delabs Circuits

Tuesday, December 16, 2014

Sound activated RF remote relay

I am to build a circuit that operates off some kind of sound input into a sound activated circuit, preferably some kind of voice operated relay circuit. This relay is then to operate some kind of signal transmitter such as RF which activates a signal receiver and outputs onto a buzzer and an LED. It is to work something like a baby monitor, but in quite a simplified fashion, nothing too complex. I would be interested in circuit diagrams and related documents.

mail from CK

What is the max. distance between transmitter and receiver. Is it to monitor if the baby has woken up?

Voice Activated FM Transmitter - Alltronics

Voice Activated FM Transmitter - Alltronics

A sound activated switch and an FM transmitter joined together to make a voice activated FM transmitter. Set the level of sound that it will respond to. Two stage transmitter needs tuning to get best results. Tuning Kit and instructions enclosed. Transmits up to 1 km in the open depending on the aerial used. ZTX320 transistor specification.


The max distance between transmitter and receiver i would say would be no more than 20 meters or so. It should be designed to activate the transmitter when the vox detects noise up to 5m away, which would the trigger the remote alert device.

Look at a Solution here from TI (2014)

Baby Monitor TI App

Baby Monitor TI App

Baby Monitor is a capture and display system used to remotely watch infants. At the capture side, a microphone and a camera are placed near the child to transmit audio and video to the care giver. A parent talk-back audio system is also provided where baby can listen to the voice of caregiver.

A baby monitor is a video-based product used to see and hear an infant when the caregiver is physically not present near him/her.

I have already looked at a number of schematics and circuits i have found through my research on the internet and at my local library. I have already seen the circuit for the link that you provided, (Voice Activated FM Transmitter) and that would be ideal for the first part. I just need to know now what i would need for the receiver and remote alert unit: schematics, etc, and whether the receiver unit component values are dependant upon those of the transmitter. (All the receivers schematics I have found up to now are designed to receive speech and music like a radio.... I want to use the receiver to activate a buzzer and LED, as a remote alert device, I suppose this could also be used as a noise activated intruder alert system too!)

mail from CK

I am still trying to understand your requirement. 20 mts is quite small and is easy. What is the frequency range you need for min interference with your other gadgets. Also what are the parts your are looking at, do you need very low cost solution ? Is it just for your home use or is it for production ? will a toy circuit do ?

If you want a modern circuit, the best way is to use ready made modules. these may work at 30-200 Mhz range, some are AM some are FM.

The microphone goes to an amp which turns on one bit of the transmitter. The receiver decoded output can drive a buzzer, relay or LED as chosen.


20 meters is an adequate distance as generally the circuit is intended to be used around the house while the child is upstairs sleeping, so 20 meters should cover that quite well.

I have no other gadgets operating on radio frequencies within my home, so that should not really be a problem, i don't think.

I would prefer, if possible, an economic solution to this, a really simple circuit would do fine, however I don't want to purchase a 'hobby' kit to do this, I would prefer the circuit diagrams so I can see what parts for it i would need to get for myself...that is not a problem.

mail from CK

You must be able to study, build and test them and troubleshoot if required. i can just guide you to put things together, RF is delicate and difficult work. remember after all the efforts you put, it may not work, if you are not persistent.


Sunday, December 14, 2014

Analog Ground and Digital Ground

I need a few tips from you on Analog design in general: I have seen that a lot of ADCs have a separate AGND and DGND, but they are shorted at the chip. I believe this is required to keep the noisy digital return paths sperate from the analog return paths.

However if both get shorted at the ADC what purpose will it serve? Do you know any good application notes which clarify this ?

mail from TF

Some ADCs have differential inputs which are some times not used. Strain gauge bridge amplifiers may need differential measurement. When common mode measurements are made one end can be grounded.

Compatible Electronics, Inc - Specialize in EMC testing for FCC as well as EMC / EMI testing for CE Mark compliance under the Electromagnetic Compatibility Directive.

Grounding Demystified - Seminar of Compatible Electronics Inc

Grounding Demystified - Seminar of Compatible Electronics, Inc

In Other ADCs the analog ground and digital ground may be shown shorted in circuit.

The digital ground carries the power current to digital circuits in the chip. This current will have pulses due to switching of many digital outputs. The short, wire or link shown is circuit is assumed to be ideal in design. In fact the short, wire or PCB track has resistance, capacitance and inductance. These small values of RLC in a PCB track can cause strange AF-RF behavior.

Staying Well Grounded Analog Devices

Successful PCB Grounding with Mixed-Signal Chips Maxim Integrated

The ideal is the digital ground should be a track going directly to supply ground. The analog ground should be a track linking to the measurement circuits or sensors. The analog and digital ground now should be linked close to chip. This link will carry no current, so no ground loop, so no lifting of ground.

This ground problem can reset microcontrollers or timers when a solenoid or relay operates. Similar problem produces hum, feedback oscillations in Audio systems.

Radiating grounds, ground planes, thick tracks, decoupling caps can be remedies. see this link too.

Noise and Hum in Audio Circuits


Saturday, December 13, 2014

Millivolt Source for Calibration

I was looking for a simple MILLIVOLT SOURCE for ion electrode testing and came across your pdf schematic. This design would appear to fit my needs perfectly, but I have a couple minor questions that I hope you could provide answers for:

The pdf drawing (Document Number ST02) is not clear with respect to the U4 op amp circuit, namely the connection of components R9, P4, and R10 to the op amp. I assume they connect to U4 pin 1 and pin 8 respectively as a balance or offset feature -- maybe you can confirm this.

Also, it is not shown where the terminals of the potentiometer P4 connect to -- do they go to Vcc and Vdd? And where does the slider 2 connect?

There is no problem with the rest of the circuit being readable. I expect capacitor C7 would have to be a low leakage type.

NPN transistor Q1 is shown as a BELL100, which I could not find in my catalogues. Could you suggest a suitable replacement?

Thank you for taking the time to check these points. Your answers will help in bread boarding this instrument

mail from AS

R9, P4 and R10 are for balance and offset as you said you can use it that way, but see the new circuit.

Millivolt Source for Calibration

Millivolt Source In this link see at bottom this circuit millivolt source, pdf.

I have put a better offset null, OP07 has around 75uV offset error which may show as +/- 1 count error on 4 1/2 DPM 19999 counts. You can skip it if you are using a 3 1/2 digit DPM as the error will not show, even it 4 1/2 it may be upto 2 counts only.

C7 can be a low leakage plastic cap, even a tantalum electrolytic is ok, aluminum electrolytic may cause a very small error.

Q1 can be any npn that can take 100mA current, do not use RF devices, 2N2222 is best.

If you use a DPM protect DPM inputs with clamping diodes or zeners or an error in bread-boarding may send +/- 12V to DPM and it may be damaged. Some DPMs come with protection like DMMs. use the circuit in del2003.pdf in analog section to make a 4 1/2 DPM.

Also in 2000mV range do not short outputs as the Q1 may get damaged, and in 200mV and 20mV range the output impedance is 10 ohms which is good for calibrating any high input impedance instrumentation like a process indicator etc. loading with 100K 10K will cause error.
Most instruments are very high impedance so it is fine.


Friday, November 21, 2014

digital weight Indicator

I need some details of a digital weight Indicator.

mail from CA

study these useful links.......

Introduction to Load Cells at Omega

A load cell is a transducer which converts force into a measurable electrical output

LC101 and LC111 Series:S-Beam Load Cells

LC101 S-Beam Load Cell

S-Beam Load Cells S-Beam load cells get their name from their S shape. S-Beam load cells can provide an output if under tension or compression.

Measuring Strain with Strain Gauges at NI

"The metallic strain gage consists of a very fine wire or, more commonly, metallic foil arranged in a grid pattern."

 Bonded Metallic Strain Gage


Wednesday, November 19, 2014

Electronic Fifteen LED Roulette

The following was submitted on July 11th, 2007 at 12:47AM (PDT). Message: I want to combine Ne555 with 74154 IC.The indication of the outputs must be shown with LED's but up to so far it need 15 outputs ,is it possible the way i did? if not i will need your assistance

Mail from CY

LED running lights are used to decorate Christmas Trees, Festival Surroundings and even  Buildings. A Clock and a counter are basically required. Many LEDs can be used in parallel with driver transistors. Upto 15 count is is good enough. Many colors can be used and with a PWM or VCO you can make it Audio or Music effects lights like strobe lights.

Electronique RĂ©alisations - Roulette

Multi-Colored LEDs and drivers and even PIC microelectronics with Visual Effects in the form of ROM tables can make Alphabets and Numbers appear in LED arrays. Some have made Mini Ocillosocpes and Toy Spectrum Analyzers too in LED DOT Matrix Arrays.

LED Sequencer Circuit

Electronic LED Roulette

See these circuits you will get an idea, Using CD4514 is also possible.

555 and CD4017 Running Lights


Monday, November 10, 2014

Isolated Full-duplex Serial Interface

I would like to build Optoisolated RS232 interface. I've googled a little bit, and I came across your design:

RS232 with Opto-Isolation

However presented schematic is of poor quality - I'm not able to read all parts numbers and their values. Is it possible for you to send me a copy of this schematic, which is more readible?

Mail from M from Poland

You had written to me a few months back, I suggest this circuit

Isolated Full-duplex Rs232 Interface

This self powered interface circuit electrically isolates the TxD and RxD lines from the PC serial port and protect the PC from direct connection to hazardous voltages.

See also Isloated Interface to Microcontroller

See a Commercial Solution you can buy

CVT-232A-3 port-powered 3-wire RS232 Isolator

CVT-232A-3 port-powered 3-wire RS232 Isolator

"The unit features 5000V opto-isolation circuitry and optically isolates three (3) RS-232 lines (TX, RX and GND), which effectively protects your RS-232 devices from ground loops, noise problems, transient surges, remote lightning and spikes."

Saturday, October 25, 2014

Hobby Diy Oscilloscope

Is it good as a (beginner) hobbyist to crave for an oscilloscope.  mail from EA

This scope will work from your PC Audio Card or Sound Card. You First need to build the circuit below and connect it to Line-in of Sound Card.

xoscope for Linux

xoscope is a digital oscilloscope using input from a sound card or EsounD and/or a ProbeScope/osziFOX and will soon support Bitscope hardware. Includes 8 signal displays, variable time scale, math, memory, measurements, and file save/load.

Hobby Diy Oscilloscope

Zelscope: Sound card oscilloscope and spectrum analyzer

Zelscope is a Windows software that converts your PC into a dual-trace storage oscilloscope and spectrum analyzer. It uses your computer's sound card as analog-to-digital converter, presenting a real-time waveform or spectrum of the signal.
Digital PC Oscilloscope
"Our group decided to pick the Personal Computer Oscilloscope because it sounded very interesting to approach. We also felt it would help us in understanding many aspects of hardware and software interfacing. We also wanted to do something that we felt was consumer electronic related to the current market and was interesting in working with."


Friday, October 24, 2014

Secure Entry Access Control - Smart Cards

I am working on an access system, multi-user code for entry to restricted areas. I designed one that uses purely hardware but its a bit complicated and bulky, though it works perfectly. Might you have any ideas on implementing microcontroller based systems. Any information would help me at this stage as i am still investigating my options.

Post by RT

These days smart card technologies are used for access system in most places. It uses a RF card the size of a Credit card with a microcontroller embedded in it. and you need a smart card reader that needs to be networked or interfaced with PC. philips, atmel, maxim, fujitsu and many more sources for kits, products and parts. many embedded 80C51 family type solutions were there when it all started.

Secure Entry Access Control - Smart Cards

Smart card, chip card, or integrated circuit card (ICC)

Contactless smart cards

A second card type is the contactless smart card, in which the card communicates with and is powered by the reader through RF induction technology (at data rates of 106–848 kbit/s). These cards require only proximity to an antenna to communicate. They are often used for quick or hands-free transactions such as paying for public transportation without removing the card from a wallet.

Like smart cards with contacts, contactless cards do not have an internal power source. Instead, they use an inductor to capture some of the incident radio-frequency interrogation signal, rectify it, and use it to power the card's electronics.

Study Resources Below

Smart Card Technology and Security 

A Smart Card and a Card Accepting Device (CAD) communicate via means of small data packets called APDUs (Application Protocol Data Units).

Useful Things for Smart Card Users 

Modules for Smart Card Microcontroller, Examples for application level Communication, Connection of a Smart Card to a Microcontroller, Instructions for Smart Card current measurement.
Other Notes

When this post was first made 8 links to sites with info was added by me. Today 2012 most of the links are broken. So new sites are listed.


Tuesday, October 21, 2014

Graphic Equalizer Circuits

plz send me sound equalizer circuits. - email by AH
Search for ...... graphic equalizer circuits. You have many pages to see, and the navigation for all the pages is at bottom of every page. anyway, i did it for you,

Graphic Equalizer Circuits

10 Band Graphic Equalizer (sam)

"The circuit of graphic equalizer, allocates ten adjusting potesometer , that each one from them affects in a predetermined area of frequencies, the central frequency of which abstains a octave (double), from the central frequencies of her neighbouring regions."

3 Band graphic equalizer (andy)

This circuit is similar to ones that used to come in Philips audio books, so try this first. Now to design your own, learn the technique here ...

"Using a single op-amp this easy to make equalizer offers three ranges, low frequency,mid frequency,and high."

7 band Audio Graphic Equaliser

"The details shown are for a 7 band but the principle can be extended to almost any number of bands - if you can find accurate enough components."

Level, Tone and Balance Controls

Amplifiers, tone controls and other audio effect circuits at david's "Discover Circuits".


Thursday, September 18, 2014

Up-Down counter-timer

(A question answer thread of, nearly a decade old)

Presettable Up-Down counter-timer-Question   

I am looking for a schematic for a pre settable Up/Down counter that I can build for my church. It needs to be 5 decades. From 0:00:00 to 9:59:59. I ran across your web pages while searching for such a schematic. Can you help me out?


Presettable Up-Down counter-timer-Answer

It appears from the "9:59:59 " you have mentioned, what you need is a timer.It it a count up and count down timer you need, like a clock ?

Can you explain to me how you plan to use this circuit in the church.Visit the links below and see if that is what you want.


Presettable Up-Down counter-timer-Reply 

Thanks for the links. What I need this count down timer for is to allow speakers at the church to know how much time is remaining of their presentation. All of our speakers are taped for later use or review. The speakers giving the presentation usually go over their time limits for the audio tapes. With this unit I am trying to build time can be entered by preset thumbwheel switches. The counter is then started and times out when the counter reaches 0:00:00.

What makes this count down timer different is there will be two seperate displays. A one inch set of seven segment LED's will be in the main console with the rest of the logic. There will also be a 2.5 inch set of seven segment displays remotely connected (anout 3 feet away). The large displays will be what the speakers will see. The small displays will be in the control booth.

I already have the following items gathered up. I am hoping to use these components if I am able. I have the MC14029, the MC14513, the Allegro UDN2597A (to drive the large LED's), the Dallas Semi DS32KHz time base, the MC14020, the MC14013, the large and small LED displays, and the thumbwheel switches (set to 9:59:59 maximum)

I also have some MC14011, MC14490 (Hex Debounce Switch Controller, MC14049, and the R's and C's necessary to complete the circuit.

Does this explain what I am trying to do? I think the MC14029 counters can be used to do all the counting and store the preset values. All I have to do is add the reset at 6 for the tens of seconds and the tens of minutes. However, I don't know how to connect the logic?

The DS32KHz, MC14020 and MC14013 will generate the 1 Hertz (1PPS) signal. That is about all I currently have. That is why I need some help


Presettable Up-Down counter-timer-Answer

below are two circuits in pdf format see if they are ok see... Digital Circuits-2

Circuit 1 - Digital Timer Clock With Preset using Thumbwheel switch.

Circuit 2 - 1 Hz or 1 pps crystal clock using CD4060 and 32768 Hz Crystal.

They have not been tested much... The 4513 control pins 8-4-5-3 connections verify, as i did not get the datasheet.

the circuits will work as concepts are right, but some tweaks in R C values may be required.
the R C values can only be corrected if you have problem in making it work.

the main problem in the R C values may be related to "the reset at 6 for the tens of seconds and the tens of minutes". tell me what changes you may want. this is a presettable count down timer upto 99.59.59 hours.minutes.seconds


Wednesday, September 17, 2014

Temperature Meters with Analog Recorder Output

I would like to know if you offer a monitoring solution that will constantly measure ambient (air) temperature (say, 0 to 150°F), and provide a corresponding DC voltage output of either 100 mV, 1 V, 5 V, or 10 V. Do you make a unit that can be configured to do this?

Mail From JPE - WV - US

Analog outputs were very popular as they are inputs to Strip Chart Recorders, Later they had an extra use for PC Based Data Acquisition, data Loggers and PLC. Now we have Instruments with digital and wireless outputs too.

Temperature Meters - DP116 - Omega
Economical 3/64 DIN panel meter that has a full size 0.56" green or red LED display, with a built-in analog output and display hold capability. 3 1 /2 Digit Display.

Features Include
  • Thermocouple and RTD Input
  • Full-Size 0.56" (14.2 mm) LED Display
  • Analog Output Standard
  • 1 /8 DIN Panel Adaptor Standard

Economical Digital Meters DP18 - Omega

Economical Digital Meters DP18 - Omega

The DP18 series is a complete family of panel meters with input cards for voltage, process and temperature measurement and control. The signal conditioners for voltage will measure ac or dc voltages or true RMS.

Modular Design, Options for Alarms, Analog Output of Communications, 3 1/2-Digit LED Available in Red or Green Displays


Friday, September 12, 2014

Noise and Hum in Audio Circuits

"I currently have a car stereo set that i use as an amplifier in my living room. but my main problem is that i a lot of noise hum when ever it is on especially when there happens to be a drop in the supply Voltage. i decided to use a voltage regulator and capacitor across (1600uF)...but it only reduced the hum a little. how can i completely eliminate the noise". - Question  by FP

Answer by delabs 

Ensure that the power supply has a full wave or bridge rectifier. If power supply transformer is say 12-0-12 two diodes must be there and a center tap ground OR If a square or round bridge is used with four leads or four diodes, then it is fine. Half wave rectification or a blown or leaky diode can cause this problem. Put all the filter caps you want and add a series choke as well the better the power supply the audio will be good.

Noise and Hum in Audio Circuits

The power supply transformer rating - voltage and current both may need to be boosted. Some very low budget transformers do not use CR-GO plates for lamination (i think it is Cold Rolled Grain Oriented ). They use plain thick metal plates without coating and hence hysteresis and eddy current both cause problems. Then you have ground loop hum and noise of semiconductors, the speaker ground and amplifier ground carry current and they should be directly connected to power supply ground, These you can understand by looking at these pages......

I am only aware of Phillips transistor based designs used 20 years back, but these have more...

Noise in Audio Amplifiers

"Noise has enormous nuisance value with sensitive (i.e. high gain) circuits, but the information provided by most IC and transistor makers.."

Avoiding Ground Loop Hum

"To solve the problem, the goal is to reduce the magnitude of the loop current. This is done simply by inserting isolation resistor(s) in series with the audio cable ground(s)..."

Audio, Power, and Control Lines

"The correct place for an audio ground is at the microphone connector entrance to the shield enclosure of the radio..."

Saturday, August 23, 2014

Microcontroller and SBC in Real World

details required for... Atmels 89C52 Microcontroller A/D D/A converter Keypad LCD display(Or LED Display) 5V Regulated power supply. Temperature & Humidity controller using PID control algorithm implemented using Atmel's 89C52 microcontroller for a AHU unit ( Analog Input from the sensor(4 wire) 0-10v dc & Output from Microcontroller is 4-20mA to the Actuator through a DAC converter).

The Temperature & Humidity to be controlled are 24±1 degree Celsius and 55%±2% Rh respectively. provide me with good LINKS.

mail from SA

Get a sensor that gives a 0-10V or 4-20mA proportional to RH% and Temp deg C. what you need to do now is to select a A/D and a D/A for a real world interface

you can visit these links.......

DigiThermo Wichit Sirichote

DigiThermo 0-100.0 °C Wichit Sirichote

Build your own a laboratory instrument for measuring time and temperature. The DigiThermo demonstrates the use of 'C' language, a dual-slope converter, LCD interfacing, and digital filtering as well..

The Assembly language program for this may be the complex, due to PID. and my uC pages micro-delabs also in my other pages you can find theory on PID etc, in them i have MCS51 code for 2 setpoint process controller.


Other uC projects sites links

Temperature and Humidity Meter -  This project is a combined temperature and humidity meter. It is an improvement on my PIC-based humidity meter and my PIC and AVR thermometers. I use an ATmega164, which as lots of I/O and memory.
    Temperature and humidity measurements with the AVR web-server- The tuxgraphics Ethernet board has a lot of general purpose IO pins where external hardware such as sensors can easily be attached. In this example we use the sensirion sht11 sensor to measure temperature, humidity and calculate the dew point.

    Friday, August 22, 2014

    Working with SMD and SMT PCB

    One thing tho, i would like to request you to send me some procedures on how to work with surface mount devices (SMD's). I cant get the IC as DIP so i have no choice but improvise an SMD. What is your most professional advice on this? Is it possible you could help me with any procedures for using an SMD on a PCB circuit?.

    mail from CM

    Study These Links......... - SMD Surface Mount Device and SMT Surface Mount Technology

    you may need a big tabletop magnifier with light and a fine tip soldering iron to get started. It may be difficult and needs a lot of practice, but many people are able to do it.

    Surface-mount technology - Wiki

    Surface-mount technology - Wiki

    An SMT component is usually smaller than its through-hole counterpart because it has either smaller leads or no leads at all. It may have short pins or leads of various styles, flat contacts, a matrix of solder balls (BGAs), or terminations on the body of the component.

    Introduction to Surface Mount Technology and Surface Mount Devices

    By Dean F. Poeth, II, Ph.D., P.E., C.Mfg.E.
    For the Small Manufacturer and Hobbyist: Prototype Manufacturing, Rework, and Repair Techniques

    SMDs have improved performance over through-hole components due to their smaller size, shorter internal leads, and smaller board layouts. These factors reduce the circuit’s parasitic inductance and capacitance. SMDs can also be more cost effective than traditional through-hole components due to the smaller board size, fewer board layers, and fewer holes.

    Hints and Tips for using Surface Mount Technology (SMT) 

    What is Surface Mount Technology? Put Simply - It is a type of electronic component
    package. Most electronic components can be divided into two categories - through hole (TH)
    and surface mount (SM). Through-hole components have been used for many years and are
    designed to be loaded on one side of a printed circuit board (PCB) and soldered on the other.
    SM components are designed to be loaded and soldered on the same side of the PCB.

    Luke Enriquez. Rev 1.3. August 2001.
    VK3EM PO Box 98, Kerrimuir, Vic. 3129. Australia


    Tuesday, August 19, 2014

    Datasheets and IC Application Notes

    where can I find on IC data and their application?  mail from EA

    Answer by delabs

    Vintage DataBooks are a valuable source of Electronic Product Design Ideas. Study the Applications.

    Folkscanomy Electronics: Books on Electronics, Circuits and Processors 

    You will also find Radio Electronics and many other Datasheets. Even of firms that do not exist now.
    Datasheets and IC Application Notes

    One of the books here is The " Intersil Hot Ideas" - This was my Mentor Book These helped me build Intelligent Instruments in the 80s. Intersil( GE) was in advanced CMOS before anybody else. They made the smartest chips when the Microprocessors were being examined Skeptically by engineers. (At that time Microprocessors needed many support chips and consumed huge power only later CMOS uC came)

    See also delabs Resources i have created as a reference for such doubts (2007)

    Saturday, July 26, 2014

    What is a Relay - Jim Asks

    (A text chat in Google talk long ago from my email records - 2007)

    Jim: hello, anantha.
    delabs: hello

    Jim: i have a Small problem,it's about would u pls give me an information about relays,pls give different types of relays and their differences.

    delabs: for what do you want to use the relay for.

    What is a Relay - Jim Asks

    "A Relay is an electrically operated switch. Many relays use an electromagnet to mechanically operate a switch, but other operating principles are also used, such as solid-state relays" - Wikipedia

    Jim: Two door alarm settable for close or open door

    delabs: there is a control signal and an output for relay, if you are using just a buzzer for alarm, no relay needed if you want to operate a big hooter or 230V lamp a relay is needed- or even a motor or solenoid to move some thing  Even a Solid State Relay can be used.

    Bigger loads like large motors may need drives and containers. Some even have speed control. Big doors are more difficult to open and close. safety features needed.

    The picture above shows also reed relays that are used for small signals - analog and telecom. In Solid State switching also we have small signal and power switches, using mosfet or triac.

    Soldermans Basic Electronics: Relays and Contactors

    Jim: let me check dis addr nd i'll get back 2 u just now.
    Jim: ok but if i have a problem i'll get back 2 u,bye

    Thursday, July 24, 2014

    Mains Voltage Stabilizer Step up Circuit

    i kinda found myself in a place where the voltage is so low (80v-110vAC) and i need to boost it up to 220v so what can i do? i have a burnt stabilizer (that is the electronics part) so i need the electronics circuit to replace the burnt one can Anybody help?

    post by FP

    here is a circuit i made for you, i am not sure it will work, i hope it will help you learn. part of these ideas are over 20 years old. Stabilizer Circuit

    Stabilizer Step up 230V AC 500VA

    This circuit is a design i did, not tested by me as yet. It can Stabilize Mains voltage to around +/- 10% . It can be used for both 110V AC or 220V AC inputs with modifications. The Output is 220V AC. There is an overload, under voltage and over voltage trip circuit. With some tweaks and modifications it might work.

    Solid-State Stabilizer Step up 110V AC

    This circuit is a design concept, not tested by me and i did it just to explain some ideas. The circuit uses opto-coupler MOC3041 of Motorola and the Triac BTA-16-600 of ST as a solid state switch or relay. It also uses the LM324 quad opamp from National Semiconductor which is low power and single supply. As the MOC3041 switches the Triac at zero crossover there is no inter-winding short of transformer on crossover hopefully, the control circuit is designed in such a way that more than one triac will not be turned on at a time, i would like you to give feedback.

    One more circuit, this is a bit complicated and it is not tested, it may not work that easy, just refer it to make your own design, it is just a bit of theory and my experience, i may be wrong at a few places.

    Electric Circuits


    Sunday, July 13, 2014

    Lamp Dimmer DC with L296

    I need a simple circuit to drive a 12v DC (4amp) light. But, it needs to dim to 25% over a specified amount of time. Basically it needs to hold at 25% (4v) for a few seconds then fade and increase to 100%(12v) , hold for a second then fade back to 25%.

    Here are the electrical specs: - Input 12vDC @ 5amps - Output from 4vDC to 12vDC (amp draw may be as little as 1 amp or as much as 4.5) - Only 1 potentiometer is used to vary the rate at which the voltage changes from 4-12 - It must increase and decrease voltage in a very smooth way, so that it fades the light to 100% and then back down to 25%

    mail from JR

    I have a circuit in my website that may serve your purpose, visit Power Supplies Section.

    There may be some documentation errors in my circuits. If you are used to building and troubleshooting circuits then it is ok.

    Switching Battery Charger with L296

    Switching Battery Charger with L296

    L296 is a switch mode power controller here. In this NTE327 or 2N5038 is used to boost the current output. This transistor is both high current and fast switching. U1A, LM358 measures the load current by reading the voltage across shunt R6 and compared to a current limit setting at R14 using U1B to give a load current control. R7-R8 give a voltage feedback for voltage limit.


    Sunday, June 22, 2014

    RS485 Modbus - Wireless Interface

    I am working on alarm systems and would like assistance in designing wireless link for the unit, ie sensors to control panel, control panel to monitoring station.

    I noticed most of the circuits available on your sites are FM 88 - 108 MHz, which would definitely cause interference. Can you please assist me with this final part of my system.

    mail from RT

    i would like to know........... The wireless link distance of Transmitter and receiver. The frequency range you want like FM 'n' MHz Are you aware of the regulations of wireless transmission.

    What band is allowed in your country and what distance. what type of data needs to be transmitted. If this is for process control, RF should be avoided if possible. You should use 4-20mA current loops, RS485 or IR optics.


    You can study these pages ...........

    Wireless Transceiver with Modbus Interface at Omega 

    RS485 Modbus - Wireless Interface

    "The OMWT-XREC-MOD Wireless Transceiver uses an embedded 100-milliwatt frequency hopping wireless modem that provides communication between a local RS-485 network and a remote network of RS-485 connected devices. The OMWT-XREC- MOD will automatically sense the direction of data flow and switch the RS-485 and radio devices accordingly."

    Read more here Modbus Communication Protocol Suite

    with a RS485 and Modbus Network you can do it.


    Thursday, June 19, 2014

    Electronics Work Bench

    How can I get a software for an electronics work bench for my pc.

    mail from EA

    I did not understand about the 'electronics work bench' pc based instruments are made by National Instruments see links in my electronics orange pages. try to look with Picotech and Atcweb for low cost solutions.


    TINA is a powerful yet affordable circuit simulator for analog spice circuit simulation, digital and mixed circuit simulation/

    this may be what you want....i am not sure.....have a look. "Tina Pro - The Complete Electronics Lab Edison - Multimedia Lab for Exploring Electronics" ...   also CircuitMaker which you may know.

    CircuitMaker Student Edition

    Ssimulation program.... helpful for learning about circuits, testing designs or analyses, and even just drawing schematics for reports.


    Friday, June 13, 2014

    Soldering Iron Tip

    Can I use stainless steel to replace a defective soldering iron tip?

    mail from EA

    Soldering iron tips are mostly alloys of copper. the thermal conductivity of steel is poor. buy a soldering iron tip available in the local market.

    Soldering Iron Tip

    Soldering Iron Tips 60 Watt

    Weller tips are magnetic and only original weller tips to be used.

    Change Weller ET Series Soldering Tips

    Change Weller ET Series Soldering Tips

    Changing the soldering tips on a PES51 pencil is very simple. You just have to make sure to take your time and don't force anything. Damaging your iron is not only possible, but easy when replacing the tips, so proceed with care.

    The Basic Electronics Soldering & Desoldering Guide

    The Basic Soldering Guide contains everything the beginner needs to solder electronics successfully, with guidance on choosing the right soldering iron, details of various solders and fluxes,


    Wednesday, May 28, 2014

    Interface 89C52 with 7135

    i am interested in doing with 89C52. And now I trying to use AT89C52 and ICL 7135. And I use nterrupt 0 to get BCD data from ICL7135. I send you my program here and expect to get your advice soon.

    post by NHT

    I have made a circuit for you to study, also some idea about the code. you need to have Adobe Acrobat Reader

    You can find it here Microcontroller you can now try to write the code and draw the circuit you need.

    AT89C52 Parallel Interface to ICL7135

    AT89C52 Parallel Interface to ICL7135

    This circuit is an interface between 89C52 of Atmel with 7135 of Intersil.  With This circuit you can read analog data of both polarities you can change the range scale with extra circuits, you can store data on a EEPROM or send them to PC thru RS232 or Comm port.


    Tuesday, May 27, 2014

    Cypress PSoC Mixed-Signal Array CY8C27x43

    I had corresponded with you some time back when you had guided me to making a temperature controller .It was a very nice experience doing the same.

    Just for your information , I am building the same using a PSoC( Programmable System on Chip). I will give a tiny snapshot from their site FYI. PSoC Mixed-Signal Array.

    A true system-on-a-chip, PSoC devices are configurable mixed-signal arrays that integrate the microcontroller and related peripheral circuits typically found in an embedded design. Employing easy to use development tools, designers select configurable, pre-characterized library elements to provide analog functions such as amplifiers, ADCs, DACs, filters and comparators, and digital functions such as timers, counters, PWMs, SPI and UARTs. PSoC analog performance is instrumentation-quality Ă‚­ including rail-to-rail inputs, programmable gain, 14-bit ADCs and exceptionally low noise and input leakage and voltage offset.

    I use the 8C27....

    mail from TF

    Programmable System-on-Chip - PSoC - CY8C27x43

    The PSoC family consists of many Mixed-Signal Array with On-Chip Controller devices. These devices are designed to replace multiple traditional MCU-based system components with one, low cost single-chip programmable device. PSoC devices include configurable blocks of analog and digital logic, as well as programmable interconnects.

    PSoC EvalPods

    PSoC EvalPods are pods that connect to the ICE In-Circuit Emulator (CY3215-DK kit) to allow debugging capability. They can also function as a standalone device without debugging capability. The EvalPod has a 28-pin DIP footprint on the bottom for easy connection to development kits or other hardware. The top of the EvalPod has prototyping headers for easy connection to the devices pins. CY3210-27x43 provides evaluation of the CY8C27x43 PSoC device family.

    CY3210 - CY8C27x43 PSoC(R) Evaluation Pod (EvalPod)

    Friday, May 23, 2014

    Passive volume control

    please if you don't mind I need to help to find a control circuit for volume of speaker 4 ohm or 8 ohm located in the another room far away of cassette or CD player by using only passive components with potentiometer without transformer.

    mail from AD

    i have attached to this mail a simple circuit you can build at home at low cost. This is the only alternative for the need that you have specified. it uses just a rotary switch and wire wound resistors.

    Volume control circuit for speaker 4 ohm or 8 ohm located in the another room far away. by using only passive components. This gives limited control and helps reduce volume when a conversation starts. The resistors are very low value.

    Passive volume control

    Passive volume control with Potentiometer

    A simple circuit you can build at home at low cost it uses just a rotary switch and wire wound resistors. Add more resistors and a rotary switch with more contacts for finer control.


    Saturday, April 26, 2014

    Seven Segment LED display

    how is the circuit for driving a seven segment led

    mail from EA

    A 7 segment LED display is used to display a number 0-9 using 7 LEDs, The circuit you design must have a BCD output, BCD means Binary coded decimal for number 0 it is 0000 and for number 9 it is 1001 see this chart i put in my site....  Electrical Tables

    the BCD is fed to a BCD to 7 segment decoder like CD4511 or 7447 which has the logic to take care to drive your display, the displays are two types common anode and common cathode you have choose a driver to match your display, you will need to use current limiting resistors for every LED to limit current to 15mA or less. there are many circuits in my website which has examples of these.

    you can also drive such displays with 7107 or 7135 to display analog signals, or with a microcontroller like 8051 using software decoding, even such examples and code is available at my website.Digital-Circuits. and Logic-Circuits.


    I made an online tutorial for seven segment LED. Hope it helps you learn more.

    Digital up down BCD counter "Simple Digital up down counter CD4029, with interactive javascript simulation." You can run the circuit online and try out without wiring it up.

    Digital up down BCD counter

    Saturday, April 19, 2014

    Winding Transformers and Coils

    i would need your help in designing transformers for rechargeable lamps. i really don't understand what the dots in front a coil stands for. all help (including pictures) would be really appreciated. my own just packed a few days ago and i would love to recoil the transformer.

    mail from LA

    You will have to do a lot of study in the internet, and experimentation too. Transformer winding is a specialized profession not a hobby at all. You can wind some coils or small signal transformers, that is ok. Please do not try to wind mains or 230/110 V transformers at home.

    Winding Transformers

    I can only give some tips, precautions and techniques to a winder. study these links....
    I have put the link of a page but see all the pages of the website. The Dot polarity in a transformer stands for the direction of winding relative to each other. The Direction of winding could be clockwise or anti-clockwise.


    Sunday, April 13, 2014

    NE612 - Balanced mixer with Local Oscillator

    I am designing a circuit that implements an AM radio circuit that ultilises the IC Double mixer and Oscillator NE612. I was just wondering whether there is any standard symbol for this kind of IC.

    mail from CM

    There is no standard symbol for NE612, just a square box. You have to make a custom part in the CAD software or see if someone has done that. check these links on info of NE612 circuit and symbol....

    GM47: Simple 30m Band QRP CW-Transceive 

    The Rx mixer is followed by a IF stage featuring an NE592. The mixer's balanced output is directly connected to the amplifier's differential input, minimizing component count at this point.

    Simple 30m Band QRP CW-Transceiver

    Direct Conversion Receiver using NE612 for HF Bands

    The NE612 is an integrated circuit which contains a balanced mixer with its own on-board local oscillator and voltage regulator. The mixer can provide up to 18dB of gain at 45 Mhz, and the local oscillator will operate up to 200 Mhz.

    HF Transceiver using NE612

     I would be working on the Transverter first, as with this, I could try out the 9Mhz SSB Module that I already have. I would be building the Transverter for the 14 Mhz band depending on the values from my DC Receiver project using the NE612 IC

      Friday, March 21, 2014

      Guard rings in strain gauge measurement

      Hi... Can you please tell me as to what is a guard circuit used in bridges?

      Mail from SN

      The very high impedance amps for bridge circuits have inputs in tera ohms and bias in pico amps. The sensitive bridge circuits must be able to detect a 1 uV difference when a 100 gm weight is placed on the cantilever. So it is very sensitive.

      The power lines and other logic lines close to chip high impedance pins may leak pico amps to nano amps of currents, humid-air or PCB contamination or power pins being too close, the leakage currents may show as full scale reading without input.

      Read also driven gaurd - a better method

      " The basic principle is to protect the sensitive wire with a surrounding guard that is held at the same voltage as the wire, if they are at the same voltage then there will be no current flow."

      Read also driven gaurd - a better method

      The guard rings around these sensitive pins or shielding will act as return paths for the leaking nano amps.Even ionic discharge from a sharp pin with high voltage can imbalance bridge. As it is like an Electrometer.

      Read more here. guard rings in strain gauge measurement

      The Strain Gage

      Strain gage transducers usually employ four strain gage elements electrically connected to form a Wheatstone bridge circuit

      Electronic Electroscope
      This simple circuit can detect the invisible fields of voltage which surround all electrified objects. It acts as an electronic "electroscope."

      Guarded resistance bridge
      By using a guarded scanner and two sources to form a guarded resistance bridge, measurements from 100KW to 10GW can be made with excellent accuracy. This system provides a simple yet effective way to activate both the high and low guard circuits.

      Compact DWDM laser Temperature Control with the MAX8521

      The guard ring functions as follows. Because the DAC output voltage is similar to the op amp's inverting input voltage there is essentially no potential difference between the guard ring and summing junction and its associated components inside the ring. The ring intercepts outside surface leakage currents where they are shunted by the low impedance of the DAC.


      Tuesday, March 11, 2014

      Lighting a LED String - Serial Drive

      Hi there, my name is steve. I would like to ask you about the best way or the most efficient way to supply LEDs. there are 36 small LEDs or 72 small LEDs (5mm).

      could I just put then in series the 36 LEDs and a diode, resistor and plug in to AC power line (110)

      (An email i got some time back)

      Answer - Lighting a LED String - Serial Drive

      Remember that the LED for lighting or otherwise needs to be protected from over current on Forward Bias and High Voltage connection in Reverse Bias.

      That means you could use a 3 A Diode like 1N5408 to prevent wrong polarity connection. Then all you need a constant current source with a voltage output a little above the product of the Number of LEDs and Forward Drop of a LED.

      5 LEDs in Series with a forward drop of 3 each means 5 x 3 = 12. You need a 15 Volts Regulated Supply with a current limit of around 30mA or more. See the LED datasheet. Go beyond limits you lose your LEDs the same day or months later.

      Use SMPS designs for smaller sizes and it has to be Robust to Mains Power Supply Variations. Use a Surge Protection Assembly from a Reputed and Quality Supplier. (this surge part spoils the reputation of your Lighting Product and affects the entire LED lighting Business)

      Read these pages to learn more....

      The Perfect LED Light -  by Garry Petrie

      "The perfect LED light is designed for cavers who want an efficient, uniform and constant bright light for caving. This article contains some very specific technical information and it is assumed the reader has a basic understanding of electronics. To build the light, the reader also must have some experience soldering, drilling, wiring and cutting small objects."

      The Perfect LED Light -  by Garry Petrie

      A linear Constant Current LED Lamp Dimmer

      "This simple Linear circuit provides continuously variable regulated current (~25-400mA) from a 4-6 Volt source.  I chose a linear design for simplicity, reliability, ease of repair, and to avoid switching EMI in my Cave Radios.  The circuit requires only 0.2V headroom above the parallel LED Array voltage to provide regulation at maximum current. "

      A linear Constant Current LED Lamp Dimmer

      Thursday, March 06, 2014

      Electrometer, Gauss Meter and EMF Meter

      Hey folks, I'm brand new here and to tinkering with electronics in general. I'm looking into building my own electroscope.

      My question is: What's the difference between a static field and an EMF field? There seem to be detectors for both, so I wanted to know what the difference is, and what the relationship between the two is.

      Question by BCM USA

      delabs Answer

      Static Field could be Electrical or Magnetic. Electric Charge as a static Field can be measured using Electrometer

      Electrometer, Gauss Meter and EMF Meter

      Simple Electrometer - A trivial JFET electrometer isn't a new idea, there are millions of designs for them out on the Internet, this is just yet another. This one is slightly unique in that it is a bridge configuration that makes it ultra-sensitive, much more so than a gold-leaf electroscope, but less than a vacuum tube or electrometer grade FET device.

      Static Magnetic Field is measured using A magnetometer  also be called a gaussmeter. Gauss_meter

      "Magnetometers are measurement instruments used for two general purposes: to measure the magnetization of a magnetic material like a ferromagnet, or to measure the strength and, in some cases, the direction of the magnetic field at a point in space."

      EMF is the field of a Moving Magnet, an AC field. This Moving Magnet could be simulated by a Sine Wave in a Coil. Use a EMF Meter for this. EMF_meter

      See some Instruments that are used here - AlphaLab Gauss Meter and EMF Detectors