Working with 230Vac

Your reference guide to working with 230Vac or 110Vac High Voltage Electricity.

Edited by Lim Siong Boon, last dated 29-Aug-09.

email:    contact->email_siongboon  



Content 230Vac

  1. Safety

  2. Signal and Measurement

  3. Working with 230Vac electronics

  4. AC lightings wiring guide




1. Safety  

















The objective of this site is to get to know about the electronics components that can help us control 230Vac devices. Devices like ac lamps/lightings, power sockets/supply, heater, and many many other appliances at home. We are all surrounded by many appliances operating directly from AC mains supply. It is very interesting to control and work with these appliances. Learning to control with electronics, microcontroller and computer.

Our home is typically pre-installed with 230Vac sockets. The socket where we obtain our electrical power source. It is this basic utilities that keeps us operating in this urbanization era. Different country implement their own AC voltage system & AC plug. The electrical delivered to our home wall socket is a 230Vac single phase ac power. So throughout the section, we will only talk about single phase system and not the three phase system.

The first thing in my mind when it comes to 230Vac is "Dangerous"!!! I am still very scare of it. One careless mistake and we might not have a second chance to try again. Some article suggests that a voltage over 30V is considered as danger. Lower voltage is relatively safe to touch with your bare hand, although sometimes you may get the shock sensation on your muscle.

230Vac is a dangerous stuff, but when working with electronics you can hardly avoid using it. And when we cannot avoid it, then we have to face it. Facing it, by understanding more about it. Minimizing our chance of getting killed by 230Vac. So let us pay careful attention to this section.


The following article is from a website with simple illustration of electrical safety. It explains in simple terms the difference between birds and human touching the same high voltages cable. Why birds don't get electrocuted? How do we get electrocuted? From these two question, we get to understand more about voltages and how we should deal with them to protect ourselves. Safety first, which is why I put this as the first section.

- electrical safety.pdf

Remember that we will not have any chance to try again. Understanding the danger of electrical earth path will minimize the chance of getting electrocuted.

Before touching any wire, be sure to measure and ensure that there are no "live" voltage on the wire. You can use a multi-meter or test pen to check for live connection.

Multi-meter. Measure between the "live" and "nuetral" line to check if 230Vac is present.


Test Pen (this test pen comes in the form of a slotted screw driver. You can see a small bulb embedded in the handle. Touch the suspected "live" wire with the tip of the screw driver. Locate the back of the handle for a metal plate. If the bulb inside the handle lit up, when you touch your finger to the metal plate, it means that the wire is "live".




Electrical System around the world,


Electrical Safety,

- or electrical safety.pdf


Electrical box install at home..         .

Bigger electrical box install at office...


Various names: Electrical box, DB box, Electrical distribution panel, Control panel


On the left are some of the common electrical box that we may find in our home. They are the main electrical distribution point to all the other rooms. From the power station to the sub-station and then to this box, distributing electrical power to our rooms.

This Type-G plug distributed to our rooms, consist of 3 cable namely Live (hot, brown), Neutral (return, blue) and Earth (safety ground, yellow/green).

Click here for other plug type.



On the electrical box, we can see a row of switch. One main switch is particular unique in color or size. This is the main switch which cut off the supply from live and neutral wire. The rest of the switches, only the live wire is disconnected. This is an important note to take, and the same applies to the wall switches. When we switch off the light or appliances, only the "Live" wire is disconnected.

There was once I was working on a power supply unit. Wanting to doing rewiring, I switch off the power leaving the 3 pin plug on the socket. I have carefully unscrewed and pull out the earth wire. Thinking that it is now safe that I have switch off the AC socket, I become relax and casually removed the earth cable. The earth wire accidentally touches the neutral wire and phow, my whole office got black out. From then on, I remember that neutral wire is as alive as the live wire. Never treat it lightly. When you switched off the power to do maintenance work, do not assume that the live as well as neutral is disconnected. Always check and handle them with care. Insulate the bare wire if you are unsure. Assume that they are always alive, unless you are absolutely 100% sure that the wire is unplugged from the power system. 99% is not good enough. It has to be 100%.


MCB (miniature circuit breaker) to protect the electrical line from over current drawn. RCB (residual current breaker) similar to MCD is another protection device trips when electrical leakage is detector (incoming current != outgoing current). Some device has both the features of MCD & RCD. They normally comes in the standard DIN rail mounting for the electrical boxes.

Other name: ELCB, MCCB, RCD, RCCB, RCCD (residual current circuit breaker), ground fault circuit interrupter (GFCI), ground fault interrupter (GFI) or an appliance leakage current interrupter (ALCI), safety switches, "salvavita" (life saver).





Power Distribution Components, MCB, RCB, Switches




It is recommended to install a circuit breaker (MCB) as well as a residual current breaker RCB when working with AC devices/equipments under test. They can protect against accidental over current or leakage fault that occur. Anything goes wrong, the device will be tripped, cutting off the power supply from the mains, protecting us from possible electrical shock.

RCB is more important as a protection from serious electrical shock. During normal operation, the current to and from the live and neutral wire should be equal. Any different in current indicates leakage. The device detects the leakage and trip the supply source.

MCB is more to cut off supply on overloading load. Example would be a short circuit from a faulty equipment. If the supply is not cut in time, the huge current pumping through will heat up the cable, resulting in fire along the cable.

There was once I am working on an automated swing door system. I try to cover back the aluminum cover, but find difficulty putting it back in position.  Not knowing why there was this small gap, I bang on the cover trying my luck to close it up. Suddenly I felt a very loud bang and bright light flashes over me, followed shortly by a slight breeze. They were the result of the small explosion.

After investigating, I found out the the casing actually cuts through the AC cable resulting in a short circuit. The cable were not properly secure in a safe position and the cover finishing is badly done. The edge will not filed and has a very sharp edge. It is lucky that I remembered to connect the earth wire to the aluminum cover, else I would have being shocked. So as you see, it is important to earth the metal surface that are near the AC line.

The MCB is found to be tripped, and some burn mark can be seen around the place of impact. The MCD is trip almost instantly, but the 3 pin AC plug for the automation door is still badly burned. When I open up the plug, the interior is completely burned out. Wire and fuse all black with carbon. I have to spent another hour to repair the cable & plug, tied the cable in place, smoothen the cover edges. A lesson to learn. Proper installation not only protects ourselves and it also minimize re-work.

In this scenario, the earth wire and MCB have done their job very well. You may have installed these protect in place, but without proper knowledge of how they are going to protect you, you are just as vulnerable. Learning how to protect yourself is the most important.

   A normal electrical switch. (no protection function)



     lockable switch for tagout purpose


The switch on the left may looks like MCB or RCD. It function as a simple single pole switch, and offers no protection at all. They are typical used to disconnect the live wire inside the electrical box, switching off the devices just like a wall switch.


Some models comes with a lockable design, for user to tagout. This is to minimize any chance of people unknowingly switch on the power, when the user is doing the maintenance work.

mcb-single-pole-b10-b16-c10-d10.jpg Single Pole MCB explain Curve Types

Surge current can be higher than steady state current, especially for inductive/capacitive load. Eg. motors. The surge higher than the current limit set, can easily trip the MCB. This means that it can be difficult to switch on a motor for example, because a surge from the motor startup can easily trip the circuit breaker.

This call for special MCB which has a wider allowance for surge current. MCB comes in various curve type, each has its torlerrence for surge current.

The photo on the left shows 3x MCB type (red color lever) having a circuit breaking current of 10 amphere, namely B10, C10, D10. Each of them has the same current limit. The type B, C or D curve indicates their ability to withstand sudden power on surge current.

MCB type B curve - Can withstand a surge current of about 3-5 times its rated current limit. For this MCB B10, the rate current limit is 10A. So this means that the MCB can withstand up to about 30-50A of surge current within the initial millisecond time.

MCB type C curve - Can withstand a surge current of about 5-10 times its rated current limit. For this MCB B10, the rate current limit is 10A. So this means that the MCB can withstand up to about 50-100A of surge current within the initial millisecond time.

MCB type D curve - Can withstand a surge current of about 10-20 times its rated current limit. For this MCB B10, the rate current limit is 10A. So this means that the MCB can withstand up to about 100-200A of surge current within the initial millisecond time.

There is another single pole MCB B16 in the picture. This MCB breaks the circuit when the current is over 16A. The MCB is of type B, meaning it can withstand the initial surge current of about 48-80A.



Industrial safety practice

When servicing AC socket or equipment, ensure that the AC source at the electrical box is switched off. If possible, unplug from the AC socket.

Lockout/Tagout procedure should be practice strictly. This is important when we work outside because we may not be the only person operating the equipment. Lockout/Tagout involve locking and tagging the switch source. So you can be sure that no other people can switch the power back on, when you are working on the socket or equipment. It is a safety procedure. If you do not have the facilities to lock out the power, a sign board or labeling warning is advise to prevent any accidental switched on.

For your own safety, the procedure is worth the trouble.

Some signage references,
As what I have experience, AC power is actually quite dangerous. It is very important that you equip yourself with the knowledge and know-how to protect yourself against any electrocuted accident. Safety is the most important. Always treat it as through it is the first you have touch it., Singapore Network Ethernet WiFi RS232 RS485 USB I/O Controller

Singapore Customized, custom made Electronics Circuits & Kits



2. Signal and Measurement


graphic taken from:




graphic taken from:



Measuring Voltage

There is once I wanted to measure the AC signal using my oscilloscope from the mains. I am curious to look at the sine wave from the wall socket mains. Tack, all the offices around me had their power tripped.

I made a Mistake?.....  I don't even know why? I was lucky that I took extreme precaution during the measurement.

It is then that I started to re-visit 230Vac to understand more about it. I realized that our oscilloscope ground clip is actually connected to the earth as reference. Which is why the power trip, when I clip the ground lead to the neutral line. When this earth clip touches the neutral wire, the extra electricity leakage tripped the MCB (Miniature Circuit Breakers) found inside our electrical box. This is a safety feature to protect us. So remember that the Earth line is connected to the ground lead of the oscilloscope probe. Be careful.


Does this means that we cannot measure the ac waveform using the oscilloscope? How do we do the measurement then?

From what I found out, there are various methods to measure. Differential method to measure the AC signal would be more appropriate. Two probe would be required, placing across the signal you ant to measure. Ground lead can be floating, which the reference is earth because the ground lead is connected to the earth line. The difference between the two probe channel would be the actual AC signal. With help from the typical oscilloscope feature, the signal can be obtain as a single waveform ploy on the screen. One of the channel need to invert (using the INV function), and both the channel are added (using the ADD function).

Measurement technique

- A Shortish Guide to Using an Oscilloscope.pdf

- Floating Oscilloscope Measurements.pdf

- Fundamentals of Floating Measurements and Isolated Input Oscilloscopes.pdf

- (10x probe to measure high voltage)




Oscilloscope guide from other site,

- XYZs of Oscilloscopes, Tektronix 03W_8605_2.pdf

- Basic oscilloscope operation.pdf-



Seldom typical engineer like us need to examine the AC signal. Those power engineering people who wanted to measure the signal probably wanted to see the harmonics to check up on the quality of the power supply. Or perhaps, as curious as I am, just wanting to see it.

Measuring the mains using digital multimeter. Reading is 230Vrms

graphic taken from:




The waveform of the AC mains 230Vac 50Hz is shown in red.

The signal we should see on the scope.... (click to enlarge)



The most frequent used equipment for measuring our 230Vac mains would be the multi-meter. Portable and inexpensive. Providing us the basic measurement for checking the wire voltage. The power is quite reliable in urban area, always maintain it's voltage reasonably at 230Vac. Probably a test pen can be the only measuring equipment you need.

When we measure the ac mains from the socket using the digital multi-meter, we will get a reading of 230Vac or 110Vac (depending on the country you are in). Take special  note that this reading is effectively the rms (root mean square) voltage. The actual peak voltage of the electrical line go up to about 325Vpeak. The 325Vp (peak) sine wave is equal to 230Vrms.

Vrms = √2 x Vp.

230Vrms = 0.707 x 325Vp.

Vrms can be think as the equivalent voltage in dc for power computation. The actual AC power (sine wave in red) has the same energy as one that is illustrated in the Vrms view point (square wave in blue). The energy can be computed, and they are defined as the area under the waveform. Area under the square & sine wave is equal. I have draw out the waveform to illustrate the idea.

Keep in mind the peak voltage. It would be useful in helping you select the proper component. Capacitor is one of such component where the capacitance and voltage rating is the main criteria for selection. Voltage higher than what the it can take, the capacitor will experience voltage breakdown. Pop, the capacitor can have a mini exposion.

So do remember, the AC mains is in fact 325Vp (peak) or 650Vp-p (peak to peak). That is very high voltage!!!










The Practical Part.........

Yes. Now that we get our theory clear, let's get on to the real hands on.

Date: 2009-08-01
This is one of the most exciting experiment that I ever done. Ever since my first disaster measuring AC mains, my understanding of oscilloscope and AV mains remains very unclear. Every step is carefully think of, carefully executed. This is unlike any other new electronics circuit that I want to experiment with. Any minor doubt that I have, I will research on the internet to confirm my understanding before I connect up the circuit.

It feels to me like experimenting with dangerous explosive. One mistake, either my life at risk, or my expensive digital oscilloscope gets damaged. It is the most detailed experiment that I ever done.

For an experience engineer, this can be as easy as ABC. For a first timer like me who have never measure the 230Vac line, and no senior to guide me, this is really frightening yet exciting. I am sure we will have a better understanding of high ac voltage, with this step by step measurement guide. Dealing with 230Vac will eventually be as easy as ABC.

So let me starts this exciting experiment.


NOTE: Click on the image for a clearer view.


My measurement setup for measuring the output of the zero crossing triacs circuit. A detail connection of this setup is shown in the following section.


The picture on the left is the setup that I have prepare for the 230Vac signal measurement.

Equipment used in this measurement experiment

- 3 pin extension socket (protected by RCD device)

- Triacs switch circuit

- DC power supply (to activate the triacs circuit)

- AC fan (device to be controlled by the switch circuit)

- Oscilloscope (Tektronix TDS 2014) and probe.

- Some wires for connection.



My triacs switch circuit. This switch circuit is solid state relay. Just like a mechanical relay, the circuit interface helps digital control circuit to control a 110/230Vac mains devices. There is a AC input and the controlled output as shown by the green wire terminal. Click here for further detail information on this circuit on another page.


Probe ground crocodile clip is clip onto the oscilloscope Earth pin. The measurement for Live/Neutral signal is with reference to the Earth potential.


The circuit that I am going to measure is the output of a AC switch circuit presented on the left. The circuit using a triac component to switch the AC power. If you are interested to find out more about this circuit, you can visit the following page I have put up.

- about Triacs circuit

The following summaries the steps taken in order to do a proper measurement.

1) All the equipment for the experiment is powered from the RCD (residual current device) protected extension plug. This is to protect myself in case I accidentally touches the live/hot wire. The RCD will cut off the power in the case of power leakage through my body.

2) Connect up two probe from the oscilloscope to the circuit. CH1 probe is connected to the Live wire output, while CH2 is connected to the Neutral wire. The ground clip of the probe should be connected to the oscilloscope Earth pin. You should able to see such a pin on your scope with the Earth/Ground symbol (see the photo on the left). This is the setup for measurement with reference to the Earth ground. This Earth pin is internally connected to our 3pin AC socket. Therefore the pin is the same as our 3 pin plug Earth. The grounding clip from the oscilloscope is found to be Earth, so in fact there is no need to connect up. For clarity and safety reason, just connect it up. Always ensure that your oscilloscope is properly Earth for safety reason.

3) Set the probe attenuation to 10x. On probe there is a switch labeled 1x and 10x. 1x means that the probe signal is exactly feed into the scope. 10x means that the signal will be attenuated to a factor of 10 times before feeding into the scope. The scope may not be aware of the attenuation, so it is important to setup the scope for the 10x measurement. If this is not done, you will find that the reading is 10x smaller than expected. A 10V signal will be read as 1V. It is not important but will be clearer if you just set it on the scope. The signal is expected to see on the scope should be a 325V. After attenuating the probe, only 32.5V is actually feed into the oscilloscope input. Tektronix TDS 2014 oscilloscope can accept signal up to 300V. Without the attenuation, the scope might just blow up. Although the scope received only an input of 32.5Vp, it multiple the scale by a factor of 10 because of the settings I have done on the scope.

4) The reading is going to be very high, so set the voltage div for both CH1 & CH2 to the max. In my case after adjustment to the 10x factor on the scope, my max setting is 50 volt/div.

5) Set the scope to Math function: CH1 - CH2. CH1 is measuring the Live signal with reference to Earth while CH2 is measuring the Neutral wire with reference to Earth. In order to measure the signal Live with reference to Neutral, we need the scope to do some math, CH1 - CH2. (A red trace appear representing a new trace CH1 - CH2). Disable the CH1 & CH2 trace so that you can see only CH1 - CH2 trace clearly.

6) Ensure that all wire is properly screwed and secure. Pull individual wire, and ensure that it does not comes off.



The oscilloscope presents the signal at the output of the triacs switch circuit.

The AC mains power is not switch on to the triacs switch circuit yet, so no signal is detected at the circuit output..

Once I switch on the mains switch, some small noise is detected at the output of the circuit. The triacs is in the off state but some signal is being observed. This means that there are some leakage. The leakage is ok because it is too small to activate the AC fan.

The triac switch is activated and the 230Vac is observed at the output. Yes, this is the 230Vac. But there is a problem. The voltage is too high for the oscilloscope to display. My scale is to 50 volt/div, and I have only 8 division on the y-axis for display. This means that I can only measure in the range of 200Vp-p. The reason for the signal clipping on the display.

To display the full 230Vac range or 325Vp-p. We need to attenuate the signal more. Some probe you have the option to attenuate by 100x.


230Vac measurement connection with oscilloscope


Measurement with voltage divider across Live & Neutral wire.


My probe only allows me to attenuate the signal by a factor of 10. I will need to attenuate the signal further.

For my case, I have a voltage divider using 2x 1MΩ (0.25W), to attenuate the signal by two times before feeding the signal to the probe. The voltage divider is connected across the output terminal of the Live and the Neutral wire. CH1 is connected to the divided voltage (between the two resistor), while the CH2 remains connected to the Neutral wire.

You can use other resistor value but you need to ensure that the resistor wattage is able to handle the high voltage. The maximum voltage across the Live/Neutral is 325V. If 2x 1MΩ is used for he voltage dividing, the maximum current expected will be about 0.16mA. The minimum wattage required is therefore 325V x 0.16mA = 0.053W. I have used a 0.25W resistor, which is more than enough. If you are using 2x 10kΩ resistor divider, make sure your resistor wattage is at least 6W. There will be more current flowing through the resistor, more energy dissipating across it, and it is going to be hot. A lot of energy is wasted if you use lower resistance.

The left present the actual measurement setup with a voltage divider circuit to attenuate the signal so that the oscilloscope is able to display the high voltage.

Remember to multiply the voltage by 2 times while you analyze this waveform. This is because the voltage has been divided by 2 due to the voltage dividing circuit. Click on the photo to enlarge the signal 650Vp-p at 50Hz, representing our 230Vac mains supply.

Finally a clear 230Vac waveform display with a period of 20ms. I finally managed to measure the 230V mains.

On the scope, the signal display about 320Vp-p, but in fact the signal is actually about 640Vp-p. This is because of the voltage divider that I have added and the scope just have no idea about it. So mentally, you need to multiply by 2 to get the correct reading. This is about the same as what we have computed previously. 230Vrms has the actual waveform of 650Vp-p at 50Hz. Any capacitance component attached across the Live & Neutral wire have to withstand at least the voltage of 325V. This is important for our component selection.

After this write up I have better confidents in dealing with 230Vac and it's electronics. Something that I often used and understood little about it.

It is so interesting. If only I am as curious when I am in school during my teenage days. There would be many teachers to guide me in the understanding. As a teenagers, most of us probably be fooling around rather than learning seriously and actively. Wanting to learn and know more than what the lecturer teaches.

I hope you have enjoy, and get a better understand in dealing with 230Vac measurement.


Measuring current by inserting the meter into the current path.



Measuring the AC current using the clamp meter. Easy, just clamp it.






picture taken from:

Measuring Current

How much current is being drawn from your wall socket. You might probably want to know how much energy your equipment/appliances is consuming.

For measurement of current, a cable clamp meter is recommended. Clamp measurement detects the invisible alternating electrical field generated by the 230V ac 50Hz. No contact with the copper wire, just clamp around the cable. This is all about Faraday Law, founder Michael Faraday. It is actually very interesting learning about the history of how people actually discover these physics. They are great people. I watched a very interesting science history documentary. A documentary about the history and concept behind E=mc2. I think it would be great to share you everyone.

Do a search on,

"E=mc2 - Einstein and the World's Most Famous Equation"




a mini current sensor for AC power line. Comes with 1:300, 1: 500, etc... transformer coil ratio

Measuring Current using a current sense coil or transformer

The picture on the left is a mini current transformer. To measure the current flowing through your AC power line, either a "Live" or "Neutral" wire has to be put through the hole located in the centre of the sensor.

The sensor consist of fine wire coil inside. The coil is wind around the circular core, forming a ring to sense the AC magnetic field around the AC power cable through the hole. It is important that only the "Live" or "Neutral" wire can be inserted through the hole. If both the "Live"and "Neutral" are put through the hole, the signal will be minimum. This is because the magnetic field of the out going wire will be cancel off by the returning wire.


The picture on the left is a simple setup with the oscilloscope probe to the two terminal on the current sensor.

Note that only 1 wire (Neutral) through the hole on the current sensor.

Signal at the output of a 1:300 coil transformer, while powering up a sprindle motor. The motor load is an inductive load. The current signal being pick up is quite noisy from the motor. The signal is about 5Vp-p.
Signal at the output of a 1:300 coil transformer, while powering up a soldering iron. The soldering iron is a heating element which is a resistive load. The current signal looks like the 230Vac 50Hz sin wave at about 0.2Vp-p.

This is a rectified signal (using diode bridge) picked from the sensor. The power line is not powered up, no load. I thought it should be flat. It could be noise generated from other nearby appliance through the "Neutral" wire.

The signal seems weird, but I did not investigate much on this result.

Ch1 is the rectified signal picked up by a 1:300 current sensor. The motor load is being switched on and off.

Ch2 is the signal conditioned through a LPF (low pass filter) and an op-amp comparator circuit. A clean result showing the motor being on and off.

Ch1 is the rectified signal picked up by a 1:500 current sensor. The motor load is being switched on and off. As you can see, the magnitude of the signal being picked up is higher. A higher voltage output, is being trade-off with a lower current drive. Since the signal will be conditioned by an op-amp, having a low current drive is not much of a problem.

Ch2 is the signal conditioned through a LPF (low pass filter) and an op-amp comparator circuit. A clean result showing the motor being on and off.





Computing Appliances Electricity Usage

Now that we measured the current consumption, I am starting to be curious on the power consumption for a typical home. Just for the fun of it, I have investigate some of the high power consumption appliances.

Energy (Wattage) = Voltage (Vrms) x Current (Ampere)





Energy meter to measure power consumption of your electrical appliances.



How much does my power cost?

Energy cost: S$0.1803/kWh as on 16 Jun 2009

Energy cost: S$0.2558/kWh as on 1st Apr 2011

Energy cost: S$0.2728/kWh as on 1st July 2011

This means that it cost S$0.1803 running an appliance consumption 1kW  for an hour.


See more energy measurement at another webpage Energy Audit


Air King Model 9106

Energy: 57-77Watt




Energy consumption for 8hr/day= 77W x 8hr = 616Wh

Energy consumption for 30 days = 616Wh x 30 = 18.48kWh

Energy cost for 30 days = 18.48kWh x $0.1803/kWh = $3.33

Energy for a Fan will cost about

$2.47-$3.33 per month




         Daikin Inverter Multi Split (R-22)

Energy: 1520-6900Watt


MSZ-FB series

Energy: 2500-5000Watt


Energy consumption for 8hr/day= 6900W x 8hr = 55.2kWh

Energy consumption for 30 days = 55.2kWh x 30 = 1656kWh

Energy cost for 30 days = 1656kWh x $0.1803/kWh = $298.58

Energy for a Fan will cost about

$65.77-$298.58 per month







MR-560U 560 litre Refrigerator

Energy: 570kWh/year

or 65W when I divide that number

with 365 days x 24 hours



Energy consumption for 8hr/day= 65W x 8hr = 520Wh

Energy consumption for 30 days = 520Wh x 30 = 15.6kWh

Energy cost for 30 days = 15.6kWh x $0.1803/kWh = $2.81

Energy for a Refrigerator will cost about

$2.81 per month



Philips MASTER TL5 circular fluorescent lamp

Energy: 22-60W


Philips PL-T compact fluorescent bulb

CFL, compact fluorescent

Energy: 32-42W


Energy consumption for 8hr/day= 60W x 8hr = 480Wh

Energy consumption for 30 days = 480Wh x 30 = 14.4kWh

Energy cost for 30 days = 14.4kWh x $0.1803/kWh = $2.60

Energy for a fluorescent lamp will cost about

$0.95-$2.60 per month


Energy consumption for 8hr/day= 42W x 8hr = 336Wh

Energy consumption for 30 days = 336Wh x 30 = 10.08kWh

Energy cost for 30 days = 10.08kWh x $0.1803/kWh = $1.82

Energy for a fluorescent lamp will cost about

$1.38-$1.82 per month


Incandescent Light Bulb

Energy: 50W



Incandescent seems to have similar wattage with the fluorescent. In fact a 15W compact fluorescent can have the equivalent brightness of the 50-60W incandescent bulb. Therefore using fluorescent can be cost saving.


  The energy cost matches quite well with my home monthly electrical bill. I am quite surprise that the fridge use so much less energy. Did I make any wrong assumption? Now I also aware that the energy to turn on the aircon for a day, is enough to operate a fan for 3 months.










End of the fun. Let us start to research more about the AC ingredients available.


See more energy measurement at another webpage Energy Audit
, Singapore Network Ethernet WiFi RS232 RS485 USB I/O Controller

Singapore Customized, custom made Electronics Circuits & Kits



3. Working with 230Vac electronics  
Component suitable for switching on and off 230Vac devices.

- Mechanical relay

- Solid state relay

- Triacs

- Thyristor

- Capacitor (high voltage rating)

- Resistor (high wattage rating)

- Transformer


about transformer- transformer.pdf

reference from


The list on the left are namely some of the common components used for controlling 230Vac appliances.

This section is closely related to switching. So I decide to divert your attention to the switch. The range of components for controlling your appliances. It is all about "Switch"...

So let's move on to learn more about switch.



AC to DC conversion (Transformerless)

Our electrical system uses high AC voltage to distribute energy to our homes. Most gadgets works with DC voltage, therefore we often see a AC-DC circuit module as part of the gadget.

Some AC-DC module are integrated into the product; for example, our computer, DVD player, radio. Some AC-DC module comes in the form of power adaptor that supply DC voltage to the devices.

The AC-DC module is so common, it will be useful to learn about them. Most AC-DC contains a transformer to isolate the DC voltage from the AC mains. This acts as a form of protection, so that people will not get electrocuted when touching the DC circuit.

There is also a newer type of AC-DC using switching method. It is something similar to switching DC-DC method. The transformer used can be alot smaller. You can see that old power adaptor was heavy and bulky. The power adaptor nowsaday are light and small.

Another type of AC-DC module uses only resistors and capacitors, without any transformer. They are also known as transformerless AC-DC circuit. You need to be careful when handling this type of cicuit as it is not isolated from the AC mains. You will get electrocuted touching the DC circuits. Please refer to the section above to understand more about 230Vac and how one can get electrocuted. Transformerless circuit is simple and cheap, and it is suitable for application that consume low power.



Example:  Transformerless 230Vac to 4.6Vdc


Please click here to see the transformerless AC-DC circuit schematic.



This circuit converts 230Vac to 4.6Vdc without using any transformer. Please take note that the circuit is not isolated from the 230Vac mains; ensure that the circuit is enclosed and properly earthed to prevent accidental electrical shock.

(Last update: 31 Oct 2010)

Example:  Transformerless 230Vac to Vdc (for a load of 24Vdc 20mA)

Please click here to see the transformerless AC-DC circuit schematic.


ac-dc transformerlessac-dc transformerless


This circuit converts 230Vac to Vdc suitable for a 24V 20mA load, without using any transformer. Please take note that the circuit is not isolated from the 230Vac mains; ensure that the circuit is enclosed and properly earthed to prevent accidental electrical shock.

(Last update: 12 Jan 2011)

Another transformerless circuit 230Vac to 5Vdc that I found on the internet. (I have not tested this yet)

AC-DC integrated circuit product manufacturer

You can refer to the datasheet on their website for the datasheet and application notes.

power integration

High efficient ac-dc conversion IC

- isolated (smaller transformer component)

- non isolated (transformerless), LNK306DN

2018-10-31 Transformerless Power Supply - 230Vac to 12Vdc



ST microelectronics

- isolated (smaller transformer component), VIPer12A

AC-DC switching IC
IC: LM5021
IC: IRIS4013(K), IRIS40 series, irismps3.pdf
IC: NCP1200, AND8023-D.PDF
IC: NCP1215, AND8128-D.PDF
IC: NCP1271, AND8242-D.PDF
IC: NCP1381
IC: NCP1603, AND8207-D.PDF, Singapore Network Ethernet WiFi RS232 RS485 USB I/O Controller

Singapore Customized, custom made Electronics Circuits & Kits



4. AC lightings wiring guide  
Keyword: difference between normal fluorescent, PLC lamp
LEd fluorescent circuit
power supply LEd fluorescent circuit

Connecting electronic ballast with a fluorescent lamp.


Say hob 32a
Say oven 32a

Total load 64amp

Cooker apply diversity

1st 10a 10amp
30% of 54a 16.2amp
Allow for socket 5amp

Ib 31.2amp
(Ib no socket 26.2amp)

Pluggable connector for 230Vac lighting points (Live, Neutral, Earth)


SPINNE EM16 connector (Black)

SPINNE EM16 connectorSPINNE EM16


163 3 TS IEC998-2-1 connector (Black)

163 3 TS IEC998-2-1

163 3 TS IEC998-2-1163 3 TS IEC998-2-1

163 3 TS IEC998-2-1

Can be purchased from New Starlight Industries Pte Ltd



quick release wire connector quick release connector (no need to screw on the wire)

Pluggable 3 way connectors from wieland, commonly used for connecting electrical AC cables to lightings lamp. The connector can be pre-installed onto the power termination point and the mating connector on the lamp component. This simplifies the cable to lamp connection and allows faster installation.

5. Ground Loop

references:, Singapore Network Ethernet WiFi RS232 RS485 USB I/O Controller

Singapore Customized, custom made Electronics Circuits & Kits



Keyword: Vac mains, 230Vac 110Vac, High Voltage, Electrocute, Danger

Wall sockets, power points, power sockets, electric receptacles, electrical outlets

email:    contact->email_siongboon