanting
 additional purchases to enable different size tanks in the app.  Even if I purchased it, the
@@ -37,26 +60,41 @@ Armed with this knowledge, I could then tack off wires for the analog-input, LED
 power, and ground to connect the ESP8266.  With a bit of YAML programming I then had the
 ESPHome firmware sending raw values, and just had to calibrate it!
 
+Unfortuniately, the load cell output seems to vary by temperature.  This meant that I had to
+add in a temperature sensor so I could compensate for the temperature of the scale to get
+reasonably accurate readings.
+
+At the same time I was adding the temperature sensor, I also made a modification to the board
+cutting a power-trace and connecting the sensor-power rail back to the ESP8266 GPIO pin so
+that it can switch off the extra circuitry while in deep-sleep and improve battery life by
+approximately double.  There seemed to be an issue with the start-up sequence not letting
+power stabilize before attempting to detect the temperature sensor but this can be worked
+around by adding a short delay in the YAML boot code.
+
+An easy way to further increase the runtime would be putting a 2x D-cell holder under the
+middle of the tank stand and run wires up to the AA battery compartment.  It may also be
+possible to use a small solar cell and rechargable batteries to top-up the batteries and
+extend runtime as well.  Although I have not tried it, I believe there is also sufficient
+space that a micro-USB connector could be plugged into the ESP8266 and carefully routed out
+thru the battery compartment hole or by cutting a tiny notch in the cover plate to power from
+a mains USB adapter, but my appication is not near a mains outlet (remember, propane you want
+away from sources of ignition and away from the house to the extent practical for safety).
+
+
+
 In the process, I have learned a few things noteworthy:
 * The factory board has a voltage regulator that holds 3.3v from input range 1.75-3.35 volts.
-* Power consumption with the ESP8266 and stripped down PCB is ~4mA deep-sleep ~150-170mA active.
+* ~150-170mA Power consumption with the ESP8266 fully-active
+* ~4mA Power consumption with the ESP8266 deep-sleep and always-on stripped down PCB is
+* ~2mA Power consumption with the ESP8266 deep-sleep and modified to shut off sensor power
 * The ESP8266 introduces some instability in the 3.3v line affecting readings which results
   in a higher than intended reading, I don't know the voltage regulator specs.  Adding
   a large capacitor across the power rail where the ESP8266 taps off seems to help.
+* The load cell calibration drifts with temperature.  Results varied by 6-7lb over 30F.
 
-Battery life still needs improvement.  It ocurrs to me an easy "fix" to increase the
-runtime would be putting a 2x D-cell holder under the middle of the tank stand and run wires
-up to the AA battery compartment.  It may also be possible to use a small solar cell and
-rechargable batteries to top-up the batteries and extend runtime as well.  Although I have
-not tried it, I believe there is also sufficient space that a micro-USB connector could be
-plugged into the ESP8266 and carefully routed out thru the battery compartment hole or by
-cutting a tiny notch in the cover plate to power from a mains USB adapter, but my appication
-is not near a mains outlet (remember, propane you want away from sources of ignition and
-away from the house to the extent practical for safety).
 
 
-
-Files:
+GitHub Files:
 Board Pics - Front/Back scaled to identical size and flpped to match positionally.  You can
 display both files in a photo-viewer and "toggle" between them to follow traces between the
 sides on your computer monitor easily.
@@ -70,70 +108,140 @@ Board Pics - Original unmodified board, and close-up of microprocessor
 
 Example YAML file
 * example ESPHome - fireplace_propane.yaml
+* example Home Assistant package - propane_scale_fireplace.yaml
 
 Modification Pics - installation in housing
 * Capacitor Added.jpg
 * ESP8266 Connected.JPG
 * ESP8266 Fit in scale.JPG
 
 Modification Pics - Wiring Reference
-* (ppt slide 1) Load Cell Original Wiring.JPG
-* (ppt slide 2) Signal Tap Points.JPG
+* (ppt export) Slide 1 - Load Cell Original Wiring.JPG
+* (ppt export) Slide 2 - Bottom Signal and Power Tap Points.JPG
+* (ppt export) Slide 3 - Top Modification and Power Tap Points.JPG
+* (ppt export) Slide 4 - Pinouts.JPG
 * wiring.pptx
 
 
 
-Recommended Modification Tools/Supplies:
-
-* Tweasers
-* Soldering Iron
-* Hot Air Reflow gun (~600F)
-* Wire (~28 AWG) for connecting ESP8266 board
-* Wire (~22 AWG) for connecting large capacitor
-* ESP8266 module (suggest D1 Mini)
-* Large value capacitor rated 5V or higher (junk bin, big one that fits - mine was 2200uF 25V)
-
-
-
 The Modification Process:
 
 1. Take apart the Flame King scale (remove all the bottom screws - be careful not to loose
    the screws, battery door, or small rubber grey fake-button-plug thing)
 
 2. Remove the PCB (remove 2 screws, gently pry board out of place)
    NOTE: Mine was stuck/glued to one of the blue alignment pins.  Use care not to break
-	       the PCB and try not to bend the LED indicator too badly.
+         the PCB and try not to bend the LED indicator too badly.
 
 3. Optionally (but recommended) note the position of and desolder each wire to remove the PCB
+   NOTE: If you break a wire or lose track of where it goes, the load-cell factory wiring
+         diagram is in the file "Modification Pics/Slide 1 - Load Cell Original Wiring.JPG"
 
 4. Carefully remove (desolder or otherwise) the microprocessor from the PCB.  Use care not to
    damage traces or other SMD components.  I used tweasers and a hot-air reflow gun at 600F.
 
 5. Carefully remove (desolder or otherwise) the Bluetooth module from the PCB.  Use care not to
    damage traces or other SMD components.  I used tweasers and a hot-air reflow gun at 600F.
-	 NOTE: This is probably optional, but it is just wasting power if connected to the board.
-	       Another option would be identifying and disconnecting the power-pins and leave it.
+   NOTE: This is probably optional, but it is just wasting power if connected to the board.
+         Another option would be identifying and disconnecting the power-pins and leave it.
+
+6. Use a knife or other tool (I recommend a Dremel cutoff wheel to "grind" away) to cut thru
+   the PCB trace next to the internal slide-switch to isolate the sensor-power rail from the
+   always-on 3.3v regulated power rail.
 
-6. Use small wire, connect each of the power and signal wires to the ESP8266 board on the
+7. Use small wire, connect each of the power and signal wires to the ESP8266 board on the
    side that the components are populated on (where you removed the microcontroller).
 
-     Reference diagram: "Modification Pics/Signal Tap Points.JPG"
-     * Status LED to bottom of R17 near the removed U1 processor
-     * Analog scale output reading to the corner of C5 near near the corner of the PCB
-     * 3.3V power to P4 pin 1
+     Reference diagram: "Modification Pics/Slide 2 - Bottom Signal and Power Tap Points.JPG"
+     * 3.3V power from large tab of UR1 (to 3.3V rail of ESP8266)
+     * Status LED to bottom of R17 near the removed U1 processor (to ESP8266 GPIO)
+     * Analog scale reading at corner of C5 near near the corner of the PCB (to ESP8266 GPIO)
+     * Switched sensor power to P4 pin 1 (from ESP8266 GPIO)
      * Ground to P4 pin 3
 
-7. Use large wire, connect the power and ground wires.  I recommend tacking them to the
+     Reference diagram: "Slide 4 - Pinouts.JPG"
+     * 3.3V power rail
+     * Ground
+     * Jumper wake-timer GPIO to Reset for deep-sleep wakeup operation
+     * Connect GPIO pins to appropriate points on the board and sensors
+
+8. Use large wire, connect the power and ground wires.  I recommend tacking them to the
    opposite side of the P4 header (the side with the switches) and running them towards the
-	 LED indicator where they can drop into a large-ish space in the housing to the capacitor
+   LED indicator where they can drop into a large-ish space in the housing to the capacitor
+
+9. Use small wire, connect the DS18B20 temperature sensor.  I recommend tapping power off
+   where the large capacitor was connected, data-wire back to the ESP8266, and the pull-up
+   resistor soldered across the power/data pins of the DS18B20 itself seemed the easiest
+   way to solder everything free-hand.  Remember to use shrink-tubing or tape to insulate
+   the pins of the DS18B20 from shorting to each other or any other components.
+
+10. Program the ESP8266 with ESPHome if you have not already done so.
+
+11. Carefully reinstall the DS18B20 sensor, capacitor, PCB, and ESP8266 (see modification
+    photos for ideas) such that they are clear of all housing pertrusions.  I recommend
+    test-fitting cover plate before installing the screws.
+    NOTE: Since the WiFi module gets slightly warm, I suggest trying to place the
+          temperature sensor farther away, near the battery compartment.  I also used a
+          small piece of 1/4" thick insulation foam to hold the ESP8266 slightly away
+          from the adjacent load-cell foot, but this is optional.
+
+12. Test the scale for operation, ensure that the raw weight ADC value changes with
+    weight placed on the scale, and that the temperature sensor is detected and reports
+    a reasonable value for the temperature.  Note units in log are C not F.
+
+13. Reinstall the bottom cover (don't forget fake-button-plug-thing in the hole) and screws
+
+14. Calibrate your scale, see ESPHome guide for detals how to calibrate sensor filters
+    by modifying the YAML values based on debug log output.
+
+    a) At a steady temperature (such as room temperature), calibrate the weight sensor
+
+       1. Set the scale on it's feet but empty (no load sitting on it)
+
+       2. Power on and review logfile for "*CALIBRATE Weight ADC: adc_raw=" lines, this
+          will be the left-side value for your zero-calibration in the YAML
+
+       3. Place a large known weight (suggest 60-100lb) on the scale.  I used one of my
+          spare full 40lb propane tanks (~68 lb), and weighed it with a bathroom scale to
+          get the actual known weight.
+
+       4. Power on and review logfile for "*CALIBRATE Weight ADC: adc_raw=" lines, this
+          will be the left-side value for your large-weight-calibration in the YAML.
+          The right-side value is your measured known weight from step 3.
+
+       5. OTA update the ESP8266 firmware with your new YAML file to fix calibartion
+
+    b) With a constant known medium weight (say around 20lb), calibrate the temperature
+       correction factor.  You will need to do this in multiple temperatures, after
+       waiting for the scale to fully aclimate to the temperature so the internals are
+       all stabilized to the same temperatured.
+
+       1. Start at the same temperature you performed the part-A calibration.
+
+       2. Power on and review logfile for "*CALIBRATE Temp LB-Correction: temp_raw=" lines,
+          this will be the left-side value for your weight-calibration "zero compensation"
+
+       3. Allow the scale (and ideally the sample-weight) to cool down to a moderately
+          low temperature.  You can do this outdoors in winter, or using a fridge/freezer.
+          I recommend 20-30F or whatever is near your winter temperatures that you care
+          about having an accurate low-fuel reading at.  If you are using it for a summer
+          BBQ grill, you may wish to go the other direction and get a correction offset
+          at a high temperature such as 90-100F instead.
+
+       2. Power on and review logfile for "*CALIBRATE Temp LB-Correction: temp_raw=" lines,
+          this will be the left-side value for your weight-calibration "zero compensation"
+
+       4. Place the known weight on the scale
+
+       5. Power on and review logfile for "*CALIBRATE Temp LB-Correction: temp_raw=" lines,
+          this will be the left-side value for your calibration "cold/hot compensation".
 
-8. Program the ESP8266 with ESPHome if you have not already done so.
+       6. At the same time, also note logfile output for the reported weight reading from
+          the line "*CALIBRATE Weight [...] / output="
 
-9. Carefully reinstall the PCB, ESP8266, and capacitor (see modification photos for ideas)
-   such that they are clear of all housing pertrusions.  I recommend test-fitting cover
-	 plate before installing the screws.
+       7. Take the known-weight, subtract the output reading from step 6.  This is your
+          right-side value for the "cold/hot compensation" filter adjustment.
 
-10. Test the scale for operation, see ESPHome guide for how to calibrate load cell readings
+       8. OTA update the ESP8266 firmware with your new YAML file to fix calibartion
 
-11. Reinstall the bottom cover (don't forget fake-button-plug-thing in the hole) and screws