Tuesday, October 11, 2016

Isolated RS-232 Serial Port Interface to SBC

Subject: Help! - Date: Thursday, December 16, 2010, 4:40 PM
Hello delabs
I have question about one your project . The question is about the project RS232 with Opto-Isolation on schematics.dapj.com. I need this very much . Do i need to use max 232 or something else on uC side , or i connect directly on uc rxd/txd pins .I need this answer so much , im new in this . please help

Best Regards
Mail from SS (CC) - Russia

This was done when MAX232 was not invented yet. This interfaces with PC well. If you want to make a PC based datalogger with 80C31, then this gives a safe PC to 80C51 SBC Serial Link.

Suppose a Temperature sensor or a Heater Open up. If the High Voltage reaches the A/D and SBC. The PC will be next Victim.

The Affordability and Product Safety Aspects, Including Fire Hazards; made me use this, as any other solution would make product expensive. An Opto-coupler and well designed PCB can give more than 2 KV isolation.

The MAX232 does not have isolation, but look here Isolated RS-232 Transceivers. The MAX232 also generates a Higher Voltage level, like 10V for proper RS232.


The MAX3250 is a 3.0V to 5.5V powered, ±50V isolated EIA/TIA-232 and V.28/V.24 communications interface with high data-rate capabilities.

The circuit i have made is very old and you can interface any serial uC with PC. No other chip is needed. It is cumbersome to build it and get it working for many. I suggest use one of these chips from Maxim unless you want to Adventure like me.


Thursday, October 06, 2016

SCADA System - Project Idea

I am a student of Electronics and Instrumentation Branch from BP. I am doing my training at ..... where i have been assigned a project to implement SCADA System using Microcontroller.

Right now,i have a good knowledge of PSOC and AVR microcontrollers but since i am new to this technology,i am not getting how i should proceed for the project.i would be greatful to you if you can provide some information about the previous projects students have done in you organization regarding scada implementation.

from MG

A "SCADA System" may consist of a Human using a Computer with Special Software Overseeing a Process Control System made of many sensors, transmitters, autonomous controllers and actuators made of motor drives and heaters.

SCADA System has a Computer, sometimes Network, HMI, PLC Control Panel, Secondary Slave Instruments. Autonomous Process Control in Remote areas and Protection and Fallback Units.

SCADA System

SCADA – Supervisory Control and Data Acquisition

Some of these elements may send data to the computer which may Analyze and Indicate the condition of process or progress. The Human Operator can then fine tune the parameters of his system or study and record process cycles for quality and yield.

You discuss this with your mentor and then build a part of it, or implement a part of it in an existing system. A whole SCADA system is too big a project, but a simulated or demo software interface project can be made.
This will be posted comment on that post to continue. Any other doubt post as a comment, .


Monday, October 03, 2016

Ultrasonic distance measurement

The following was submitted on June 7th, 2007 at 01:47AM (PDT). message: sent me the ultrasonic distance meter circuit

Mail from MS

Design of an Ultrasonic Distance Meter

There are several ways to measure distance without contact. One way is to use ultrasonic waves at 40 kHz for distance measurement. Ultrasonic transducers measure the amount of time taken for a pulse of sound to travel to a particular surface and return as the reflected echo.

DIY Ultrasonic Rangefinder

The ultrasonic transducers used in rangefinders like the Parallax Ping typically operate at about 40 kHz, but the surplus transducers I purchased have a lower resonant frequency of 24.50khz +/- 0.25khz.

Ultrasonic Range & Imager.

This is the electronic schematic of the homebuilt SONAR. Only one piezoelectric tranducer is used for both tramsmit & receive. This transducer is switched from TX to RX via the four 4016 switches. A high gain amplifier stage & rectifier translates the received echoes into voltage pulses.

Ultrasonic Distance Measurement With the MSP430

Ultrasonic Distance Measurement With the MSP430

This application report describes a distance-measuring system based on ultrasonic sound utilizing the MSP430F413 ultralow-power microcontroller. The system transmits a burst of ultrasonic sound waves towards the subject and then receives the corresponding echo. The MSP430 integrated analog comparator Comparator_A is used to detect the arrival of the echo to the system.