I have a 42" Samsung LCD tv (with CCFL backlight)for a little over 3 years now. Recently the tv would repeatedly restart when turned on, but would eventually come on, after a number of restarts. The number of restarts were increasing every day. I realized the tv is going to fail to turn on sooner or later. I searched on the web about such problem and interestinly enough found couple of youtube videos explaining the problem and how to fix this. Apparantly, the problem happens due to two failed electrolytic capacitor used in the power supply unit of the tv. Those are two 1000uF 10v electrolytic capacitors to be exact. So I went ahead and opened up the tv last Sunday to check if my tv is suffering from the same failure. Here is the photo of the power supply unit of the tv:



This image shows the two failed capacitors, the capacitors with lifted tops.



This image shows the back side of the circuit board, where the polarity of the capacitors are marked.



This image shows the two capacitors from side and their specifications.



So I went to RadioShack to pick replacements. RadioShack had a little higher voltage rating and little lower temparature rated replacement which would work fine. RadioShack had 1000uF, 35v, 85C rated ones. The original was 1000uF 10v 105C. So I picked up two of those for $1.79 each. After removing the bad capacitors, I soldered the new ones. Then started the re-assembly of the tv. Once done, I powered up the tv and it came on without any issue, no more restarting. :-)

This photo shows the two capacitors that were replaced.

I am currently working on a 40x8 scrolling dot matrix display driver based on arduino. I need to design some custom fonts in binary format for that. I looked around the web for a tool and found some excel based tool which are not very quick and easy to use. So I came up with this javascript based 8x8 pixel font generator. Hopefully it will be useful for others too.

 

0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0

Binary code:

Just click on the segments you want to light up. Clicking two times will turn the segment off. The binary font code will be auto-generated on the right. Reset button with reset all the segment status to off.

This tool and a 80x4 matrix image code generator is available on the Tools page.

In my last post I posted a sketch that takes advantage of codes copied and modified from the Henning Karlsen GLCD library for arduino to work in the ChipKIT Uno32 board. This time I modified the library to work with ChipKIT Uno32 IDE.

Here is the updated library for download:

RGB_GLCD_CK.rar (159.96 kb)

Here is the updated library in use to display bitmap images:



Arduino sketch is here for download:

RGB_GLCD_Bitmap_CK.rar (50.89 kb)

I recently purchased a ChipKIT Uno32 designed by digilent inc., that is based on a Microchip PIC 32 bit processor. They claim it to be compatible with most arduino shields and they also released a arduino ide compatible with the chipkit boards. I purchased the board from nkc electronics and found they are selling a RGB 65K color lcd module for about $5. I ordered that as well. When I received the items I made a shield for the color lcd module. The module has solderable contact pads, therefore it is not as dificult as those nokia knock off color lcds to make contact points. I followed the circuilt nkc electronics use on their RGB Lcd shield for this display module, they sell the shile for $19.99. Here is the circuit:

 

After getting the module hooked up, I first ran the example sketch posted on the product page of nkc electronics. That was very simple and compiled fine in the ChipKIT IDE (mpIDE, multi-platform IDE), which is a modified version of official arduino IDE. Then I looked around the web for better example codes and found a interesting video demo on youtube. Then tracked the source site for the arduino library and example sketch from here. But the library does not compile in chipkit IDE. Because the library uses some macros and libraries very specifically written for avr microcontrollers. Although chipkit is compatible with arduino IDE and most shields, does not mean all the libraries will be directly compatible, due to the fact, architecture between AVR and PIC microcontrollers are different. So I wrote an arduino sketch by slightly modifying the library, which compiled fine and ran successfully on the chipkit board. Here is the video:

Here is the arduino sketch:

RGBLCD_PK.pde (18.78 kb)

Next is to modify the code to get the bitmap display to work. :-)

I found this very well written blog post on the web on how to use your microcontroller with limited I/O pins to drive large dot matrix led displays. The atricle explains how to use 74HC595 shift registers to scan multiple dot matrix display modules's columns and a CD4017 decoded counter to scan the rows. All together you will need 3 I/O pins for the shift register and only 2 I/O pin to drive the decoded counter.

Here is the link: http://embedded-lab.com/blog/?p=2661

I have used 74HC595, CD4017, ULN2003 chips to drive dot matrix displays already using arduino, but that was static/non-scrolling. This blog post gave me better understanding on how to do the scrolling.

Last Saturday was the warmest day of the year here so far. So we went to the park to do a outdoor test of my Qaudcopter. I had a sony bloggie video camera on board but unfortunately the camera lens was tilted downwards too much, so all it recorded was the ground with occasional brief horizon views during pitch/roll maneuver. However, the second camera did capture the flight quite well. Here is a short video of the flight..



The quadcopter controller is running on a homemade arduino board with Atmega328 (running at 16HMz) and the homemade sensor board mentioned in my last post. The sensor board has ITG3200 gyro & BMA180 accelerometer for stable flight mode and BMP085 barometric pressure sensors for altitute hold. I am using Hextronix 24 gram brushless motors and Super Simple 10A ESCs from hobbyking and a 4000mAh 2 cell lipo battery. The frame is made from round aluminium tubes and I am using a align t-rex 450 helicopter landing skids.

Here is a short video from the onboard camera:

Figure: 9 DOF Sensor board right after etching

When I started to gather interest in making a quad copter inspired from open source projects around the world, there was one problem. That is getting the gyro, accelorometer, magnetometer and barometric pressure sensors. All these sesnors are used to keep the quad copter stable in flight and for purposes like altitude hold, heading hold etc. The sensors very small package smd devices, are a bit hard to work with when it comes to DIY. Sparkfun electronics sells the sensors on breakout board, but those seem a bit over priced for me. For example, the ITG3200 gyro break out board was priced at $49.99 when the sensor chip can be purchased at $10 a piece. So I decied to give it a try after reading some tips about DIY smt/smd soldering on the web. I tried hot pan soldering couple of times but it partially burnt the pcb in process making it look very ugly but the sensors worked. Then I moved to toaster oven convection heat soldering and it seems to work much better. I got a cheap convection toaster oven for $29 on last black friday and I am quite happy with it. So here is my latest attempt of smt soldering, which involves making a all-in-one sensor board for my quad copter:

Figure: 9 DOF Sensor board after soldering

Although this process does not always go perfectly fine, I am happy to say that all my sensors worked perfectly fine. Here is it in action within MultiWii configuration tool:

Figure: 9 DOF IMU & Baro sensor reading in MultiWii config

I know my board does not look as good as the manufactured boards with silkscreen and things but it works and I am happy with it as it saves me money to buy more gadgets to play with.  The total cost to make the board included $10 for ITG3200, $8 for BMA180, $8 for BMP085, $3 for HMC5883, the I2C voltage level converter plus other passive parts cost were about $10, which brings the total to roughtly around $40. I spent around $10 for shipping for all the components. Still it is much cheaper then buying these sensors as breakout boards from Sparkfun or buying it from ebay for $99 which does not include the 3.3v regulator and I2C level converter.

This board has built-in 3.3v regulator and I2C level converter to use this board directly with a 5v powered arduino or any microcontroller board.

Here the schematic for anyone out there to give this a try, the schematic is based partially on Sparkfun breakout boards schematics, data sheets, and partially on the Free IMU project.

 

Figure: Second version of the board with corrected circuit for HMC5883L magnetic sensor and smaller board size.

I needed to make a little modification for the HMC5883L magnetic sensor, which has a little bit different application circuit than HMC5843 and HMC5883 version of this sensor.

Here is a short video of the sensor showing the output in MultWii config:

I have been working for a while on building RC quad copters. First I built a medium sized one following the Aeroquad hardware and software. But I was not very happy with the performance. Then I decided to build a small one which can be safely flown inside home for debugging and flight practice.  I tried aeroquad software on it first, but didn't get good result. Then, I was follwing the MultiWii threads and found they are expanding their code to support more hardware and that included Aeroquad hardwares as well. So I downloaded the latest MultiWii code and modified it to work with Aeroquad hardware (ITG3200 gyro, BMA180 accelerometer etc.). Here is how my mini quad prototype looks:

And here is short video of it in action:

How about a robotic bird that looks and flies like a real bird?

More information about this project can be found at: http://www.festo.com/cms/en_corp/11369.htm

I recently purchased the HC-05 RS232 serial bluetooth module from eBay. These modules sells from $10 to $20 including shipping. My plan was to use it as a economic wireless communication tool between PC and the Arduino board. The module has built-in Serial<-->Bluetooth protocol converter. Therefore it can be connected directly to Arduino serial pins without any ttl level translator chip and with a few external components. One thing to note though, the seller I purchased the module from on ebay had the wrong schematic posted on the listing which was meant for a older version of this module. So depending on which version you have, you will have slightly different pin connection for the AT command enable pin and led indicator pins. The major difference between the two version of the module is, the newer version works in both master and slave mode depending on how you set it up via AT commands and improved firmware. The specification of this module is as follows:

● Bluetooth protocol:  Bluetooth Specification v2.0+EDR
● Frequency:  2.4GHz ISM band
● Modulation:  GFSK(Gaussian Frequency Shift Keying)
● Emission power:  ≤4dBm, Class 2
● Sensitivity:  ≤-84dBm at 0.1% BER
● Speed: Asynchronous:  2.1Mbps(Max) / 160 kbps, Synchronous: 1Mbps/1Mbps
● Security:  Authentication and encryption
● Profiles:  Bluetooth serial port
 
Power supply: +3.3VDC 50mA
Working temperature: -20 ~ +75 Centigrade
Dimension: 26.9mm x 13mm x 2.2 mm

Here are the data sheet, example schematic for this module:

BC4_Bluetooth Module Datasheet.zip (1.12 mb)

The schematic I used to connect to arduino is as follows:

This can be used as a cheap way to talk to your Arduino wirelessly and debug your quad copter over serial port without using the relatively expensive XBee modules, even though you will not get as much range as the XBees.

Here is my version of the break out board.

Figure: Front side of the break out board.

Figure: Back side of the break out board.

Testing the module with MultiWii quad and configuration tool: