Electronics for fun

Homemade Pickit2 lite

2012-10-30T09:02:00.000-07:00

You may have programmed PIC using microchip pickit-2,It is a easiest way of programming microchip programmable ICs.I will show you how to make your own pickit 2 in a easiest way.Following site helped me to create the pickit 2 lite.Here is the link to the site-http://dlmkerode.tripod.com/PICKIT2_1.htm

I will show you,how I made it in home step by step.

1. Preparing the PCB

At first time,I made pickit on a vero board.I realized that it can use to programme PIC10F, PIC12F5xx, PIC16F5xx, PIC12F6xx, PIC16F, PIC18F, PIC24.Then I moved to create pickit2 on a PCB.

#schematic of the pickit2 lite is as follows

Using Proteus,Eagle cad or any cad software you can make the PCB layout of the schematic.I used following technique to get the pcb layout to copper plated plate.

http://www.riccibitti.com/pcb/pcb.htm

#pcb layout of the pickit2

2.Inserting components and soldering

There is an inductor on the circuit which is hard to find in local market .I ordered them from ebay.It took only a week to receive me.

http://www.ebay.com/itm/Inductor-680uH-680-uH-DIP-4-x-10mm-10-40-pcs-/250435161934?pt=LH_DefaultDomain_0&hash=item3a4f194f4e

If you cant find an inductor in local market,don't worry there is an alternative in your old phone charger,radio or in DVD player.Any inductor which having an inductance of more than 330uh, can be used to replace the 680uh indutor in the above schematic.

Use a 28 pin IC base to mount the pic 18F256 to the circuit.Never solder it directly to the circuit board.Heat generated from by the soldering iron can damage the IC. Another important thing is,data cable should not be more than 1m.(sometimes may work).Because I haven't inserted the ferrite bead which is used to suppress high frequency noise in electronic circuits.

3.Programming the PIC

You can download the hex file here.To programme the PIC you need to have a another programmer.If it is difficult to find a programmer there is an alternative for that.ART 2003 programmer is easy to built and use.Click here for more info.

IR sensor panel for line following robot

2012-08-27T09:20:00.000-07:00

If you are a beginner for robotics this blog will help you to get some knowledge about robotics.Major part of a line following robot is sensor panel.You can make line following sensor panel using IR,LDR,photo transistors etc.

I will show you how to make a good sensor panel using IR sensors.

Specifications

Operating voltage: 4-5.0 V
Output format: digital I/O compatible
Optimal sensing distance: 4 mm
Maximum sensing distance: 20 mm

You can buy IR sensors(which having both transmitter and the receiver).A single IR sensor will cost about $1.

Now you have to choose whether your robot must follow the line smooth or not.If you need to go smooth,then you have to put more sensors on the sensor array.greater the number of sensors will greater the line following.

I think if you have any theoretical knowledge about IR rays,it will help you to improve the performances of your robot.
go to this link http://en.wikipedia.org/wiki/Passive_infrared_sensor.

OK,If you are beginner and you know only a little about microcontrollers I will tell you some thing about microcontrolers.Robot will find the way according to the signals from the sensor panel.There are many algorithms(such as PID) we can use to drive the robot on the line if sensor panel works properly.

Microcontroller can understand only logic 1 & 0.microcontroller port voltage for logic high is 2.4V-5V(Voh) and for logic low is 0V-0.45V(Vol).White surfaces will reflect the IR light while black surfaces absorb.Using this theory we can tell the path to robot.Sensor panel produces about 4v to 5v when IR sensor is on white surface and 0V when it is on dark surface.

Here I've used LM324 to amplify the signal from the IR sensor. Without op amp we cannot produce enough voltage to give logic high to pic,because the voltage different between when sensor is on white surface and black surface is not more than 0.7V.Basically op amp is used to convert analogue signal to digital.

Above is a image of a part of the sensor panel.I created it using Proteus software.

By changing the RV1 value sensor panel can be tuned.When there is more sunlight,sensor panel tends to give wrong signals.To avoid that, it is better to cover the sensor panel.

Motor controller driver circuit using L298

2012-08-26T10:07:00.000-07:00

I made a DC motor controller circuit using L298 to control a single motor.You may already know that L298 can be use to control two motors.Yes you are right,but maximum out put current of the IC is 2A when we use it to control two motors.But if your motor's stall current is more than 2A,it is good to having a motor controller which can produce more than2A current to get the maximum use of motors.Specially when you are designing robots you need high torque motors.So you need high current motor controllers.

Take a look at l298 data sheet page 7 figure 7.You will see a solution for drive a motor which having stall current more than 2A. But you must take care to parallel channel 1 with channel 4 and channel 2 with channel 3.

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My design is quite simple.It is easy to understand by looking at the schematic.I made the PCB using proteus software.

Here D1,D,2,D3 and D4 are shottky or fast recovery diodes used to protect transistors from surges.Use a set of 1N5819 (or alternative 1N5818) schottky barrier diodes.You can drive up to 30v DC motors.The maximum current is3.5A.It is wise to mount the diode bridge o the motor when l298 and motor is not close each other(if space between them about 1m).

In my own experience I'd like to say you that don't ignore to insert 100nf non inductive capacitor.Though you didn't insert capacitors to you design it seems to be work properly,but microcontroller is going to be reset every 3 or 4 seconds.Before e I posted my design without having capacitors.Corrected design is now uploaded.

I'm still learning on l298 motor driver and I will update my blog up to my knowledge.

Making a 555 LED Cube without led driver

2012-08-11T23:17:00.001-07:00

All you want to know is how to make a led cube.OK lets DO it.

Parts list

To make circuit

PIC18F877A
LED(any colour) -125
330R -10
Vero board -1
Circuit wire
20Mhz crystal -1
22pf -2
7805 -1
10uf -1
1uf -1

To make the enclouser

Perspex sheets.
Black coloured formica sheets.
Super glue.

Making the LED matrix

First you have to place led bulbs in a proper way to solder them.To place leds in equal distance I made a soldering jig using thin plastic sheets.You can make it also using wood.
Then you have to solder leds layer by layer.You must ensure that all the leds are working properly before soldering.
You must bend each led lead as follows in order to solder easily.
After soldering all five layers you have to mount them one by one.First layer should be mounted on a pcb as shown below.

You can easily make the bottom pcb by following link
http://www.dutchforce.com/~eforum/index.php?showtopic=13974

All the layers should solder one upon one.

Number the cathods of leds

I used a floppy interface cable to connect the led cathods with the circuit.

Anode pin of each layer(five anode pins) should be connected to the floppy interface cable.

The most important thing you must know is you have to ensure all the leds are working properly.It is hard to replace leds after soldering.

Making the brain

I make the circuit on a vero board.I'll give you the proteus schematic of my circuit.If you like you can make your own pcb.
schematic

You need no any led driver to implement this led cube.I made my cube without any led driver because I couldn't found any led driver in local market.But programing this cube is more complex.I programmed the pic using microc pro v3.6.

Here is my code.I think it is hard to understand what I have done.But you can start to program it by simple program.Then you can go through difficult ones.

********************************************************************************

You can download it in here
ledcube code