Updated readme.md

readme.md

@@ -12,6 +12,7 @@ Updated! Now the μReflow Oven is PID control enabled!
 For previous version which is non-PID controlled, pls see the branch ```Adafruit-EZ-Make-Oven-alike```.
 
 This project is an improved and heavily modified version of [Adafruit EZ Make Oven](https://learn.adafruit.com/ez-make-oven?view=all).
+The original code of EZ Make Oven can be found [here](https://github.com/adafruit/Adafruit_Learning_System_Guides/tree/master/PyPortal_EZ_Make_Oven).
 
 ![](./pic/overview.jpg)
 
@@ -23,16 +24,16 @@ Instead of an oven, a heating plate can also be used.
 
 The GUI of this project is built with LittlevGL ([lv_binding_micropython][lv]) which is a very powerful and easy to use GUI library.
 LittlevGL already comes with drivers for ILI9341 TFT display and XPT2046 touch controller, this project takes the advantage
-of both to ease the user operation. 
+of both to ease the user operation.
 
 ![](./pic/screen.jpg)
 
 ### Bill of Materials
-* 1 x regular kitchen oven with 10-12L capacity, like [this][oven] OR a heater plate, like [this][plate].
+* 1 x regular kitchen oven with 10-12L capacity, like [this][oven], OR a heater plate, like [this][plate].
 * 1 x solid state relay rated at least 10A. Like [this][ssr] (the heater plate linked above already includes it).
 * 1 x passive piezo buzzer. Like [this][buzzer].
 * 1 x ILI9341 TFT display with on-board XPT2046 touch controller. Like [this][tft].
-* 1 x Thermocouple amplifier with K-thermocouple. So far, MAX31855 and MAX6675 are supported. [MAX31855][max31855] [MAX6675][max6675]
+* 1 x Thermocouple amplifier with K-thermocouple.  So far, MAX31855 and MAX6675 are supported. [MAX31855][max31855] [MAX6675][max6675]
 * 1 x AC-DC5v power supply to power the ESP32 dev board. Like [this][acdc].
 * 1 x ESP32 dev board.  Like [this][esp32].
 
@@ -51,18 +52,25 @@ on and off via the solid state relay.
 * Configuration is done by editing the ```config.json``` file.
 * Hardware wiring: edit the value of the key names ending with '_pins' to match your actual wiring.
 * The TFT screen and the touch controller share the same ```Clock```, ```Data In``` & ```Data Out``` pins.
-* The ACC pin of the TFT screen is for powering on the display. You cannot power the display from a GPIO pin directly.
+* The ACC pin is for switching power of the TFT screen. This pin is optional. If your display has an
+input to switch power (often labeled ACC), you may connect the designated GPIO directly to this pin.
+Alternatively, you could use a transistor to switch the power supply of the screen.
+It has been reported that the screen can even be powered directly from a GPIO pin, however note that
+an ESP32 GPIO pin can drive at most 50mA (according to specification) and a typical 2.8" screen will
+draw between 80mA and 250mA, so this method risks damaging your ESP32.
+Since this pin is optional, you may safely ignore it (simply wire the 3V3 pin of the screen to the
+3V3 output of the ESP32).
 * The ```active_low``` properties can be used to make a pin active low.
-* ```sampling_hz``` determines the update rate of the temp sensor and the PID controller.  The default setting ```5``` 
+* ```sampling_hz``` determines the update rate of the temp sensor and the PID controller.  The default setting ```5```
 means 5HZ which is 5 times per second.
 * ```temp_offset``` & ```pid``` parameters can be set in the settings of the GUI.
 * ```advanced_temp_tuning``` can only be changed by editing the ```config.json```.
-    * ```preheat_until``` (temperature in Celsius) is used to set a temperature below which the oven will always be on - it helps to 
+    * ```preheat_until``` (temperature in Celsius) is used to set a temperature below which the oven will always be on - it helps to
     heat up the oven as quickly as possible at the early stage.
     * ```previsioning```  (time in Second) is for the PID to look for the set temp X seconds ahead, as the reflow
     temperature profile is not constant but a changing curve, this parameter will make the PID more reactive.
     * ```overshoot_comp``` (temperature in Celsius) it helps reduce the overshoot.
-    
+
 ### FTP access
 * The above mentioned ```advanced_temp_tuning``` may need some trial and error.  To make the fine tuning
 process a bit easier, the ESP32 will create a WiFi access point named ```Reflower ftp://192.168.4.1```
@@ -71,11 +79,9 @@ process a bit easier, the ESP32 will create a WiFi access point named ```Reflowe
 
 ### Installation
 * All files are under ```MAIN``` folder.
-* After flashing the firmware, you need to edit ```config.json``` to change the GPIO pin numbers according 
+* After flashing the firmware, you need to edit ```config.json``` to change the GPIO pin numbers according
 to how you wiring your TFT display and other components.
 * Set sensor_type to either MAX31855 or MAX6675.
-* The ACC pin is for switching the power of the display. If not using a transistor to switch, you may
-safely ignore this pin (simply wire the display 3V3 to the 3V3 output of the ESP32)
 * Some solid state relays will not switch on with the little current supplied by an ESP32 GPIO pin.
 In this case you have to use a transistor between the GPIO pin and the SSR. You may need to configure
 the pin as active low then.
@@ -87,17 +93,17 @@ the pin as active low then.
 will reboot.
 * After calibration and reboot, the GUI will load, where you can select Solder Paste type from the
 drop-down menu, just choose the type you'll use, and the reflow temperature profile will show down below.
-* If your solder paste isn't there in the menu, you can build your own solder profile files.  Pls refer to: 
+* If your solder paste isn't there in the menu, you can build your own solder profile files.  Pls refer to:
 https://learn.adafruit.com/ez-make-oven?view=all#the-toaster-oven, under chapter "Solder Paste Profiles".
 The new solder profile json file should be put under folder ```profiles```.
 * All set and click "Start" button to start the reflow soldering procress.
-* If you wish to re-calibrate either the temperature curve or touch screen, click the 'Settings' button
+* If you wish to re-calibrate the touch screen, click the 'Settings' button
 on the screen, and choose from the popup window.  And follow the on-screen instruction.
 
 ### PID tuning tips
 * Firstly, set ```previsioning``` & ```overshoot_comp``` to ```0``` in ```config.json``` to avoid confusing behavior.
 * Set ```kp``` to a small value, e.g. ```0.1```, and ```kd``` to a large value, e.g. ```300```.  This helps to minimize
-overshooting during the early stage which is typically seen in 'preheat' and 'soak' stage.  Keep decreasing/increasing 
+overshooting during the early stage which is typically seen in 'preheat' and 'soak' stage.  Keep decreasing/increasing
 ```kp```/```kd``` value until minimum overshooting is observed.
 * With a small ```kp``` & a large ```kd```, it's very hard for the actual temp to reach the peak temp of the ideal reflow
 profile, this is when you need to tune the value of ```ki```.  Slowly increase ```ki``` until the actual peak temp gets
@@ -116,4 +122,4 @@ really close to the ideal profile.
 [max31855]:https://www.aliexpress.com/item/32878757344.html
 [max6675]:https://www.aliexpress.com/item/4000465204314.html
 [acdc]:https://www.aliexpress.com/item/32821770958.html
-[esp32]:https://www.aliexpress.com/item/32855652152.html
+[esp32]:https://www.aliexpress.com/item/32855652152.html