This module contains an ESP32 Wroom 32d chip.
Here is the schematics for this module.
ESP32 schematics
Year: 2022
How to interface potentiometer to ESP32 to read ADC Values
Here is the simple code to read the ADC value and show it in the serial monitor of Arduino ide.
const int Analog_channel_pin= 34;
int ADC_VALUE = 0;
float voltage_value = 0;
void setup()
{
Serial.begin(115200);
}
void loop()
{
ADC_VALUE = analogRead(Analog_channel_pin);
Serial.print("ADC VALUE = ");
Serial.println(ADC_VALUE);
delay(1000);
voltage_value = (ADC_VALUE * 3.3 ) / (4095);
Serial.print(" Voltage = ");
Serial.print(voltage_value);
Serial.println("volts");
delay(1000);
}
Blown LM358P due to transients
An LM358p is a dual opamp IC which I used in a single supply configuration. I drive the LM358 just shy of its absolute maximum voltage which is +30V. So I gave I supplied 28.8V (+-0.1V). It works flawless but the power supply is a Meanwell switching supply which introduces transient when plugging into the mains supply.
The transient arise when I was plugging in the AC wire to the mains. I used an anchor 6A 3-pin male plug for connection. It was at the brief moment when the transient arise.
The transient which arises apparently has enough power that it blew the epoxy off the silicon and it did with a loud bang.
Doing rough calculation at the moment this happened
Let’s say the transient is double the supply voltage of = 2 x 28.9 V= 57.8V
let’s say the current drawn by the IC is 40mA which is its absolute maximum.
power = voltage x current = 57.8V x 40mA = 2.312W
so for a brief moment, this 2W is radiated by the silicon chip. Which caused the heating up of the epoxy and generating enough expanding force which blew out like that.
but let’s take a more reasonable transient voltage(ISO 7637-2: 2011) of approximately 110V at a rise time of 0.5uS.
so power = 110V x 40mA = 4.4W .
FAKE BD139 NPN transistors
I have recently found out that there are FAKE transistors in the market. I have a built a circuit design and when I bought the transistor from the Lajpat rai market in Delhi; I assembled the circuit on a test bench for measurements. But I was surprised that the BD139 did not work with 10mA at 30V and they began overheating. They heat up so much that bubbles appear on the front epoxy and it cracked. I thought that maybe it was damaged so I replaced the whole circuit with a new transistor set. But they also didn’t hold and this time they burnt a resistor along with them. I saw flames engulfing the 1/4 Watt resistors.
So I again made the circuit using the minuscule BC546B. Which neither get warm nor went into thermal runaway.
on the BD139 it was marked that it was manufactured by NXP. And I then checked the NXP website and found out that the NXP closed its manufacturing of this transistor in 2001.
There are a lot of BD139 transistors circulating in the market. It is essential that you must buy from a good source.
How to generate custom fonts for LCD display
There are various tools to generate font style for LCD display.
- Write your own fonts style. But this is will become hectic if you have a larger font size.
- Software tool
- The Dot Factory by Eran Duchan
- GLCD Font Creator
I like “The Dot Factory” font creation tool. It is minimalistic and gets the job done.
Here is the link to the Github page for The Dot Factory https://github.com/pavius/the-dot-factory
STM32F429I-DISC1
Datasheet for stm32F429ZI https://www.st.com/en/microcontrollers-microprocessors/stm32f429zi.html
This board have a 2.4 Resistive touch TFT LCD. which uses the ILI9341 controller.
The touch screen which I got with this display is very bad. you have to press down on the screen before you power ON the device.
The microcontroller is based on the ARM CORTEX M4F which can be clocked up to 180MHz. This particular board has an 8Mbyte of SDRAM included which is basically useless with this screen. If you want to see the full potential you have to use the LTDC peripheral which when configured with DMA2D gives you a very powerful development board with multimedia capabilites.
STM32F746IGT6 – An ARM CORTEX M7 Based Microcontroller
It’s an ARM Cortex M7 based microcontroller which has a maximum clock speed of 216Mhz.
Well, it has a few peripherals which when combined with its CPU, makes it a very powerful controller.
Those peripherals are LTDC, SDRAM Controller.
It also has the usual set of peripherals from the ST. But these in particular makes it a very powerful microcontroller.
Do not connect microcontroller pins to the VGA monitor directly
I tried to generate VGA signal on stm32f103
I used two timers, the TIMER 2 generate the horizontal sync and then the second timer TIMER 3 is configured in gated slave mode which generates the vertical sync.
Then I used HAL_SPI_TRANSMIT_DMA function inside the timer 2 interrupt handler.
I in a hurried manner connected the video signal to the monitor directly. And that has burned the image onto the monitor.
I connected the green video signal directly from the stm32f103 to the VGA connector.
image is now burned in the monitor.
