Κυριακή, 26 Απριλίου 2015

Control Your Appliances via Bluetooth

This project is the brain of the future house, you can control your home through internet from another place of the world and just an ethernet shield connected to the arduino board, you can control your home through wi-fi with another module, with this circuit I show you, you can control your appliances through bluetooth with your android phone. Based on the project of these Thai guys "http://androidcontrol.blogspot.ie/2014/06/android-bluetooth-control-8-devices.html" and the android app here: " https://play.google.com/store/apps/details?id=com.app.control", now our life can be a lot easier since we can turn on a switch which controls a lamp or the water heater from our bed! The project is based on an arduino, which depending the data it takes from the bluetooth module controls 8 digital pins-outputs which are controlling 8 relays-switches. In my occasion the specs of the relays were : 5V coil, switch 230V. Meaning that the relay could be armed with 5v and can control a load till 230V. The module I got had also 8 LEDs which show when the relay was armed, and also 8 npn transistors and 8 optocouplers which controlled the relay for better protection.

The schematic is very easy to follow and with the arduino code the Thai guys provided, this project can be made in an evening, now depending on your demands you can use it as you like. The video here is very informative and it shows how the program works, it also has 8 independent timers which can be set for different timings. Every time I pressed an output on my phone, a relay was energized and an Led was light on. If I pressed again the same output the relay was de-energized and the Led was light off. Finally I also provide 2 types of code one with active low, meaning all ouputs are off and when you press your phone they go high, and one code active-high meaning all outputs are high, and when you press your phone they go low, I suggest to use the active-low code.
Arduino Code : https://www.dropbox.com/sh/ceqntenyh8jbwy4/AABw_n1hyKHJG9HRrZmw4H44a?dl=0

Κυριακή, 19 Απριλίου 2015

Repair A Power Supply of A PC

A few days ago a friend of mine gave me a fault power supply, which he was going to through away. I tooked it from him and I repaired it. In most cases of a pc power supply the problem may be occured due to false capacitors which are the first parts to show some damage in a period of time. One big advantage if a capacitor is false it's that you can see it immediatelly (mostly!) without a special meter, because a blown capacitor looks different from a good capacitor. Precautions must be taken in case a capacitor still is charged because you might have a good zap! Measuring the voltage across their legs and discharching through a 5W - 1KΩ resistor is a good solution. Opening the case I was lucky to find quickly the two bad components. Unfortunatelly I didn't took a picture from them when they were on board but afterwards.

The capacitors where positioned in the corner left, as you can see from the pictures the difference between 2 fault capacitors and 2 good capacitors are visually easy. Pay attention to capacitance ratings and voltage ratings, The ones you change should be same capacitance and if not same voltage, then bigger. If they are bigger voltage pay attention because the size of capacitors increases too and it will need some extra effort putting it back to the board. Next step is to download a schematic with all the wires and their names (voltages) connected to the 24-pin clip or 20-pin clip. (In my ocassion 24-pin).

As we can see there is a pin named "PS_ON#"  (in most cases it's green) and this one should be connected to ground if we want to power on our supply without connecting it to a load (e.g. the pc).

Next step is to measure all the voltages according to the above schematic, so these are the values we should take from every pin. :  +3.3 Volts,   +5 Volts,   +12 Volts,    -12 Volts. Colors of cables should be different but in my occasion 3V3 was orange, 5V was red, +12V was yellow, -12V was blue and Ground was black.

If all voltage pins are the same with the schematic above, then you are set to go with a new power supply!

Δευτέρα, 6 Απριλίου 2015

Arduino Car Controlled by Bluetooth

In this article you will read about the construction of a car controlled by your android phone. It might sound a bit complicated but the hard part is the android part, thankfully Andi.co with the app "Arduino Bluetooth RC Car" has made out life easier, all we have to do is download the app and connect to the bluetooth module once we have programmed the arduino board, and make our electronic connections. Following the schematic, we'll see that we connect a 9v battery to our motor controller which is a L298N Bridge, basically it gets orders from our arduino and does all the "heavy duty work" since arduino can't provide directly enough power. My L298N board had a voltage regulator, so the Battery clips were connected to the pins "Vin" and "Ground", also I connected my battery to 'Vin" and "Ground" of arduino. In the schematic you will see the rest of the connections of the L298N which afford the connections betweens motors, and the arduino pins. Finally there is the bluetooth module which has 4 connections and they are 5V,Ground, Rx,Tx. As we know from the previous project Rx of Arduino connects to Tx of Bluetooth module and Tx of Arduino connects through a voltage divider to Rx of the Bluetooth Module. We can connect any type of resistors as long we can provide 3.3 volts to our pins. In my example I use 1K and 2K. The rule of the voltage divider is this : Vout = [Rdown / (Rdown + Rup)] x Vin. So : [2K / (2K+1K)] x 5V = 0.6666 x 5V = 3.3 Volts. Lastly one crucial reminding is : DON'T CONNECT THE BLUETOOTH WHEN YOU UPLOAD THE SKETCH TO ARDUINO, or else you will have some conflicts and you will scratch your head for hours!