Hello guys thisis another episode of electronics for the dumbest dummy. And in this episode we will be talking strictly about how to build a phone charger using a 7805ic based technology.
PHONE CHARGER
On this page we will only be talking about using transformers along side with an IC named 7805 IC to build a phone charger. Note our phone needs only 5volts for them to charge effectively at a current to charge as fast as we want but at the detriment of our phone batteries if there is too much current.7805 IC
This is a voltage regulator IC that takes in an input between 0 and 36volts and then delivers a stable output of 5volts. And has a maximum power dissipation of 15watts. Meaning you can only drop down 15watts of your power on the 7805 IC after drawing your needed power.and mostly have maximum output current or drawable current at 1ampere.and it needs at least 7volts to perform in a stable manner. To know more about how this IC works please check the datasheet thank you.
Calculation for power dissipation
P=I*vAssuming a voltage of 10 is brought in at 2ampere of current and 5volts as our 7805 output. The power dissipation will be
P in - pout.
10*2=20
Therefore input power equals 20watts.
Output power equals
5*1=5.......this equals 5watts of power I.e 5 volts at 1 amp
Therefore power dissipation equals
Voltage........10-5=5........5volts
Current.........2-1=1...........1amp
Therefore power dissipated equals 5*1= 5 watts. Power dissipated therefore equals 5watts. Still OK for the 7805 IC......that is the concept of power dissipation. And it is done in other to protect the IC from over heating due to too much wasted power. Sometimes!es if the heat is too much we might need to cool down using a heat sink and a fan or just heat sink as the case maybe.
Circuit diagram for building a phone charger and how it works.
UNDERSTANSTANDING THE CIRCUIT DIAGRAM.
This circuit diagram might be a bit hard for engineers to understand but here a quick explanation to understand the circuit. The first component is a transformer , and those lines passing the components from one place to another is a representation of wire. Then the rest a just circuit representation of a component. But it is listed below according to the way they are used in the circuit.and this circuit should first be bread boarded in case you make a mistake. Then later it can be transferred to a board known as vero board. The diagrams are shown below.
To learn how to use a bread board use the link below
https://learn.sparkfun.com/tutorials/how-to-use-a-breadboard
Breadboard
Vero board
Down view
Connection on bread board
Note the diode used in this connection is bridge wave rectifier diode
Sorry about my circuit diagram in case you don't understand very well contact blogger .
This diagram shows how a standard phone charger is build using a 7805ic voltage regulator based technology. Notice the four components used after the transformers, they are called DIODES they are the ones doing the job of converting the alternating power to direct power. I.e making the voltage and current stable in other to be useful to our phone battery. The next one after the diodes is a component called CAPACITOR it is used to filter the diodes output in other to reduce electrical noise and make the voltage smother. The next is the 7805 ic used to regulate the voltage to 5 volts. next is a resistor and led network in series to each other, The led is used as an indicator to show the transformer has been power and ready to deliver output, the the resistor is used to limit the voltage and current getting to the led. Next is a capacitor again to further filter and then a diode again to prevent discharge from the phones battery to the charger when power is off. And lastly the USB port connected to bring output.
PICTURES OF COMPONENT USED
Thankyou very much I hope this post has helped you for more about the ICS used read the data sheet and read about how diodes work. Any comment, question or problem, do well to post it have a nice time.
Transformer
Rectifying diodes.
Capacitor.
This capacitor is a 16v 2200uf capacitor. 15 volts because we need a voltage higher than the incoming voltage from transformer of 12volts
resistors. A 1k resistor is used here
Led.
Thanks a lot I hope this little post has helped you on how to build a phone charger in case you are having any problem please don't hesitate to contact blogger . and this practical should be done under a qualified engineer supervision for safety purpose
Thanks alot
2 comments:
There are many errors in this blog post, and some may result in burns to skin or the breadboard.
The general circuit design is okay, but needs modifications:
1) You need to use a heatsink with the 7805 if the power it has to dissipate is more than 1.5W, because at higher power (at room temperature of 25C) the internal die temperature will exceed the maximum rated operating temperature of 125C. At this operating point the 7805 will be too hot to touch, and it may begin to enter thermal shutdown: the output voltage will drop significantly (possibly near 0V), and the circuit will not operate reliably.
In fact, the transformer and rectifier circuit will generate at least 15V (and probably closer to 20V), so the maximum current allowable without a heatsink may be as low as 100mA.
2) The 15V bulk filtering capacitor's operating voltage is under-rated. The general rule is to use a capacitor rated at least 125% (but no greater than 200%) of maximum terminal voltage. For a 12V output transformer, the rectified voltage will be about 15V, so the capacitor should be rated between 19V and 30V.
3) In addition, the diode at the output will lower the output voltage to about 4.4V. This is probably okay for most phones, but it may be a bit too low for some phones. If you feel a diode is really necessary, use a Schottky device (which will bring the output up to around 4.7V to 4.8V.
4) Finally, with a 1k resistor, LED current will only be on the order of a few mA. This is okay for many LEDs, but it may be necessary to lower the resistor value to 150 ohms to get desired brightness.
Sorry man although I reason with what you say but the post is correct and 7805cv can deliver 5volt at 1amp moreover 7805 can dissipate power of 15watts and we have not even dissipated up to that. And the transformer am using is a 12volt transformer coupled with the diode is a rectifying diode to prevent feed back from phone battery and I realize there will be a drop down of 0.6volts but its still OK to charge a phone and most times the drop down is not even up to that sir. More over when you calculate very well you will realize that you will destroy the led if you use lower than 470ohms resistor. So am sorry the post is very correct sir. And I clearly explain in the post that you should always use a capacitor with voltage higher than expected voltage which was what I used in the circuit.
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