Hello guys, hope we have all been fine and hope we enjoyed the last post.
Today we will be talking about how to build a mini power bank using a voltage regulator ICS.
And later we see how to build a standard power bank with this post video than you as you follow
Power banks
They are portable devices popularly used to charge phone. But trust me they can do a lot more than just charge phone.
Methods used in building power banks
There are different topology one could use in building a power bank, but in a standard power bank circuit they use inductor capacitor network to boost the voltage from 3.7volts to about 5volts at the desired current and in some other circuitary they use DC to DC boost converter IC called voltage boosters e.g ADP1612 and ADP1613 e.t.c which is among one of the most popular voltage boosting ICS,
But on this post we will be using a different topology then on the next post we use a boost converter circuitary.
We will be making use of voltage regulators in building this power banks which are the topologies used in cheap lamps with USB port and radios with USB port.and we need to know the qualities a power bank has before building one
Qualities of a powerbank
Power bank carry a voltage ranging from 4.9volts to about 5.1volts which is still OK for the phone, but they vary in how much current they can deliver and how much time the batteries could last.
Methods used here
1. Using zener diode
2. Using 7805ic voltage regulator
3. Using lm317 voltage regulator ICS.
Using zener diode.
These are one of the simplest method to build a power bank in that they are cheap readily available and less stressful and less technical to build.and the battery voltage needs to be at a higher potential than the zener diode to produce 5.1volts, therefore 2 piece of 3.75volts battery in series will give us 7.5volts which is capable now of giving us 5.1volts output on our zener.
We make use of a 5.1 volts zener, and the reason is that any voltage we pass through it, it will always give us 5.1 volts bit then we need to consider the current we are drawing from the zener and with this we don't get to be able to deliver much power to our phone, like tablets and other sophisticated phones so that takes us to method 2.
This is the circuitary please pardon my diagram, the batteries are connected in series to get higher voltage of 7.5volts then the zener diode is acting a voltage level converter for our phone.
Using 7805ic
This is a voltage regulator IC and comes in different forms varying from 7805 capable of delivering 500ma to ones capable of delivering up to 2amps, but the most common types deliver 1amp which is lm7805cv and this IC also need 2 volts higher than itself to perform well but can only see deliver 1amp and if our phone is powerful it forces the 7805 to want to output more and by so doing the 7805 over heats and enter thermal shutdown mode, but it has an advantage in that it will still charge common sophisticated phones without stress.
This so the circuitary used to convert the already boosted voltage from 7.5volts back to 5volts needed by our phones and the diagram below.
Using lm317
This is better voltage regulator IC in that it is capable of delivering as high as 1.5 amps at a wide varying voltage up to 35volts, they are much better than 7805 in terms of power handling and heating up, I strongly recommend this circuit for power hungry phones like tablet phone and more sophisticated phones. But you will have to use your screw driver to vary the voltage to 5volts your self. And it also needs a battery voltage which is at 2volts higher potential than the expected output voltage to perform well, therefore 2pairs of 3.75volts battery will do the job and the 7.5volts is later regulated down to 5volts at about 1.5amps maximum which is very OK for our phones
With this voltage regulator IC you have to tune the variable resistor to get the desired voltage and please measure with a multimeter before interfacing with phone.
Thank you very much for following us. This really works I advice you try it out and any challenge or issues please feel free to ask on comment below and I will be sure to get back to you as soon as possible. on our next post we will be talking about building powerbanks without needing to first step the voltage up then regulating it back to 5volts this time we will be boosting the voltage to 5v directly from 3.75volts which is used in standard power banks.
stay cool, keep peace with everyone, be right back and thanks again
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