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.


Saturday, August 13, 2016

CFL Lamps and Simple Inverter

Kindly help me make one issue devoted to------ CFL Ballast Circuits----viz. circuits to drive a 5/7/9 / 11W....upto 18 watts CFL from a 6 volts / 12v DC battery, or Solar Panel,(or 220 volts AC Mains) Believe me, this is a crying need ,of the day, all over.

The market is flooded with poor Lanterns, that work for 2 to 4 months then they can't be repaired even. Some makes are either high-cost/high Quality, or low cost - low quality. Custom Ballast ICs coming nowadays are no use, because they are obsolete in 4 to 6 to 12 months..

Also, the circuit must have a (SMPS) power supply too, with overcharging * under voltage cutoff, as the CFL goes black, on being switched at low voltage.

mail from SRM

I can try to help you, Please Explain your need. Which way do you want me to help you.

CFL Lamps and Simple Inverter

A simple inverter for florescent lamps
This inverter is very easy to construct, reliable, and even powerful enough to light up a 15W florescent tube (if you cool your transistor well). The only hard-to-find piece of this baby is the so-called yellow inverter transformer

Oh no! Not Another CFL Inverter
This one’s a beauty. It will drive multiple CFLs without the need for heatsinks on the MOSFETs. Fit heatsinks and you can run even more, up to a total of 100W.

I can design with some SMPS type chips. Overcharging is only in Emergency Light Lamps. CFL's do not have this as they work on 230V. Make a more detailed specification. Then I can think more about it.


the problem is NOT that simple.............. problem is to RUN a CFL bulb, from a 6v/12v DC battery. Again, the problems are-----

1)Efficiency, of energy utilization, in the battery
2)Without using Custom LSIs(which go obsolete Unavailable in 6/12 months time and are replaced constantly ,by ever more sophisticated costlier models
3)Blackening of the ends of CFL, near electrodes
4)LIFE of CFL(supposedly--12000hours for European CFLs;8000hours for Advts;5000hours maybe ,reallife...
5)Simple Circuit, which can be easily repaired in the field, by non-technical people in village/small towns.
6)Low Cost--so, even the poorest person can buy use it
7)Fast Charging , of the Battery(out of 24 hours--likely to be used for 4/6/or 8 hours .So, it has to be charged in the balance of 24 hours...
8)Low Battery High Battery Cut-off; to prevent damage to battery CFL
9)Compliance with the Basic Ignition Data, furnished by CFL manufacturers.These are like----filament voltage,Ignition Voltage, Current etc

mail from SRM

Tuesday, August 09, 2016

Binary ASK modem - Power line Modem

Want hlp in dsigning of a binary ASK modem or Power Line Modem.

Mail from AM UK

Study these links ....
Amplitude-shift keying (ASK)

Amplitude-shift keying (ASK) is a form of amplitude modulation that represents digital data as variations in the amplitude of a carrier wave. In an ASK system, the binary symbol 1 is represented by transmitting a fixed-amplitude carrier wave and fixed frequency for a bit duration of T seconds. If the signal value is 1 then the carrier signal will be transmitted; otherwise, a signal value of 0 will be transmitted.

OFDM-Based Power Line Communication Modem

"The MAX2990 power line communication (PLC) baseband modem delivers a cost-effective, reliable, half-duplex asynchronous data communication over AC or DC power lines at speeds up to 100kbps. The MAX2990 is a highly integrated system-on-chip (SoC) that combines the physical (PHY) and media access control (MAC) layers using Maxim's 16-bit MAXQ microcontroller core. The MAX2990 utilizes OFDM modulation techniques to enable robust data communication using the same electrical network that supplies power to all other devices on the network."

LEDs Allow New Remote-Controlled Lighting Applications

LEDs Allow New Remote-Controlled Lighting Applications

PLC technology allows communication over a long range. New OFDM-based PLC technology, including emerging standards such as G3-PLC™, is simplifying integration of lighting control applications by providing noise immunity and interoperability.


Wednesday, August 03, 2016

Winding Insulation Resistance Measurement

I am working in power plant. we have a problem on one of gas generator. the problem is that low winding insulation resistance of generator rotor. it read 800 k ohm where the other generator read greater than 10 M ohm. at full speed, there is no Kv measurement. same time no standing alarm from excitation system. all equipment are indicated okay.

My question is that is the relation between low isolation resistance of generator rotor and Kv measurement?

Mail from - IB SA Arabia

There is no relation between insulation resistance and any other parameter of you system. Insulation Resistance depends on age, physical damage on windings, humidity, contamination, wear and tear.
Let me know where you are doing the KV measurement. If you are measuring leakage voltage due to insulation breakdown, you have to fix it. The relationship of parameters does not matter. Small leakages can be tackled with grounding, don't compromise on safety and quality.

Dana Tekno Crossmeg Insulation Tester

Dana Tekno Crossmeg Insulation Tester

It is possible you may be touching one of the probes when you measure insulation, that may be the 800K, Even if one finger touches the probe, the circuit is closed via earth and a low 1M measurement can be seen.

The rotor the chassis all need to be grounded, and insulation resistance has to be measured after all power connections or electrical connections are removed. The electrical terminations unit should float for proper measurement, especially when you have doubts. Tell me about your progress.


I did not get a reply later, but i may not have understood the question well. The question also lacks details. In HV breakdown measurements KV is applied, but it has to be done after disconnecting all points. Beyond a limit, HV testing becomes destructive. Leakage Monitoring and Earth Leakage Breakers can be used. Motor/Generator Protection Units too. Even an imbalance in the current or Three phase problems.

It is best to use a Insulation Tester to apply little above Normal Voltage and see leakage, if this is a routine quality check. Better still, have a current sensor on the earth line and use a data logger to keep a tab on the leakage levels, temperature and voltage of all motors and generators. Even sound/vibration sensors will be an advantage. Before these electrical equipment fail many symptoms can be caught by data logging and limit windows. An electronic instrument or Trip Circuit will operate or alert after a fault occurs. Data logging and analysis will warn of a possible Motor or Generator performance degradation. Symptoms Indicate problems, prevention better than cure. Data Recording, Graphs and preemptive measures better than Breakdown Repairs in the Night. Drop in efficiency is an indicator for maintenace, This also prevents mishaps and power wastage.

It is true some insulation faults will show up on vibration and high humidity levels. These have to be simulated. In operation testing has to be done with sensors and recorders for leakage current etc. not insulation resistance.

Learn more about Insulation testing
- delabs

Tuesday, July 12, 2016

Ultra Sound Sender Detecter Diagram

I am a University Physics technical staff member and I am searching a Diagram and full detals about Ultra sound detecter (Sender & receiver & Detecter). It must be arround (Detecting range ) 1.2 MHz. This is for the student practical activities.

Pl help me if you have any information. This will be a gratefull help to the students for their studings.

Mail from PBG Sri Lanka

See an earlier post - Ultrasonic distance measurement if i find more it will be added here Ultrasound Have a look at all links below, that might help

Ultrasonic Sound

"Sounds in the range 20-100kHz are commonly used for communication and navigation by bats, dolphins, and some other species. Much higher frequencies, in the range 1-20 MHz, are used for medical ultrasound."

Ultra Sound Sensor

4QD-TEC: Ultrasonics: remote control and Intruder detector - These ultrasonic circuits are all quite old: my notes date them at mid-70s so ... The last circuit is an ultrasonic preamp with a twin T feedback to make it ...

Schematics Depot (tm) - ultrasonic switch circuit - The ultrasonic receiver circuit uses an ultrasonic receiver transducer to sense ultrasonic signals. It also uses a two-stage amplifier, a rectifier stage, ...

Silicon Chip Online - Circuit Notebook - Besides being used as a Bat Detector, the circuit could also be used as a simple tool to indicate frequency, to find tyre punctures (which emit ultrasound), ...

Ultrasonic (Ultrasound) Electronic Circuits - Ultrasonic (Ultrasound) Circuits