Simple Embedded Solutions

1. What is the purpose of LISN? A line impedance stabilization network is a device used to measure conducted and radiated radio-frequency emission and susceptibility tests. as specified in various EMC test standards.  Some test standards are CISPR, FCC, ISO, EN, RTCA DO-160, and MIL-STD 461D. LISN is a low pass filter unit typically placed between AC or DC power source and EUT to create know impedance and to provide a radio frequency noise measurement port. 2.  What is Conducted Emissions Testing? Electronics devices create noise current (Electromagnetic energy) and a certain portion of it will be conducted onto the power supply cord.  In order to restrict the amount of interference  DUT can couple back onto a power supply . Test labs measure these emissions and verify that they comply with specified limits.  This helps to ensure that the local power supply remains relatively 'clean' and nearby devices won't be affected by the DUT . Conducted...

1. Which produces more noise? Linear Regulator or Switch-mode power supplies? Compare to Linear regulator, Switch-mode power supplies have more output noise. Let’s see Why Switch-mode power supply output has more noise. Linear regulators are simple voltage regulator circuits commonly used in electronics. it uses a closed feedback loop to bias a pass element to maintain a constant voltage across its output terminals.  Linear regulators are step-down converters, meaning that the output voltage will be always less than the input voltage. Functional block diagram of Linear Regulator A basic DC-DC converter takes the current and passes it through a high-frequency switching element, which turns the DC signal into an AC square wave signal. This wave is, then passes through another filter (LC) which turns it back into a DC signal of the required voltage. Due to the high frequency switching DC-DC converter always has some ripple voltage on the output. Functi...

To select a proper MOSFET in our design we should consider the following things. VDSS VGS Switching Speed Considerations for VDSS:  The drain-source voltage VDSS rating is important in selecting MOSFETs. Application of a voltage exceeding VDSS might result in the destruction of a MOSFET. It is necessary to choose MOSFETs with a VDSS sufficiently higher than the voltage at which they will actually be used.   High VDSS rated MOSFET's will have large on-state resistance, RDS(ON). A downside of using such MOSFETs is increased conduction loss. Generally, on-state resistance determines the upper limit of the drain current ID. Ensure that not only the loss calculated as ID 2×RDS(ON), the permissible power dissipation but also a temperature rise due to heating does not cause the device to exceed its operating temperature range. Considerations for VGS: The on-state resistance of MOSFETs is low when they operate in the linear region. Therefore, for ...

555 Timer  Monostable  operation: The LM555 timer acts as a “one-shot” pulse generator. The pulse beings when the LM555 timer receives a signal at the trigger input that falls below a 1/3 of the voltage supply. The width of the output pulse is determined by the time constant of an RC network. The output pulse ends when the voltage on the capacitor equals 2/3 of the supply voltage. The output pulse width can be extended or shortened depending on the application by adjusting the R and C values. In this mode of operation, the timer functions as a one-shot (Figure 1). The external capacitor is initially held discharged by a transistor inside the timer. Upon application of a negative trigger pulse of less than 1/3 VCC to pin 2, the flip-flop is set which releases the short circuit across the capacitor and drives the output high. The voltage across the capacitor then increases exponentially for a period of t = 1.1 RA C, at the end of which time the voltage equals 2/3 ...

PIC16F877A interfacing with MCP23008 + Proteus Simulation This post provides how to interface MCP23008 with the PIC16F877a microcontroller. T his code is written in C language using MPLAB X IDE V3.30 with the XC8 compiler.  You can download this code from the ' Downloads ' section at the bottom of this page. It is assumed that you know the basics of I2C communication. If you don't then please read this link before proceeding with  this article. Simulation Results : Figure1: Simulation Example code : Figure2: Example code  Downloads: This code was compiled in MPLAB X IDE v3.30 with XC8 V1.38 compiler and simulation was made in Proteus v8. To download code and Proteus simulation click here.

  PIC16F877A internal EEPROM Tutorial This post provides the internal EEPROM reading and writing  code for PIC16F877A microcontroller. As we know , PIC16F877A microcontroller has 256 bytes of built in EEPROM data space with an address range of 0x00 to 0xFF. This code is written in C language using MPLAB X IDE with XC8 compiler. It is assumed that you know how to blink an LED with PIC16F877A microcontroller. If you don't then please read  this page  first, before proceeding with this article. Circuit: Figure1: PIC16F877A internal EEPROM Tutorial Code The code for the main function is shown below. Figure 2: Pic16F877A Internal EEPROM code Downloads EEPROM code for PIC16F877A was compiled in MPLAB X IDE  with XC8 compiler and simulation was made in Proteus v7.10.  To download code and  Proteus  simulation Click here