Arduino Dimmer for Lamp

Simple AC PWM Dimmer for Arduino

Here we have designed a PWM dimmer circuit which uses IRF830A (N – CHANNEL 500V – 1.35Ω – 4.5A – TO-220 PowerMESH MOSFET) in a diode bridge used to control the voltage across the bulb with pulse-width modulation (PWM). The power supply voltage for driving the gate is supplied by the voltage across the MOSFET.

By using this project you will be able to control the brightness of a lamp connected to the circuit through serial port.ie the brigntness can be adjusted depending on the commands that we pass through serial port.In this project the following will be the serial port commands that we will be using.

• ‘0’ to Turn OFF
• ‘1’ for 25% brightness
• ‘2’ for 50% brightness
• ‘3’ for 75% brightness
• ‘4’ for 100% brightness

Circuit diagram and description

The power supply voltage for driving the gate is supplied by the voltage across the MOSFET. D6, R5 and C2 form a rectifier. R5 limits the current pulses through D6 to about 1.5 A (as a consequence it is no longer a pure peak rectifier). The voltage across C2 is regulated to a maximum value of 10 V by R3, R4, C1 and D1. An optocoupler and resistor (R2) are used for driving the gate.

 R1 is intended as protection for the LED in the optocoupler. R1 also functions as a normal current limiting device so that a ‘hard’ voltage can be applied safely. The optocoupler is anold acquaintance, the CNY65, which provides class-II isolation. This ensures the safety of the regulator. The transistor in the optocoupler is connected to the positive power supply so that T1 can be brought into conduction as quickly as possible. In order to reduce switching spikes as a consequence of parasitic inductance, the value of R2 has been selected to be not too low: 22 kΩ is a compromise between inductive voltages and switching loss when going into and out of conduction.

An additional effect is that T1 will conduct a little longer than what may be expected from the PWM signal only. When the voltage across T1 reduces, the voltage across D1 remains equal to 10 V up to a duty cycle of 88 %. A higher duty cycle results in a lower voltage. At 94 % the voltage of 4.8 V proved to be just enough to cause T1 to conduct sufficiently. This value may be considered the maximum duty cycle. At this value the transistor is just about 100 % in conduction. At 230 V mains voltage, the voltage across the lamp is only 2.5 V lower, measured with a 100-W lamp. Just to be clear, note that this circuit cannot be used to control inductive loads. T1 is switched asynchronously with the mains frequency and this can cause DC current to flow.

Electronic lamps, such as the PL types, cannot be dimmed with this circuit either. These lamps use a rectifier and internally they actually operate off DC.A few remarks about the size of R3 and R4. This is a compromise between the lowest possible current consumption (when the lamp is off) and the highest possible duty cycle that is allowed. When the duty cycle is zero, the voltage across the resistors is at maximum, around 128 V with a mains voltage of 230 V. Because (depending on the actual resistor) the voltage rating of the resistor may be less than 300 V, two resistors are connected in series. The power that each resistor dissipates amounts to a maximum of 0.5 W. With an eye on the life expectancy, it would be wise to use two 1-W rated resistors here.

Assembling Technique

 

Arduino script

int ledPin = 3;
void setup(){
Serial.begin(9600);
Serial.println(“Serial conection started, waiting for instructions…\n0 = Off\n1 = 25%\n2 =               50%\n3 = 75%\n4 = 100%”);
}

 

void loop (){

if (Serial.available()) {
//read serial as a character
char ser = Serial.read();

 
//NOTE because the serial is read as “char” and not “int”, the read value must be compared to character numbers
//hence the quotes around the numbers in the case statement

switch (ser) {
case ‘0’:
analogWrite(ledPin, 0);
break;
case ‘1’:
analogWrite(ledPin, 64);
break;
case ‘2’:
analogWrite(ledPin, 128);
break;
case ‘3’:
analogWrite(ledPin, 192);
break;
case ‘4’:
analogWrite(ledPin, 255);
break;
default:
Serial.println(“Invalid entry”);

}
}
}

Download the complete project here

Make your Scooter Headlight Brighter

I have been using Honda Activa 125 scooter to commute to office – a commute of 40 km each way and on my return journey, the incandescent bulb of the headlight was useless. It probably, merely, served to tell people of my presence on the road.

I decided to switch to a halogen bulb from stock HS1 35/35W 12V bulb, and I started research for this over the internet. Then I released that I need to update the stock bulb to halogen H4 60/55W 12V bulb.When I usually invest money in buying something  I make sure the  results are worth that value. While searching, i came across this Philips CityVision Moto H4 bulb which is designed for city riders.

I asked expert opinion about changing the stock bulb to my friends and mechanic but some people said it will be useful and will work well, some said the headlight power will decrease and some said if I’m riding at low rpm the brightness will decrease. After all these comments in decided to spend 500 bucks on the bulb and give it a try. If it doesn’t work I can revert to stock settings. After all H4 bulbs can be fixed to new Activa in the stock HS1 bulb holder.No wiring or electricals has to be altered.

I bought this bulb over Amazon and went to a mechanic to change the bulb. He said the headlight performance will decrease. I told him to give it a try and he changed the bulb.Now the headlight is very bright and I’m happy with the visibility that new bulb provides.

Problem:
Activa uses AC system to power the headlight and so there is no reason that battery will drain away but headlamps get AC voltage, so it dimms and brigtens up until rpms are bit high.Some bikes use DC system to power the bulb and hence, the suggested system will drain the battery.Honda alternators doesn’t pump up the 55W bulb to full glory so at low RPM. You can probably design a circuit to switch over the power supply to DC at lower RPM’s and AC after certain RPM’s.At low RPM’s 55w bulb will not help much unless you go ahead rewind your alternator.

Solution:
This problem can be solved by changing the indicator, brake light and tail light to LED bulb which can reduce the load on the alternator.I will be doing that soon.

Expedia Virtual Card, Did it changed how Travel/Vacation Rental industry worked ??

What is Expedia Virtual Card? 

When a customer reserve a room in hotels, Expedia sent a reservation confirmation to the hotel in which they summarize customer data and the specification of the reservation. After the guests check out, the hotel had to issue an invoice to Expedia, which provided the balance, usually after 30 days.

The Expedia Virtual Card is a faster method to receive the balance of the reservation. In fact, along with the data of the customer and booking summary the details of a virtual credit card consists of a number and an expiration date are sent. After the guests check out,  the receptionist, through a common POS, provides the Virtual Debit Card and then cashing in immediately the balance of the booking as well as reported in the summary posted by Expedia.

What does the use of Virtual cards from Expedia? 

First of all it streamlines the work of who is responsible for invoicing. In fact, who does not adhere to the EVC system must issue a receipt to the customer, issue the invoice to Expedia, go to ExpediaPay, enter the invoice data and the reservation and wait about 30 days to submit the bank balance of reservations. Thanks to Virtual Card, the booking is paid in full immediately upon departure of the customer resulting in savings in human resources.

After Last minute, so even Expedia streamlines the invoicing process while it remains pegged to the Booking.com’s strength ie direct payment in  the hotel and subsequent issuance of invoice for the amount of commissions.

A single point in disfavor of the Virtual Card is that you have to pay a percentage to your lending institution. Moreover, rule valid for all credit card payments.