Monday, May 14, 2018

Simple 12V Lamp Blinker

This blinker that I'm going to show right now can be used in automotive application or any other application that is suitable. As the title suggests it is going to be a very simple diagram with minimum component count.

Component list:

1 12V Relay

1 220µF 35V

1 220Ω 1W 

12V 5-21W 


Working Principle

The circuit itself is very simple. When the power is turned on the 220µF capacitor starts to charge via the 220Ω Resistor. As soon as the voltage reaches the working voltage of the relay it turns on. When it turns on it completes another path of a very low resistance through which required amount of current passes to the Lamp to light up. But that depletes the capacitor completely and relay stops again. As the relay stops the Lamp extinguishes and the capacitor starts to charge up again and the whole process repeats.


Increasing the value of the Resistor and the capacitor will increase the time it takes to charge up the capacitor which will lower the blinking frequency.

Make sure to use a relay that can handle the amount of current required for the lamp.

Wednesday, May 2, 2018

Powering up SBC - The Right Way

As with the rise of IoT and interesting little projects single board computers are becoming more and more popular. With each iteration they are getting more powerful as well which makes it imperative to have a good quality stable power supply. You can have everything okay with your project but a bad power supply can make things go sour and that power supply can make it difficult to troubleshoot as well. If you measure, even if it is not a good quality USB power supply you might see something like 5V and that can give you the false impression that the power supply is okay. It might be okay but as soon as you load it up it might not stay stable at 5V which is required for many of this single board computers to run.

The Power Source

In the early time for SBC they didn't have much on them so 1.5A of current was more than enough even I ran my RPi 2 with 1.35A just fine, with a single USB flash storage device connected but as time goes on more and more things are added to the board itself. Now RPi has built in 5GHz Wi-Fi and Gigabit Ethernet. So that 1.35A power source is no longer suitable. Furthermore if you add mechanical storage, say a portable Hard drive, that drive alone will consume around 1A, so in that case either you have to provide around 2.5A to the board or use a powered USB Hub. The latter one is the better solution. Don't just try to run it on a 1A charger of questionable built that was lying on the floor for couple years.

The Cable

So you have a good power source yet you are having issue with it, why! Well a good quality power supply is not everything, you have to deliver that power to the device properly, so a good quality wire is also as important as the power supply itself. As not all cable will be able to carry high current without dropping too much voltage. Many of the cheap cables that are available in the market can be good up to 0.5-1A but try pulling more voltage will go down to unstable region. Cable length is also important, longer the cable is usually higher the resistance is so more voltage will be dropped across it. Also the connectors are important, a tight and secure connection is necessary for delivering stable power. If the connectors move too much the board might not run properly.

How much is enough! 

Then how much power is enough? Well depends on your project and the board itself. Refer to the product manual or website to know the recommended power for it. Add more device and add more to it. For example if a board needs 1A to run by itself and you add one portable HDD and a pair of mouse keyboard, you need to provide a total of 2.5A to make it work properly. You will be needing a cable that can deliver that much power as well. Yes I'm saying power but stating current but you should know what I'm talking about. 2.5A at 5V is almost 12.5W.

A few words on RPi

If you plan to run multiple devices from a RPi USB ports directly do keep in mind that all 4 of them will provide 1.2A total. So make sure you don't try to run a pair of portable HDD directly on them as even you plug in a 4-5A power source, they won't run properly. Again like I said above use a powered USB Hub. If you see the RED LED is getting extinguished and coming back again or on the display(if one is connected) a power icon on the top right is seen that is the indication that RPi is not getting enough power.

Thursday, April 5, 2018

Lithium Battery charger Using TP4056.

If you are looking to charge Single Cell lithium Ion/Poly and don't want to make complex circuit and fiddle with it you can simply use a Battery charging module that uses TP4056.

A few important characteristics:

1. TP4056 is a linear Lithium battery charger that can put out a maximum of 1A charge current.

2. It does have a soft start feature that reduces the inrush current.

3. Can be easily powered via USB.
4. Single Resistor to control the charge current. Programmable from 130mA to 1000mA.
5. Two status Indicator LED for easy situation understanding and troubleshooting.
6. Can be bought with Protection circuitry built in.

Let's take a look at the board:


Wiring up this board can't be any easier. Just connecting the B+ to positive terminal of the cell and B- to the negative terminal of the cell is all you need to do.

Selection of Charging Current:

It is a good rule of thumb to charge at 0.5C that means if you have 2000mAh rated cell, charge it at 1000mA rate. Although lithium cells can be safely charged to 1C if it is not too hot yet 0.5C should be a good balance between pushing the cell too much and time required to charge it.

Datasheet contains more valuable information like what is meant by the LED indicators and what should be the proper resistor for certain charge current.

That is pretty much it for the post, for datasheet and other resources visit the links below.

1. Datasheet Bank.
2. Visit My full Blog for more circuit diagrams and other interesting stuffs.

Tuesday, April 3, 2018

Why Bangladesh needs Nuclear Power Plant

  1. Bangladesh is running low in it’s Natural Gas reserve. Already good amount of Gas(LPG) has to be imported to meet the demand and with time it will only increase. The way households in Bangladesh use gas it is not going to last long. Moreover Gas Transmission Titas is corrupted to the bone, they sold huge amount of Gas to industries taking backdoor money from those industries so Bangladesh needs an alternative source of power. With Nuclear plant household can rely on Electricity to cook as excess electricity should theoretically make it cheaper. This will offload the pressure on Gas.
  2. Vehicles that run on Natural Gas can be replaced with electrical one as with cheaper and more available electricity those vehicles will be able to top themselves up without significant disturbance on the Line.
  3. Fertilizer factories will still require Natural Gas so offload the pressure on them is important. If Bangladesh runs out of Gas it will have to import those fertilizers as well.

Monday, April 2, 2018

Ceiling Fan Regulator or Incandescent Lamp Dimmer Circuit

Good Evening.
Let's look at a Ceiling Fan regulator or an Incandescent lamp dimmer circuit and see how we can make one by ourself.

Components Required:


1 500KΩ Variable
1 4.7KΩ


1 0.1µF 100V Ceramic.


1 DB3


1 MAC97A8


This circuit will be in series with the load that needs to be controlled.

Working Principle:

In terms of how this circuit works, it is pretty complex so I'm not gonna go into much details here but I will talk about those components and how they work in some other post. These components are a TRIAC and a DIAC. To explain the circuit simply what it does is change the normal sine wave that we get from main line in order to provide less power to the appliance thus dimming the lamp or slowing down the ceiling fan. However as it distorts the sine wave many appliance like LED lamps won't work with this type of Dimmer. 0.1µF capacitor is used for triggering which first charges via the Variable Resistor. Higher resistance means more time will be required to charge up the capacitor.


1. This circuit runs on 220V AC main line. To avoid electric shock do not touch any part of it during operation.
2. To modify any part of the circuit make sure to disconnect it completely from main line.


1. Datasheet bank.
2. Visit My Full Blog.