A practical electronics engineering resource focused on tested circuit projects, clear theory explanations, design calculations and real world troubleshooting support for students, hobbyists, and professionals.
Questions Answered with Practical Working Solutions
Backed by more than two decades of hands on circuit design experience, reader questions posted in the comments are reviewed and answered personally. Wherever necessary, circuit corrections, design improvements, and verified working solutions are provided to ensure accuracy and reliability.
How To Use This Website
- Start with the Electronics Tutorials section if you are new to circuit design.
- Explore application based projects to find ready to use circuits.
- Read the comments for practical tips, corrections, and reader discussions.
- Post your questions to get guidance and improvements where needed.
Learn Electronics Step By Step
Electronics Tutorials
Foundational tutorials explaining electronic concepts, calculations, and working principles in a simple and practical way.
Semiconductor Theory
Detailed explanations of semiconductor devices and circuit theory with practical examples and applications.
Arduino and Microcontrollers
Arduino programming tutorials and microcontroller based automation projects with complete circuit details.
IC 555 Timer Circuits
Classic and modern IC 555 timer circuits explained with calculations, diagrams, and application ideas.
Power Electronics and Energy Systems
Inverter Circuits
Designs that convert DC power into 220V AC with explanations ranging from basic to advanced sine wave systems.
Battery Charger Circuits
Controlled battery charging circuits covering lead acid, lithium, and industrial battery systems.
Power Supply Circuits
Fixed and variable voltage power supply projects for workbench testing and embedded applications.
Solar Controllers
Solar charge controllers and renewable energy projects using PWM, MPPT, and microcontroller techniques.
Application Based Electronic Projects
Home Electrical Projects
Electronic circuits designed to enhance safety, automation, and efficiency in home electrical systems.
Industrial Electronics
Control and automation circuits used in industrial machinery and process systems.
Automobile Electronics
Automotive electronic projects for lighting, safety, and performance enhancements.
Motor Control Projects
Speed and torque control circuits for DC and AC motors used in home and industrial applications.
LED and Lighting Projects
Decorative and functional LED lighting circuits including dimmers, chasers, and drivers.
Remote Control Circuits
Wireless and IR remote control circuits for convenient device operation from a distance.
Specialized and Utility Circuits
Wireless and GSM Projects
Wireless control and GSM based communication projects for monitoring and automation.
Meters and Testers
Hand-built electronic meters and testers useful for diagnostics and troubleshooting.
Timer and Relay Circuits
Delay timers and relay switching circuits for automation and protection applications.
Learning Through Discussion
A lot of the circuits here slowly get better through questions and discussions in the comments. Readers point out real world problems, ask for small changes, or request clarifications, and over time this back and forth helps turn the designs into more reliable and practical working circuits.
Try and Test Circuits Online
To help readers better understand how circuits behave, this website also includes a simple online circuit simulator. It can be used to visualize basic circuit operation, test component changes and explore circuit behavior before building it practically.
Recent Community Discussions
Latest questions, answers, and circuit improvements discussed by readers and the author.
Hi, yes half wave can be replaced with full bridge, but that is not required for simplicity sake...it still works…
Uchechukwu, by panel, do you mean the remote control relays? You can build that using the details provided in the…
Hi, I have been looking for a suitable replacement for a CDI box on my 1976 2stroke motocross racer. It…
Thanks Sir, but I want to make the panel on my own, is th at not possible? by the I'm…
To set this up, connect the power pin of the chip to your positive supply and the ground pin to…
Common Problems Addressed
- Circuits that do not work as expected after assembly.
- Confusion about component values and calculations.
- Improper power supply or overload issues.
- Noise, heating, and instability in practical circuits.
- Modification of existing circuits for custom requirements.
Note: All circuits are provided for educational and experimental purposes. Readers are advised to follow proper safety precautions while working with mains voltage and high power circuits.
Questions & Answers
hello goodmorning, goodevening, and good afternoon in anywhere you can saw this message, I’m one of this class and am glad to be here.
my greetings also goes to our boss may God bless him.
please sir I need a well drawn circuit diagram for inverter oscillator project with a voltage regulator. please 🙏 I will be so glad 😊 if I can have it.and that reminds me sir that the ic must be sg3524n or sg3525 ic
Good evening Michael,
If you search for “SG3525” in the top search box, you can get many good options which will fulfil your requirement…
hi sir,,it’s MdKen,,than you so much..
pls can you help me with a high end 9v powered 3band eq onboard preamp circuit design I can put in my ibanez sr505 bass guitar…I bought a it cheap but it was sabotaged …
the guitar uses 2 passive pickups
Hi Md.
You can try the first circuit from the following article:
https://www.homemade-circuits.com/10-band-graphic-equalizer-circuit-for/
For further doubts, you can feel free to comment under the above article..
On my old motorcycle, I’ve added a piezo beeper on each of the front turn indicators: that’s allows me to not forget them on. Puttin one on each was the easyest way to make it works.
I’ve done the same on my new one, but this new bike flashes the turn indicators to signal that the keyless system is engaged, resultin in a lot of noise.
What would be the simplest, smaller circuit to make a beeper sounds when one indicator is on, but not when both of them are on?
I think the easiest way is to use only one common buzzer for all the indicators, meaning if any of the indicators is turned ON, the buzzer sounds. This will also solve the noise issue during the keyless retry. What do you think?
I have a water pump bought cheaply at a nearby electronic stores. Its voltage and amp rating is not known but it runs nicely at 7.4V 3A. However, every time I need to start it, I need 16.8V to kickstart it and then I can run it with my 7.4V Li-ion pack. Is there any circuit that makes sure that the motor doesn’t need the initial 16.8V of power to start up and it can run with 7.4V throughout? Thanks in advance
Actually the pump is taking 16.8V kick just to break that initial tight motor friction. Best solution is put one cheap MT3608 or XL6009 boost converter module set to 16.8V, along with one simple 1-second delay relay or 555 timer circuit. So when you switch ON, then it gives 16.8V boost for just 1 second to kickstart the motor, then relay immediately switches line to direct 7.4V battery pack for normal running!
Is it possible you share the circuit diagram here
You can try this configuration:
I’m trying to modify this circuit a bit and am having issues. Look at Figure 18 here. (I tried to copy and paste but it wouldn’t work).
I need a low current draw flashing circuit.
I would like to replace LED1 with 3 blue LEDs in series (so 6 to 6.6V drop). I’d rather have them a bit dimmer than risk overvoltage failure.
I’ve built the circuit several times and expect I am toasting the IC chip.
I’ve been using a 1.6K resistor for R3. I expect this is the issue??
The LED’s are not blowing, but not flashing.
I built one circuit using fairly large variable resistors for R2 and R3. It works intermittently. It acts like it has a cold solder joint (yes I was building on a circuit board). Function depends on orientation of the board.
In my younger years this would have been a walk in the park.
I simulated your circuit with 12V and 3 blue LEDs in series with a 1k series resistor (R3) and it worked perfectly.
Please try changing the R1 to 18k, R2 to 150k, and C1 to 10uF, this will give you a flashing rate of around 1 second ON, 1 second OFF. If you find your 555 getting warm or hot at 12V, then definitely your 555 IC may be faulty or not the original make…
The chips I am using are definitely cheap knockoffs. 10 of them were $9. (10pcs ICM7555 General Purpose CMOS Timers Chips IC,DIP-8)
I wonder if that will be a problem.
10 nos at $9 is too costly for Indian standards, you can get original chips much cheaper than this in India…
However, if it is getting hot at 12V and LEDs at pin#3 with resistor, then certainly the ICs could be malfunctioning…
THANKS for your input.
I have a breadboard arriving tomorrow to build test circuits on (enough soldering things up to test).
I would prefer shorter ON time, and a slightly longer OFF time. This circuit is to simulate the flashing LEDs of a car alarm system.
The voltage will often be above 12V since alternators routinely put out up to 14V. Battery voltage while not running is normally above a true 12V, more like 12.5V. I don’t know what that would do to the values of components.
The low current draw was desired to not discharge the car battery over extended periods.
Sure, no problem….for the component adjustments, you can try the following software….Try to keep R1, R2, on the higher side, while the capacitor lower.
https://www.homemade-circuits.com/ic-555-timer-astable-circuit-calculator/
Good afternoon, Mr. Swagatam. Could you please post a circuit for connecting two lithium batteries for use on an electric bicycle with a hub motor? This would increase the range. When one battery runs out, the other one kicks in.
Thank you very much.
Hi Giuseppe,
Do you want the circuit with charger circuit, or only the batteries with a changeover stage? Please let me know I will quickly design it for you…
Can you introduce me to an FM circuit that I can implement in both ltspice and ctrl200? Thank you for your guidance
Sorry, I have no idea which FM circuit could be simulated on those simulators…however i think a BJT based design can be simulated on all standard simulators…
Which FM circuit are you referring to, transmitter or radio?
I’ve been asked to fit 3 remote leds to be fitted in parallel with existing 12v fuel gauge to indicate empty, half full, full. The supply voltage will be taken from the fuel sender unit. The value for the variable resistor in sender is 3 to 410 ohms.
Sure, you can add the LEDs in parallel with the existing ones through a series resistor whose value should be same as the existing LED series resistor’s value…
thanks for your prompt reply,i’ll give it a try
Hi again. I have two hydraulic valve packages, type Parker/Olsberg, with 4 valves in each package. Now I’m helping my friend. I built a signal control switch with a changeover relay for the electric control of the valves. The valves are controlled with current control. The problem is when I switch to the second package, the system protests that there is an interruption in the coils. So I have to restart the system again. I was wondering if I could change the relay to something else. Do you have any tips on some type of switcher.
Hi, I do not think the relay itself is the main problem. The controller is probably checking the valve coil current all the time, and during relay switching it sees an open circuit, so it gives the coil interruption error. You may need a “make-before-break” type switch, or an electronic MOSFET/solid-state switch that changes over without disconnecting the load. Can you tell me the coil voltage, coil current, and the relay type you are using? A simple circuit may solve the problem.
Thanks for your reply. Here are your wishes about my problem. The relay I use is from Conrad Finder 40.52.9.024.0001 2 pole alternating 24 volts 8 Ampere. Valve voltage is proportional 24 volts current is about 2 Ampere. The hydraulic valves are called Danfoss PVG 32.
Thanks for the details. I think the Finder relay is the reason for the problem. It is a normal break-before-make relay so during switching both valve packages are disconnected for a short moment. The Danfoss controller then sees an open coil and gives you the interruption error. I think you will need a make-before-break switching circuit, or an electronic MOSFET/solid-state changeover which keeps one valve connected until the other is connected. Another way could be to check if the Danfoss controller has a setting to disable the coil monitoring during switching. That may also solve the problem.
Do you have any alternative to another 2 pole changeover relay, possibly from Conrad? Greetings Göran
A 2-pole changeover relay is simply a DPDT (Double-Pole Double-Throw) relay. On Conrad, you can find them by filtering for “2 changeovers” (2 Wechsler).
Here are three alternatives they might have:
Finder 40.52 Series (8A rating, very common)
Omron G2R-2 Series (5A rating, industry standard)
Panasonic JW2SN Series (5A/8A rating, compact)
Just make sure to select the correct coil voltage (like 12VDC)
Merhaba Swagatam,
tek fazlı değişken frekanslı VFD örnek devreyi çanak vibrasyon makinelerinde kullanabilirmiyiz .yada bu gibi uygulama için önerbileceğiniz bir devre varmı.
Hi Aygun,
if your machine uses a universal motor (with carbon brushes) or a specialized single-phase motor designed for speed control, then a basic single-phase VFD circuit can work.
But for a satellite dish vibration machine which I guess is used for testing how the dish handles structural vibrations or stress….the best and most reliable approach is actually to use a 3-phase motor driven by a VFD with a single-phase input.
I need home automation circuit diagram that control fan, curtain and lighting system. Components values in each circuits. by using the following components: IR remote, power supply 12V DC, buck converter(12Dc-5Dc), IR receiver, ESP32, motor driver(12V Dc), Dc motors, zero crossing detector, opto-triac, triac,
Thank you…I have noted your request in the list, and will try to design it soon, once the other pending request are completed…
Hello everyone,
I’m currently working on a project to control curtains, fans, and lamps using a remote control system. My goal is to design a simple and efficient circuit that can wirelessly operate these devices.
I would really appreciate any guidance, especially:
A suitable circuit diagram for this kind of system
Recommended components (e.g., relays, microcontroller like Arduino, IR/RF modules, etc.)
Any tips on improving efficiency and safety
I’m still learning, so even simple explanations or references would help a lot.
Thank you in advance!
Hi, you can get all the required information on this page:
https://www.homemade-circuits.com/?s=fan+remote
For 800w 1000va (12 dc to 220ac volt) IPS Inverter circuit PCB , already purchased, how many N channel MOSFETs board shall be compatible ?
I have contacted you earlier & got satisfactory reponse.
I have an invention that you might be wondering about: Dolby sound with two speakers. Can you do it? I’m from Afghanistan. Can you support me?
Sorry, currently I do not have the circuit diagram details for this project…
The number of MOSFETs depends on the transformer current rating and the PCB design. For an 800W to 1000VA 12V inverter normally 4 to 8 N-channel MOSFETs are used, such as IRF3205 connected in parallel.
If your PCB already has fixed MOSFET positions then you should use exactly the number supported by the PCB layout and heatsink arrangement.
I’m wondering if you can help with a problem I would like to solve. I built a small inverter for a vintage radio to replace a B battery 90v . The inverter used 4047 ic and IRF540 mosfets.The radio works extremely well with no EMS. My problem is to use a circuit to automatically shut down the inverter when the radio is turned off, saving battery life. I had a look at one of you designs which used 4 x BC547 and a replay, which I have yet to build. Space is also a problem as some radios have a very small area . I tried a LM358 with 10 ohms in line with the output for current sensing. The problem with it was that the output and input have a common earth which destroyed the IC with 90v on one input. Can you make any suggestions please ? Regards Rudy
Hi Rudy, you can solve this more simply by sensing the inverter input current instead of the 90V output side. The LM358 failed because its input pins cannot tolerate such high common-mode voltage.
A compact method would be to use a small PNP transistor or BC547 relay driver connected across the radio ON/OFF switch or inverter supply line. When the radio draws current, the transistor keeps the inverter enabled, and when the radio is switched OFF the inverter also shuts down automatically after a short delay.
You can also try a reed relay or optocoupler method if isolation is required. Avoid direct sensing on the 90V line with ordinary op-amps.
I’m very grateful for your reply, thank you.
Am I able to send the circuit diagram that a member of our Historical Radio Society designed for comment ? He has a copyright on the auto on/off which I can’t morally and won’t legally copy, it is very effective in it’s operation. If I could achieve the same results I could build about 6 of them for my AC/DC radios. I have no intention to build or sell them commercially. Failing that is there any chance of you helping me designing one with a 6-9v input maximum output of 90v ?
I have built the inverter which works very well, I’m using a 9v to 2 x 120v toroidal transformer.
The transformer is “potted” in an epoxy compound within a plastic housing. Configured with 2 x 120V primaries and 2 identical secondaries which can be wired in either series or parallel.
Specifications
Sec. V: 9+9
Sec. Parallel: 1.1A
Sec. Series: 0.5A
Primary voltage: 2 x 120V AC
Total VA rating: 10VA
Insulation: Class A (105°C)
Magnetizing current: <20mA
Temperature rise: <65°C
Recommended AC Fuse: 100mA
Regulation: ˜20%
Sure, I understand the situation, let me try it, I don’t think it would be difficult for me.
However, the description of the switching pattern suggests that the inverter can never be ON if the radio is OFF. Meaning once the inverter is turned ON, the inverter will check if the radio is also turned ON or not, if not it will simply switch OFF permanaetly,…is that correct??
That is correct, it works extremely well.
OK, thanks, here is the schematic which you can use to solve the application requirement. The Relay coil voltage rating will be same as the battery voltage rating:
I built it and it didn’t work. Could please explain how it’s supposed to work and specifically where the 22k connected . You say the 90v supply , is that on the output of the inverter ?
The +90 Volts comes from the radio supply after its switch is turned ON. If the radio switch is OFF, then there should be no +90V available at this 22k input of the transistor. In this situation, if the push button is pressed/released the transistor will remain ON for a couple of seconds through the charge stored inside the 100uF capacitor, and then auto turn OFF the relay and the inverter.
If you press/release the push button again, the same incidence will keep repeating as long as the radio is off (+90V missing at the input of the 22k end). If the radio is ON, then the +90V input will feed the transistor base holding the relay permanently ON, as long as the radio is ON…
The push button is a momentary push to ON switch, meaning it turns OFF as soon as the finger is removed from it.
This circuit is a straightforward design and should start working immediately as intended by you.
Let me know if you still have problems with the circuit…
Thank you for your explanation, very helpful. I will try again possibly tomorrow.
Thank you for all the trouble you’ve gone to, I shall build it today and let you know
Sure, no problem at all….let me know how it goes.