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.