The room thermometer and Bluetooth speaker are two, standalone DIY projects we have currently
built and we will be building more in the coming videos. Powering all these projects
is going to an issue and in this video, we will learn how to build a very simple USB
power hub to power your DIY projects.
When designing a power related project, there are two main things you need to worry about
– the voltage and the current. Since this is going to be a USB power hub, the voltage
will be 5V and the current should at least be in the 2-3A range so that it can safely
provide power to multiple devices at the same time. I would like to make the input voltage
a little flexible so that we can power it through different sources, depending on what’s
available. I have a spare 12V, 5A power supply that I will be using to power this.
In order to convert this 12V input to 5 volts, we need a voltage regulator and the first
one you might think off is this 7805 that is easy to use and very compact. However,
it is a linear regulator and like all linear regulators, it is inefficient. At a very basic
level here’s how they work. They have a sense network that can determine the input
voltage and they then drop the excess voltage by using something called a pass element and
this generates heat. The amount of heat generated depends on the output voltage as well as current
being drawn.
Let’s take our example here. If we supply the 7805 with a 12V input, it will provide
a 5V output. If we do not draw any current from the output then they will be virtually
no heat generated. If we draw current of around 100mA, then there will be some heat generated
and this will be noticeable after some time. Also, if we increase the current drawn to
about 500mA then there will be much higher heat generated. You would most likely have
to use a heatsink to avoid damaging the voltage regulator. This means that for a constant
input voltage, the heat generated will increase as the current drawn increases.
Conversely, if we draw the same 100mA but supplying an input voltage of 24V, then the
heat generated will be much higher, as the voltage regulator has to drop the excess voltage.
Thus, when constant current is being drawn, the heat generated will increase as the input
voltage increases. The efficiency of these voltage regulators is around 50% at best and
for that reason, we wouldn’t be using one here as we would like the power supply to
handle various input voltages and supply high current without having to worry too much about
heat.
A switch mode power supply is another type of power supply that can be used to either
convert a low voltage input to a high voltage output or to convert a high voltage input
to a low voltage output. If the output voltage is lower than the input, then it is called
a step-down or buck converter. If the output voltage is higher than the input, then it
is called a step-up or boost converter. Switching voltage regulators are slightly more complicated
compared to the linear voltage regulators but the advantage is that their efficiency
is generally around the 90% mark or more, which means that they do not generate as much
heat and can be safely used when higher current outputs are needed. At a very basic level,
switch mode regulators tend to move small chunks of energy from the input to the output.
They do this by using a switching controller and a storage element, which is usually an
inductor.
Switch mode power supplies are used in a lot of household electronics but thankfully there
are various modules available for hobby use as well. We will be using the LM2596 voltage
regulator module that is commonly available. It can safely handle a maximum input voltage
of around 40V and it can supply an output current of about 3A which is more than what
we need. This also means that you can use pretty much any power adaptor that you may
have as long as the voltage is about 9V or higher. The modules also have an adjustable
trimpot so that you can vary the output voltage which is perfect.
Here’s what you will need for this build. We have the LM2596 module, a few USB type
A breakout boards, and you would also need a DC jack to connect to the power adaptor.
First, let’s solder the DC jack to the input of the power module. When you switch ON the
power supply, the LED on the module should start glowing, we then connect a multimeter
in the DC voltage measuring mode and adjust the trimpot till the voltage output is about
5V. Once this is done, you simply need to wire the output to the individual USB connectors.
Before we do this, let’s talk about the enclosure.
I did not find a suitable enclosure that could be used for this project, so I went ahead
and designed a simple one that can house all the electronics. There’s a link in the description
if you’d want to use it. This is how all the electronics will fit in, so make sure
you use the correct wire lengths. Wire up all the USB ports and then power up the unit
to make sure you have 5V across them with the correct polarity.
Once this is done, it’s time to place the electronics inside the enclosure. You can
start by gluing the USB ports in place, followed by the power module and then the DC power
jack. I rewired the DC jack so that it’s positive terminal is close to the positive
input of the LM2596 module. Make sure you are happy with the final setup and then use
the top half to seal the unit as it has a lip and groove. The enclosure should fit together
nicely, but this will depend on the quality of the print, you can add a bit of glue to
hold it together.
This hub has 4 ports, but you also can buy these split USB cables that can be used to
connect up to 8 devices in total. As you’ve seen, this only distributes power and it will
not work with smart devices like your smartphone that also make use of the data lines for communication.
I would recommend that you only use this to power your DIY projects.
Before we conclude, let’s talk about the total cost to build this. First, we had the
power module, then the 4 USB ports, a DC power jack and finally, some wire and the enclosure.
That’s it for this video. We will continue building more DIY projects in the coming weeks
and several of them will also be USB powered. If you liked this video, then don’t forget
to like, share and subscribe, it helps massively with the YouTube algorithm. Thank you for
watching and I will see you in the next one.