PAL Composite video timing

India moved to DVB T2 in 2015. I always wanted to make a system which can project images on to the biggest screen i can get my hands on. So here are details.

PAL = Phase Alternate Line

total of 625 lines

Field one + Field two  = 625 lines

each field line consist of

[ vertical sync ] [ horizontal sync + active video ]x n

each scan line if of 64 micro second. (strict constraints don’t play with margins)

each 64 micrsecond line starts with

[Horizontal Sync = 4.7 us] [ color burst = 8us] [active data] [4 us of black level] = 64 us

This scan is done from the composite line of sony playstation 2. So i am taking this as a reference.

help is taken from here

Additional notes here

ESP8266 voltage spikes on power rail

I used esp8266 for broadcasting message to my website. But to operate this chip smoothly one needs to redesign its power supply.

There are voltage spikes of around 320 mV

esp8266 voltage spikes on power rail
esp8266 voltage spikes on power rail

at normal operation the chip uses around 70 mA or current. and when broadcasting something over WiFi current  can rise to about 170mA( according to its datasheet).

This all is not the problem. Because everything works.

Problem is the voltage drop accross the lm317t.

Input voltage = 12v

output voltage = 3.3v

voltage difference = 12v – 3.3v = 8.7v

load current = 105 ma

power dissipating = 8.7V x 0.105A = 0.9135W

That’s a lot of power which is being thermal dissipated.

I used a very tiny heat sink. Also the heat sink is attached by a drop of fevicol instead of thermal paste (cheap solution)

My Suggestion:
use a 5V input at lm317t

volatge difference = 5v – 3.3v = 1.7v

power dissipation = 1.7 x 0.105 = 0.178 W

 

Internet of thing Digital Thermometer DS18B20

I purchased this ic a long time ago. Never had any chance of using it. But now the this small itsy bitsy integrated circuit is sending data on the internet.

You can check the link at http://abhaykant.com/mtb

It is connected on a custom gateway device.

The ds18b20 can take power in two ways. The circuit that i made is using the parasite power.


This time i used clear nail pail paint over the copper trace.

ds182b20 interface schematic
ds182b20 interface schematic

printed circuit board is designed in KiCad open source EDA tool.

 

UPDATE : 14 September 2018

Using nail paint as a substitute for PCB lacquer is a cheap solution. It should be avoided when making a rugged PCB. If their is a lot a mechanical vibrations and stress, then the nail paint will chip away leading to oxidation.

7805 based power supply with Voltage and current protection

7805 linear voltage regulator is an inexpensive solution. But the ic doesnt include any form of protection. So, the voltage and current protection should be externally added.

There is high chance of reversing the polarity if you dont keep which wire is what. I did the same mistake and blown the aluminium electrolytic capacitors with 7805 ic.

Below is the revised circuit from 5V voltage regulator using 7805 | Complete Process.

schematic of 7805 based power supply with Voltage and current protection
schematic of 7805 based power supply with Voltage and current protection

3.3 volt receiver signal level Interface board for esp8266-01

In my previous attempt at designing this board here. It was good. But to make the pcb smaller. I redesigned the pcb, i shifted some component here and there.

This PCB contains a 3.3v level shifter at the receiver pin.

Here are the schematics and pcb layout.

esp8266-01 interface schematics
esp8266-01 interface schematics
drill layout top esp interface
drill layout top esp interface
top silk layer esp interface
top silk layer esp interface
bottom trace esp interface
bottom trace esp interface
Top View of esp8266  interface board
Top View of esp8266 interface board
PCB bottom copper traces and pads
PCB bottom copper traces and pads

Etching time : 1 hour and 20 minutes

That’s very long time but the solution is used up. as this is a small board i don’t want to dip the board in new solution. Also i let the PCB sit for a while , and by doing this the etching is uniform and the i also found out that the traces are much sharper than before. So it is a good idea to let it sit for around 30 minutes before you shake the container. As i am doing this manually, so that is why it is a slow process.

 

Atmega32 Development Board

This development is very basic. It provides the GPIO in the form of header. As i will be using this board for rapid development and learning different coding practices.

I designed this board in KiCad – a open source l tool. From schematics and PCB layout is designed in this software suite.

Here are the schematics and PCB layout.

As i don’t have a laser printer i used the free hand sketching of traces. It is a very long and tedious process. After tracing with permanent marker and letting it dry it for few minutes. I etched this PCB in ferric chloride solution. I use very diluted solution, few grams of ferric chloride in around 200 ml water.

atmega32 dev board schematic
atmega32 dev board schematic
atmega32 dev board pcb layout
atmega32 dev board pcb layout
Drill Holes Marking
Drill Holes Marking
Copper Mask
Copper Mask

Total Etching time is around 40 minutes, After the board has been etched it needs to be cleaned thoroughly. I used utensil cleaning powder for that. And rinsed the board under water. And then let it air dry for few minutes.

Component Placement on PCB
Component Placement on PCB
Component Soldering
Component Soldering
Marking the Components on top layer
Marking the Components on top layer

The development is created. But there are few issues that came while testing the board. When i tested the board the chip does not responds. While checking for shorts or no connection on the PCB. I found that capacitor is not blocking the alternating signal. rather it is showing a short. So i had to change the 22pf capacitor with a new one and the board now works perfectly fine.

 

5V voltage regulator using 7805 | Complete Process

While making circuit a power source is the essential component. Power source can be made by different circuit. Here i used the most popular integrated circuit 7805. Which is a 5v voltage regulator.

Schematic

I made this schematic in KiCAD software.

PCB layout in Kicad pcbnew
3d rendering of pcb
3d rendering of pcb

After this i made some print out. Drilled a few holes. As i do not have a laser printer i am unable to make a photoresist mask. So i use old school permanent marker for masking wire trace.

7805 PCB in ferric chloride solution
7805 PCB in ferric chloride solution
7805 pcb final output
7805 pcb final output
Component Placement on board
Component Placement on board
Solder Component
Solder Component

It is not the best job of solder that i have done. But it is not worst i did and definitely not the best.

Nail Paint as Solder Mask
Nail Paint as Solder Mask

I did not have paint or the PCB lacquer. But in my home i found this used nail paint. It barely works.

Testing of PCB
Testing of PCB

Final output.

 

LDR Based Camera

Schematic of LDR based Camera
3d Rendering of the pcb’s

Scan the LDR reading with the help of atmega32 adc pins. Send the captured data to a computer using ftdi, bluetooth ,wifi or zigbee. Run any free math processing tool and make a image. Increasing the Number of ldr increases the resolution of the image.