Salt Water Etching [Electrolytic etching of PCB]

This is an alternative method for the etching of PCB's .Its a lot different from the other methods where we use ferric chloride or else hydrogen peroxide.

In this method we use the PCB to be etched with salt water solution and also another electrode made of copper for the etching.

The steps for the etching is as follows:

• Prepare a saturated salt solution with water in a plastic or glass container.[ Its just adding salt to water to such an extent that the salt stops dissolving in the water.
• Prepare a power supply for the process. I would recommend a 12V DC supply or else a variable power supply such that the voltage be controllable. Also add a 750mA fuse just for protection.
• Connect the negative of the supply to an copper electrode and dip it in the salt water solution. In the below photos I have used another copper clad laminate as an electrode which is feasible.
• Connect the positive of the supply to the PCB to be etched. Make sure the terminal is connected to a path which goes all round the PCB such as a ground. I have soldered the power terminal to the board. Now dip this solution into the salt water. Make sure that both these connectors are far away from each others. The PCB is to be made ready after the printing of the resist and cleaning the board.
• Turn on the power supply and you can see small bubbles from the electrodes. Keep checking in between to notice the status of it. Once the etching is done , clean the board off the resist, drill and use it.

Have attached the pics and their description below

My test board, i just signed on it using a marker. Also the supply terminal is soldered.

This is just after the connection of the terminals of the power supply.

We can see the bubbles rising from the electrodes.

I used a 12V battery for the process, pic of the setup

After a while of the process, the solution turns to bluish green colour with smell of chlorine

Water Level Sensor

As said , this is a water level sensor which contains the connection to a relay which operates a solenoid valve connected to the relay.
The list of components are:

1. Green connectors -2pcs
2. Molex 2 pin connector -1pc
3. 1N4007-1pc
4. 2N3904- 2pc
5. Resistors: 10k,1k
6. Led - 5mm - 1pc
7. 10k Pot
8. Solenoid valve to suit the need -1 pc
9. Relay: with actuation voltage same as that of the solenoid
10. Power supply to the rated voltage of relay and solenoid, 1A

The schematic and layout of it are attached as follows:

In order to make it work, the power supply is to be given to the PCB. From the 2 pin molex connector 2 wires to be drawn and left to the maximum necessary water level. The pot is to be adjusted such that the LEd glows with full power.

The PCB works as follows, water is a conductor of current to some extent depending on the impurity in it. The transistor in the PCB is given the base current from the power of the supply and passes through the water layer and then to the ground from the pot. The pot is used to adjust the triggering level of the relay. If necessary a solenoid can be used or else some kind of necessary actuator which is necessary by the user. The jp3 is the output terminals of the PCB.

The PCB layout in pdf format is given below:

water level sensor

Thank you all for waiting and sorry for the delay. Will keep updating soon from now.

Water Level Sensor

Made a water level sensor for water coolers. 

Also simultaneously there is a water level monitoring system for most of the water tanks with the level display.

The water level monitor and control system consists of a couple of transistors, power supply , relay and solenoid system.

A solenoid is a hydraulic and pneumatic switch. Whenever the level of the water goes down below a level then the solenoid is shut off. Whenever the water level is below then the solenoid opens up to fill in the water to the desired value.

Sorry was busy with the college work. Gonna put up the complete circuit and photos by this thursday.

Thank you 

Serial port ISP programmer

 Beginners in electronics , especially into microcontrollers normally lack a programmer for embedding the program into the controller. There is always an option go and buy one but considering the cost of making one and the purchase of  a new one, making one is easier and cheaper. This is an AVR programmer. The cost incurred to make one is about 50Rs in total cause it only involves a few resistors, a transistor ,7805 and a serial port connector.

I have made and tested this programmer circuit. The schematic is connected as shown below.

The layout is given below.

serial port ISP

In order to interface this to the microcontroller, The six pins in the layout to be connected to the six pins of the microcontroller. The pinout of the layout from the top to bottom is as MOSI, MISO , SCK, ~RESET, Vcc and Gnd. The software to be used is called ponyprog , you can download it from here for free http://www.lancos.com/prog.html.

We can also make USB programmer at home but it requires a controller in its design and for programming that controller we need a programmer.

Portable Cell Charger

This is a portable cell charger that I'm using when on short trips. Its a very simple circuit containing a USB female port, a 7805 and an LED. I use a 9V portable battery for charging my cell with the help of a USB charger.

The PCB , schema and layout are given as always.

Cell charger by

Light sensor

The light sensor senses the solar output and keeps the connected load turned off until a certain brightness of the light which can be controlled using a pot. When the brightness goes down the required value then the load is turned on automatically. The circuit uses a LDR [Light dependent resistor] and a transistor 2N3904 to detect the light and give output from the relay.

List of components:

1. Resistor: 470ohm / 1watt
2. Capacitors : 0.68uF and 47uF
3. Diodes: 1N4007
4. Zener diode: 15V, 1/2W
5. Transistor: 2N3904
6. Pot :10k , pcb mountable
7. Relay: any 5V single pole relay
8. Green connectors : 2nos [ 1for input and the other for output]
9. LDR [ light dependent resistor]

The pcb layout

Light Sensor by

The PCB operates on very simple basis, the transistor turns the relay on and off. The LDR when exposed to light actuates the relay which in turn opens the light circuit, when there is no light to LDR then the relay is deactivated which turns on the light.

The same PCB can be used for some other applications such as automatic door bell, unmanned railway crossings and many more. Make sure to connect the line and neutral in proper fashion as shown in the image above.

Note: Make an alternate wiring for the light such that in case of necessity we get to turn on the light even on day time and if possible to turn it off too.

Next to be updated

The next update would be of light sensor for most home applications.
The detector would be placed at the a proper place where the sun would be in the line of sight to detect sunlight. When in short of the sunlight , it would switch on a tubelight or else a bulb to which it is connected.

TO be UpDated in this week.