Circuits FAQ

This is the Archive of Electronics Design related Question & Answers. Ask Questions at EE BBS FAQ. To get a project designed by delabs visit Design Service.

Search This Blog

Wednesday, November 16, 2016

Decade Digital Counter Module - LED and LCD

I'm looking for a source of decade counters and wonder if you can help? I don't want to build the counter, I want to buy a functioning counter module.

Do you have source suggestions?

Mail from SF USA On 1/1/2011 1:34 AM

Try These, some are kits, some ready modules.

delabs has a resource on counters -   Digital Timers Counters and Clocks

Easy way to build a counter since the 80s is using ICM7217.

4-Digit, Presettable, LED Up/Down Counter

4 Digit Counter Module - The counter module is supplied pre-assembled and tested and provides the building block for counter and timer circuits. 

The counter module may also be used as an accurate digital timer with the addition of a suitable timebase and gating circuit.

4017B Decade counter (5-stage Johnson counter) - Learn about the 4017 by building the DOCTRONICS Light Chaser Project:

Multifunction Counter-Timer Electronic Kit K8035 - Counter-timer K8035 is a multifunction electronic kit that is handy for all sorts of counting and timing applications. Counts up or down from your own pre-defined starting point. Counter-timer can count each time you press the onboard push buttons, or count externally supplied voltage pulses.

VM147 - Panel Counter MODULE - offers a very practical solution for counting parts, people, scorekeeping, etc.

LCD counter module 7016 6-digit - Snap-fit module with 4-digit LCD and its own power supply (not included). This counter module is therefore suited to PCB-mounting (snap-in frame can be removed) as well as front-panel mounting

Try Radio Shack ask for - LCD Counter Module - it may be expensive compared to above.

Tuesday, November 15, 2016

Three Phase AC SSR for 1 HP Motor

I need to build a three phase AC(in 120V)-AC(out 440V) solid state relay to turn on or off a small(1hp) three phase AC motor. Do you have any idea?

Can I use three MOC3043 and three TIC236E triacs of course with all opto LEDs in series?

Mail from FJP Brazil

See my SSR Circuits , Solid State Relays or SSR Choose a DC Control and AC Load SSR, That is what you seem to indicate.

1 hp = 745.699872 watts

Let triac have 10 A and 600V AC ratings, BTA12600 But now BTA12600 is obsolete, adapt to what is available in your country.

MOC3043 is fine, isolation must be good, take care. Use a Heatsink.
ON-OFF Control inputs can be parallel not series.

Here is a picture of a Solid State Contacter from Power IO

Three Phase AC SSR for 1 HP Motor

On this page you can see a 3 phase SSR i built. Three-Phase-SSR.


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 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. I have a project of designing a binary ASK modem, with a microphone as an input and a speaker as an output.

    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."

    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


    Sunday, July 10, 2016

    Logic Analyzer on Computer

    Title: Test circuit for Logic Analyzer - Message: I am a retired hobbyist. Source files needed.The following was submitted on March 8th, 2008 at 06:47AM (CST). Subject: delabs Schematic Source Request.  Circuit: del20006.pdf .
    Mail from JL USA

    Sorry for the late reply, Can you explain in detail your doubt or problem. Meanwhile Have a look at
    these circuits

    40MHz 32 Channel Logic Analyser It is a 32 Channel, 40Mhz, fully PC controlled TTL/CMOS logic analyser with internal/external triggering and trigger delay. Internal triggering is fully maskable (High/Low/Don't Care) on all 32 channels.

    FPGA Based Logic Analyzer The project includes the actual analyzer in VHDL (for Spartan 3 FPGA) and a PC Software for the end user. The design employs a FPGA board that can be obtained easily.

    Logic Analyzer on Computer

    MiniLA - logic analyzer SW & HW.
    MiniLA is a project of simple and cheap logic analyzer designed for amateur and semi-professional work.


    I am interested in obtaining a copy of the file "" referred to in the article. PC-Based Logic Analyzer (below). The link to the file is not available. The file contains the software for the circuit described.

    Reply from JL

    Thursday, July 07, 2016

    Understanding Transistor Power Dissipation

    I like your page about current source circuit basic design. However, I still have Little confuse of the power dissipation calculation.

    The max power dissipation of my circuit is 20.5V x 0.5A = 10.25W, but transistors I found are 2W power dissipation. But my input voltages is just varied from 18.0V to 20.5V only. Do you think the 2W power dissipation transistor is fine? Any help will be appreciated.

    Mail From MT

    When the Current source output is short circuited or connected to a low impedance load say 10 ohms, the full voltage of input 20V falls across the transistor but current is limited to 0.5A. which means the 2W transistor may Roast. The transistor when conducting, the watts is the volts across it and current thru it. Not your supply Voltage.

    Power Electronics & Solar Energy

    HeatSinks in Electronics

    Power Supplies Section

    Design in such a way there is no short circuit or a a power resistor in source. But then efficiency drops. The best way is to use a switching supply design or keep the input voltage across transistor to a minimum.


    Friday, June 10, 2016

    SSR Open Circuit Leakage Voltage

    hi been trying to use a dc ssr relay to switch 24 volt supply on and off for a unit i use that needs to see 0v or 24v but when the switch voltage is applied there is still 18v showing on the load side not zero ..does the ssr have to have a load on it to fully switch off and on from 0v to 24v ?

    Mail from PST in UK

    You are right you need a bleeder resistor of 10k or 100k to ensure the collector leakage current of SSR is bypassed to make you see a '0' when the SSR is off. If the SSR is working well, and no input or '0' control input then SSR output is high impedance and only a collector or diode leakage will hold the SSR output at the Full Voltage but it cannot drive any current. Hence a bleeder across output will show you a '0'. Use it if the bleeder does not cause any problems.

    Solid State Relays or SSR

    If you were driving a 5A Solenoid, then you would not see this problem. If you are driving a Solid State Load, such effects are natural. It is because the Solid State Load like a Electronic Circuit will draw current only on demand.

    These instruction is for a Normally Open Output, NO. A Normally Closed NC is vice versa. And also some Special SSRs may have sensitive inputs, So a low impedance '0v' at input has to be ensured.

    The Bleeder should bypass the leakage current, so one end of bleeder goes to SSR output and other end of bleeder goes to the ground or 0V point of your circuit which is controlled by SSR.


    They are called SSR as there are made of semiconductors and have no moving parts to wear out. They do generate heat depending on load and switching. Thyristors are used in most as they are rugged, mosfets and IGBT may also be used for various applications.

    Solid State Relays or SSR

     In this section you will find SSR designs and PCB layouts which you can study. These were made and sold  by me years ago. So the PCB layouts have gone thru some revisions and they worked quite well.

    Wednesday, June 01, 2016

    LM3914 meter for 25 V DC

    "I wish to assemble a bargraph display to indicate approximately 25volts dc.How many LM3914 I should cascade? How to calculate resistor value which is grounded from the junction of Pin 6 & 7 (Rhi &Ref.out)? Assuming i need to cascade 3 LM3914s,what is the method to cascade these ics? The display need not be precise or very bright. I hope you can help me out."

    Mains Voltage monitor using LM3914

    "I shall be very grateful. Can we do it in such a way that the first LM3914 displays 1-10 v & second 11-20v & the third 21-30v?"

    Thank you again - Mail from AD

    Reply from delabs

    Have a look at the TI application note which has many examples. Understanding this will help you make your own solution.

    LM3914 - Dot/Bar Display Driver

    20-Segment Meter with Mode Switch

    20-Segment Meter with Mode Switch

    Analog and 3-1/2 digital display

    Cascading is required if you want more resolution. Example for measuring 20V, you want to show in 1V per LED steps. It can withstand +/- 35 Volts input upper limit.

    The inbuilt reference is 1.2V use it as shown in the Typical Application. This also helps in setting the brightness of LED display. You may need to use external attenuators, buffers or precision  rectifiers to measure AC voltages or High Level DC voltages.

    Wednesday, May 04, 2016

    Long Duration Linear Sweep or Ramp Generator

    I hope you can help me with a circuit. Its a voltage sweep circuit that will sweep from 0v to10v in a 45 min time period, I'm using it for an input on a signal generator to control the output frequency.

    I have tried a constant current source charging a capacitor but it just didn't seem to be solid. If It can be done digitally would be great! I have been struggling to do this and its the last part of the piece for my project.

    Mail from CB in NA

    I have once answered a similar question. Ramp Generator Elex Quna.

    You need clock pulses driving a counter, which operate a digital potentiometer. Or any D-A convector - or R-2R circuit. Say you need 1-10V in 45 mts. You first figure how fine the ramp needs to be, like resolution of 100mV?

    The constant current may not work as the capacitor may leak and it may not be a perfect ramp. The cc ramp is good for 1 second or less.

    A staircase ladder ramp is best for you, define every step of ladder as say 10 or 100mV. A clock of 1 Sec is given to a counter, binary counts, and the digital output of counter goes to D/A Convertor.

    Another here with LTspice, install and launch  LTC6993-2 Demo Circuit to try.

     Pulse Staircase Ramp Generator
    "This design highlights the use of the LTC6993-2 and LT1490 to generate a pulse staircase ramp that is re-triggerable. "

    Pulse Staircase Ramp Generator

    If you wish to use a PIC, AVR or 8051 uC, then use it to time and control a built in D-A convertor or PWM. This is done in the code or firmware.

    So .... clock >> counter >> digital to analog >> Ramp = you got it. You can implement in both software or hardware, it is your choice.


    Make an Encoder for your Bot

    I want to build a cheap wheel encoder by myself. - Need some help here. I want to build a cheap wheel encoder by myself. Now, my idea was to use a photodiode and a LED. What i don't know is how to use the output from photodiode to put on a GPIO on my MCU board. Do i need some resistors or something. Aaaa, i need a high level of 5V for my GPIO. I - AV

    Answer - Please study Links Below

    Optical Encoder Project - "Many years ago, I competed in MASLab, an MIT competition to build an autonomous robot. A year or two after that, I was on the MASLab staff, helping prepare the hardware for the year's competition. One of the projects I worked on was an optical encoder."

    About Encoders and How to Make an Encoder Wheel

    "A typical encoder uses optical sensor(s), a moving mechanical component, and a special reflector to provide a series of electrical pulses to your microcontroller. These pulses can be used as part of a PID feedback control system to determine translation distance, rotational velocity, and/or angle of a moving robot or robot part."

    Make your own rotary encoder

    Make an Encoder for your Bot

    "In the first and second post of this series you saw the basics of how to use photointerrupters. Now it’s time for practice. We make a rotary encoder. Here we take a single photointerrupter that gives us the pulses we can count."

    Make Your Own Encoders chat - "I'm starting a·dedicated·thread on the specific encoders I used on my Homebuilt platform. I had great results. A word about the encoder disks: they must be mounted PERFECTLY to achieve consistency. Perfectly flat, true, and concentric.

    Incremental Optical Encoders

    Here is a method for making an encoder with two sensors for your application. If you only need speed sensing, you may want to skip down to the construction section. The important variables are the radius of the circle (r), the distance between the two optical sensors (s), and the number of divisions in the wheel (d). .....

    Use a photointerrupters, even from an old wheel mouse if you want or build one. Then you need a Wheel with stripes and a Schmitt Trigger Gate or Comparator

    A rotary encoder, also called a shaft encoder, is an electro-mechanical device that converts the angular position or motion of a shaft or axle to an analog or digital code.

    Monday, May 02, 2016

    Piezo Power Shoes with LEDs

    Walking is a Source of Energy that can be Harvested to Power LEDs or Wearables. It may one day Recharge your Smartphone or tablet. Just start running when the Battery goes low on your Phone. -

    A question in the G+ Community lead to a study of resources in the web for this college project.

    Here is the first page that will interest you - Parasitic Power Shoes Project

    Energy Harvesting in Shoes for Small Devices

    "environmental energy sources can begin to replace batteries in certain wearable subsystems. In this spirit, this effort has examined devices that can be built into a shoe, (where excess energy is readily harvested) and used for generating electrical power "parasitically" while walking."

    Goal: To develop a rugged piezoelectric shoe insert and complementary conditioning electronics for unobtrusive, parasitic harvesting of the compression energy normally lost while walking

    See also Energy Scavenging with Shoe-mounted Piezoelectrics

    "Abstract of pdf below — Much energy harvesting research has been conducted with ceramic based piezoelectric transducers on account of their relatively large electrical response to mechanical excitation. However, notwithstanding their comparatively low piezoelectric coefficients, piezoelectric polymers too hold promise as energy harvesting materials due to their flexibility and strength which make them ideal candidates for use in more diverse applications. "

    Piezoelectric Energy Scavenging In Shoes

    "The energy harvester devices are capable of capturing environmental energy and supplanting the battery in a stand-alone module, or working along with the battery to extend substantially its life. Vibration is considered one of the most high power and efficient among other ambient energy sources, such as a solar energy and temperature difference."

    Development Of Energy Harvesting Source From Piezoelectric Shoe

    Piezoelectric materials (PZT) can be used as mechanisms to transfer ambient vibrations into electrical energy that can be stored and used to power other devices. With the recent surge of micro scale devices, PZT power generation can provide a conventional alternative to traditional power sources used to operate certain types of sensors/actuators, telemetry, and MEMS devices.

    Power Walking - STAB Resources

    "i started by looking at the self-powered shoe from Responsive Environments group and wanted to acquire a large piece of piezo film that could be embedded in the sole of a shoe. After consulting with Mark Feldmeier, I learned that the piezo elements large enough to generate enough power for the shoe would be too expensive to use if I wanted to make more than just a single prototype."

    Piezo-Powered Self-Lighting Circuit

    Thursday, April 14, 2016

    ICL7129 AD Converter needs Triplexed LCD

    I'm using the ICL7129ACPL to construct a simple 4-1/2 digit DVM. I looked over the application notes on FE LCDs on a similar post and noticed that it listed the FE0206 4-1/2 digit LCD as compatible with the ICL7129 so I went ahead and ordered one. I did not notice that the FE0206 has a single backplane listed (BP on pins 1 and 40) whereas the ICL7129 has three seperate backplanes (BP1, BP2, and BP3).

    ICL7129 AD Converter needs Triplexed LCD

    My question is:

    can the three separate BP pins on the ICL7129 be combined somehow to accomodate the single BP pin on the FE0206 or do I need to order a different LCD? If yes, how? Thanks in advance for any help you can offer.

    Mail from CC USA

    You have to buy this..

    Digi-Key - 153-1055-ND Varitronix - VIM-503-DP-FC-S-HV. Its part no is - VIM-503-DP-FC-S-HV from Varitronix.

    Another could be Mouser Varitronix LCD Displays. Ensure you buy correct part number, It is a Triplexed (like Multiplexed) Display.


    Related Resources -

    ICL7129A, MAX7129 - Maxim

    Low-Noise, 4 1/2 Digit, Single-Chip ADC with Multiplexed LCD Drivers

    Some Features -
    • ±19,999 Count Resolution
    • 10pA Max Input Bias Current (MAX7129)
    • 3┬ÁV Peak-to-Peak Noise (ICL7129A)
    • Overrange/Underrange Outputs
    • Precise 10:1 Range Select
    See Also Millivolt Circuit ICL7129

    Tuesday, April 12, 2016

    Technology Resource - Silicon Sam

    Technology Resource - Silicon Sam

    Sci.Electronics.Repair Frequently Asked Question(s) (or S.E.R FAQ for short) Home Page. This site features Samuel M. Goldwasser's latest and greatest "Notes on the Troubleshooting and Repair of..." series of comprehensive repair guides for consumer electronics equipment and other household devices. There is also a great deal of other information of interest to the electronics hobbyist, experimenter, technician, engineer, and possibly even the dentist and poet. Included are the now quite comprehensive and massive "Sam's Laser FAQ".
      Sam's Laser FAQ has a great deal of information on a variety of laser and optics related topics including a comprehensive treatment of diode, helium-neon, argon/krypton ion, and CO2 lasers as well as amateur laser construction including numerous examples of truly home-built lasers. Much of this is not available anywhere else either on-line or in print!

      Home-Built Diode Pumped Solid State (DPSS) Laser

      Home-Built Diode Pumped Solid State (DPSS) Laser

      This generates green light at 532 nm which is not a bad shade of green and quite close to the eye's peak sensitivity. This is the approach used in modern green laser pointers and most modern DPSS green lasers. While other materials can be used to obtain other wavelengths (blue being the most common)

      Friday, April 01, 2016

      Sourcing the SP646 Solid State Relay

      I have a customer that call out a Solid State relay and i cannot find any information on it. Can you help? It is a SP-646. I need a quote on 60 and 120 pieces.

      Mail from PG US

      Have a look at this, is this what you want. SP646 1 Form A Solid State Relay. contact them if the specs are right. this is made by Solid State Optronics (SSO)

      SP646  bi-directional multipurpose relay


      The SP646 is a bi-directional, single-pole, single-throw, normally open multipurpose relay. The circuit is composed of one LED on the input side which activates an optically coupled IC on the output - controlling the firing angle of two back-to-back SCRs. This circuit assures no false triggering under most adverse conditions, and a tight zero-volt window not exceeding 5V.

      • Inverse parallel SCR output
      • High transient immunity
      • 400V blocking voltage
      • 1.2A maximum continuous current
      • Low input control current
      • High input-to-output isolation
      • Solid state reliability
      • Zero-volt switching

      Programmable controls, Valve control, Solenoids, Remote switching, Home appliances, Metering equipment, Heating elements, Gas pump control circuitry,

      The SP646 Data Sheet includes the Complete Overview, Electrical Characteristics, and Schematic Diagrams.

      Even if you dont find the same number, Digikey or Mouser may have an Equivalent. Just match the Electrical Specs and PCB Footprint, pitch etc.

      Components Suppliers - Kits and Parts

      Have a Look at my Solid State Relay Pages too

      Solid State Relays -  They are called SSR as there are made of semiconductors and have no moving parts to wear out. They do generate heat depending on load and switching. Thyristors are used in most as they are rugged, mosfets and IGBT may also be used for various applications.

      DC-DC SSR


      Sunday, March 20, 2016

      Precision Temperature Control with PID and SSR

      I want to make a furnace controller by PID and SSR that can control temperature of the precision of .1 degree.Would you suggest me some controller and SSr that can do this job

      from RV

      You have to use a RTD or IC Sensor for more measurement accuracy. The control accuracy can be obtained by a Auto Tune PID controller and Thermally Optimizing the System or Equipment. That means Heat Transfer, Sensor Position, Sensor Size, Heater Type, Fans, Thermal Inertia and many things that can be studied by experimenting or learn it from the field engineers.

      from delabs

      Notes -

      If the system is a small chemical bath you need to stir with motors for convection, if it is an Oven a Fan for air circulation may be required. The control signal from the controller can be a PWM pulse train or 4-20mA depending on what you drive. A pulse train for a DC SSR or 4-20mA for a DC Drive. The Controlled Actuator may be a Heater, Fan or Compressor.

      If it is a temperature of 20 deg C, that needs to be controlled and the product is for the global market. Then you need a heater to bring a temperature to 20 deg in Alaska, but in Congo a 20 deg can only be obtained by Cooling the system.

      Precision Temperature Control with PID and SSR

      A Block Diagram showing how a Temperature Controller and SSR is used in Control. For Furnace more SSRs and more Heaters have to be used.

      Create SSR banks in the control panel and many Heaters well distributed in the heating area. Use a PID or Proportional controller with On/Off output for SSR control.

      For very Large Systems use a Booster Heater bank and Separate Controller only for the Start Up.

      See my Temperature Measurement and Control you will understand better.

      Thursday, March 17, 2016

      Hypersonic Speakers - Acoustic Heterodyning

      i have been searching for any technical help regarding my project, hypersonic speakers,but my efforts were in vain. hypersonic speakers are interesting to work upon. kindly guide if if you have any knowledge regarding the topic. Mail from GA

      This looks like something from the "Believe it or not", I cannot understand it well, but logging it here. - delabs

      What Are Some Woody Norris Successes?

      Hypersonic Speakers - Acoustic Heterodyning

      Hypersonic Sound: Sound From Thin Air - Mix two signals in a nonlinear medium and you'll end up with four - two at the original frequencies....

      "Acoustic heterodyning can be created by a single transducer or by a pair of transducers. A single transducer would be fed a signal at a "carrier frequency" and a second signal that would provide the desired (audible) difference frequencies when mixed with the carrier. If a pair of transducers were used, one would operate at the carrier frequency and the second at a frequency required to produce the desired output.

      If the carrier frequency of the transducer were 200 kHz, an upward swing of 20 kHz - or just 10 percent - would cover the entire audio range. In theory, this should result in a response that is virtually flat across the audio range - something that no speaker"

      Hypersonic Sound speakers are like Invisible headphones.

      Sound technology turns the way you hear on its ear - Woody Norris, inventor of ultrasound technology,

      Acoustical Society of America Lay Paper on Hypersonic Sound: -

      HyperSonic Sound HSS from American Technology Corporation employs ultrasonics to create audible sound in the air. It works by using harmless ultrasonic tones that we can't hear

      More from Woody Norris - HyperSonic Sound. speaker

      "With conventional speakers, the sound is projected by moving the air containing the sound waves against a cone moving back and forth inside the box. But with Woody's speakers, it's a process that happens in the air itself. Sound is beamed at the wall and it comes off the wall where it is imbedded on top of the ultrasound. A process that happens in the air unimbeds it, or demodulates the two, so in essence, the room in which you are using the speakers is, itself, the speaker box. "

       Meet Woody Norris


      Thanks for your reply for hypersonic speakers , but sir i am unable to have any positive feed backs as far as its making is concerned, i have contacted hypersonic industries also in this context, but they want me to buy a unit. i will see what i can do. thank you once again for your help.

      Reply from GA

      I dont know if this idea is good for college projects, but you can buy a Hypersonic Speaker and demonstrate an application in automation.


      Friday, March 11, 2016

      Low Cost Simple CFL lamp

      my earlier email ,went unanswered.....  i need some circuit whiz to design a -----Low Cost / Simple discrete component (may include 555 IC ,but no Custom Ballast ICs..)  CIRCUIT----to light up a 7 watt 4 pin, CFL from a 6 volt 4 AH battery +220 volt mains+3 watt Solar Panel

      the idea is to make available, reliable lanterns as product, or as a SKD / CKD KIT form, to enable local assembly for poor

      mail from SRM

      IRPLCFL2 design has schematic and BOM. 

      IRPLCFL2 design has schematic and BOM.

      The CFL-2 is an electronic ballast design for driving a 42 watt compact fluorescent lamp from a
      120 or 230 volt AC line. The circuit was designed using the IR2156 Ballast Driver IC. The main
      features of the circuit are programmable frequency, preheat time, over-current threshold and
      dead time.

      More Reading


      Sunday, February 07, 2016

      Millivolt Circuit ICL7129 MAX7129

      My application is to calibrate some instruments with help of this source. I've studied your circuit earlier also., but I want a battery operated mV source. upto 100mV full scale which is portable but still very accurate. The better the accuracy more good for me! I want to use 9v battery or a set of rechargeable batteries for powering this circuit.

      I've constructed some prototype tell me how can I send you the schematic? (file format e.g. jpg, *.tiff, *.bmp etc..., i'm using Orcad 9.2 and Express PCB Schematic softwares for Schematics).

      Also I need a 4 1/2 digit LCD display for this circuit(Or any good one). I'm referring ICL7129/ Max7129 IC datasheet for this. Do you have any 2v DVM/ DPM circuits, can you please email me the same! ...please!

      Mail from MO

      Beckman Multimeter with the  ICL7129

      "Unlike the HD110 however, this is a 20,000-count 4½ digit model with RMS-responding AC capability."

      Beckman Multimeter with the  ICL7129

      ICL7129A - Low-Noise, 4 1/2 Digit, Single-Chip ADC with Multiplexed LCD Drivers

      The Maxim ICL7129A/MAX7129 is a high precision monolithic 4-1/2 digit A/D converter that directly drives a multiplexed liquid crystal display. Using a novel "successive integration" technique, the

      About millivolt source look here Circuits FAQ - Millvolt Source see another see millivolt source, pdf at Analog-2 - Instrumentation Circuits


      I have completed the millivolt circuit, but I need some more information regarding using ICL7129 for driving a 4 1/2 digit LCD for displaying the

      Mail from MO

      Friday, February 05, 2016

      Metal Detector Circuits Problem

      With the best wishes for you. I found your address and browsed your website. I have a question and hope to take your help and answer.

      I need to good metal detector's circuit and I find several in the web, any of them worked ? what is a problem in them and where can I find one that works with best depth? Could you design or point the mistake in some circuits? Thank you for your answer beforehand.

      delabs - See my Related Page at  Metal Detector Projects

      Metal Detector Circuits Problem

      Mail from AS


      Thank you for your answer and sites. But some of them that are professional namely "twin loop" built but it has problem and didn't work.

      I think it may be a indicated, there is a problem with them. How can I make it correctly? could you proper design such circuits?

      I am not professional and of you do, I will pay for your works.

      Reply from AS

      If you clearly specify what you want with a drawing, And indicate what you may be able to pay and your contact details too.......

      Then, I will publish your request in my site. People visiting my pages may contact you. You can Try it out, I may not be able to help now.


      (PS - You can offer a solution to AS's Problem, post your design page details, All Comments are moderated, Commercial or Business comments will be deleted, designers can indicate homepage.)

      Thursday, February 04, 2016

      LF353 - Wide Bandwidth Dual JFET

      These devices are low cost, high speed, dual JFET input operational amplifiers with an internally trimmed input offset voltage (BI-FET II™ technology). They require low supply current yet maintain a large gain bandwidth product and fast slew rate. In addition, well matched high voltage JFET input devices provide very low input bias and offset currents.

      LF353 - Wide Bandwidth Dual JFET 

      (Google Talk Transcript - Year 2006 )

      Audio Tone Control with LF353 - Bass and Treble and Mid-Range(Presence). Bass is like Drums and Woofer. Treble is like Guitar and Tweeter. Mid-Range is like Vocal and Medium Speakers.

      This circuit is to demonstrate the capability of the Opamp. The post is more related to instrumentation.

      Audio Tone Control with LF353

      TF (12:16:46 PM): i need a clarification on OpAmp
      delabs (12:16:57 PM): ok tell me
      TF (12:20:55 PM): what parameter should I check to know the frequency response of an Opamp
      TF (12:20:55 PM): the thing is i am reading about a perfect rectifier
      TF (12:20:55 PM): so i am trying to find out how to get its maximum frequency
      delabs (12:21:14 PM): ok
      delabs (12:22:02 PM): you mean precision rectifier
      TF (12:48:56 PM): are u there sir
      delabs (12:49:17 PM):
      delabs (12:49:03 PM): These devices are low cost, high speed, dual JFET input operational amplifiers with an internally trimmed input offset voltage. They require low supply current yet maintain a large gain bandwidth product and fast slew rate. In addition, well matched high voltage JFET input devices provide very low input bias and offset currents. The LF353 is pin compatible with the standard LM1558 allowing designers to immediately upgrade the overall performance of existing LM1558 and LM358 designs. These amplifiers may be used in applications such as high speed integrators, fast D/A converters, sample and hold circuits and many other circuits requiring low input offset voltage, low input bias current, high input impedance, high slew rate and wide bandwidth.
      delabs (12:50:16 PM): Characteristics of Operational Amplifiers
      TF (12:52:03 PM): checking
      TF (12:52:26 PM): i think slew rate would be the parameter
      delabs (12:52:42 PM): great, you got it

      Sunday, January 24, 2016

      Drive or Fire Thyristors SCR with Pulses

      message: Hi, i'm looking at building a power supply 0-35v ,0-100A adjustable cv and cc. I stumbled across your circuit drive-scr-thyristor-with-555 is there a link to describe what phase logic is required to complete the basic design ?

      What would the cost be to supply me a working design based on thyristor control ? my use is for electroplating, i'm not trade, but an enthusiastic amateur Kind regards

      SA - USA - 2010

      I will not be able to supply prototypes or make one for you. I could help with the system design. Electroplating Systems can be made with Thyristors or MOSFETS.

      Thyristors, SCR, Triacs are driven by Pulses. The pulses must have adequate current and voltage levels. This depends on the Power of the device and see in the specs.

      Unlike Power Transistors that need continuous bias to keep it ON, these devices just need to be Fired and may need a Isolation Pulse Transformer too. MOSFETS may need a continuous bias and very less drive current, but the ON pulse must overcome the gate capacitance.


      Tuesday, January 19, 2016

      Speech Recorder and Sound Syntheizer

      I needed some help with available ics to build a small sound recorder able to hold about 120 seconds of audio, preferebly voice. I managed to find one that uses an ISD25xx series ic, which is not available within this region.

      mail from RT

      Look at these pages......

      Speech recognition using HM2007

      "Isolated speech recognition systems can just handle words that are spoken separately. This is the most common speech recognition systems available today."

      Speech Recorder and Sound Syntheizer

      Paradoxical Sound Syntheizer

      "The main property of paradoxical sounds is that their frequency do not change when you go an octave higher. This property is achieved thanks to an appropriate spectrum modelling."

      A Digital Speech Synthesizer, the S3610 LPC-10

      "Such sound-storing and playback chips are known as digital synthesizers, and they have been around since 1978, when Texas Instruments introduced the first single-chip speech synthesizer. TI's creation was first used in a company product called "Speak and Spell" - a toy that caused quite a stir and became very popular."