In this video we’ll be building a stylish
desktop volume knob, which, besides looking really cool, allows you to finely control
the loudness of your music in a tactile way. As you can see, the knob itself is made out
of concrete, so feels pretty solid. The design is also completely customisable, so you can
match it to your desk setup. Here for example I used plexiglass for the
base, and added an LED to give it a ring glow, which looks really cool. If you do customise yours and want to share your results with others, then why not check
out this week’s sponsor which is a completely free app called Maker Amino. It’s very relevant
to you guys as it’s a community app for everyone who is interested in DIY, 3D printing, technology
and electronics etc. You can discuss ideas and collaborate, vote on your favourite builds
and projects, and actually learn too using the Maker Catalogue, which is an incredibly
useful encyclopaedia of all things DIY. So again, it’s called Maker Amino and is available
on iOS and Android. I hope I see you over there!
Right, so the first thing we’ll work on is the base. You can use a variety of different
materials for this, and in my case I’m using a piece of 12mm thick oak.
To cut out the base we’ll need a special hole cutter bit. This can be adjusted to cut a
circle with a size of your choosing, and is pretty inexpensive.
Once you’re about half way through the wood, flip it over and begin cutting from the other
side. This gives you a cleaner cut, though it’s still pretty jaggy so we need to give
it a sanding down. To do this we’ll get a bolt that fits perfectly
inside the central hole, and then clamp it in place with a nut and washer. We can now
lock this into a drill and spin it over some sandpaper until it’s perfectly smooth. If
you give it some time it can look really good. Now what we need to do is get a bit that matches
the size of the potentiometer we’ll be using, which in most cases should be 18mm. This potentiometer
by the way is what actually adjusts the volume, and I’ll be covering it in more detail in
a sec. This bit can then be used to expand the central
hole to make room for the potentiometer’s body. However, as there are pins to one side,
we need to use a coping saw to make room for them. After you’ve done this, the potentiometer
should now fit snugly inside the base. All we’ve got to do now is cut a grove for
the wires to be threaded through later. The easiest way to do this is to use the coping
saw to cut completely through. However, as my oak platform is thick enough, I thought
I’d use the opportunity to try using a router., which is a tool I’ve actually not used that
much. This is just a cheap one that I’m borrowing, so should represent what you guys can also
do at home. After securing my base in place using the
wood it was cut from and some double sided tape, the first step was to adjust the height
of the bit so that it protruded about a millimetre. I then carefully slid the bit between my marks,
with the router faithfully carving it out for me.
The bit was then lowered another millimetre, and the cut deepened a little more. This was
repeated until it was 6mm deep. So, whether you use a router or just use a
coping saw, the base should now be complete. One thing we’ll do before we move on however
is place it upside down onto a piece of thin cardboard and mark and cut out an identical
shape, with a rough hole in the middle. This will be later used as a spacer when it’s time
to add the concrete. Now we can start working on wiring it up,
which brings us back to the potentiometer. As audio is usually stereo, we’ll need one
that is dual gang, meaning that there are two stacked potentiometers in a single unit.
It also needs to be linear, rather than logarithmic, and have a value of 500ohms. As these are
a little tricky to find, I’ve placed links to a suitable one in the description.
Now, to transport the audio signal we’ll need a USB cable. It doesn’t really matter what
connection it has on either end, as these need to be chopped off so we can access the
wires inside, but the fact that USB cables have 5 individual wires makes them perfect
for this project as we need to transport the audio both TO and FROM the volume knob.
So, after trimming the wires we need to group them into two sets so that we wire them up
correctly later. Here I’m grouping white with red for one audio
channel, and black with green for the other audio channel. The ground wire can be just
left on its own. These are now ready to solder to the potentiometer.
With the shaft facing upwards, the rightmost pin is the audio input, the middle pin is
the audio output, and the pin on the left is the ground.
This applies to the bottom set as well, only they’re on a separate circuit.
So we’ll solder the first set of wires to the top most pins, with red on the input,
and white on the output. We can do the same for the bottom pins, only
this time using the black wire on the input, and the green wire on the output.
The ground wire can then be soldered to both the top and bottom pins on the left.
With that wired up we can now add the audio connectors, but before we do we can decorate
the wire with some braided sheathing. This stuff is really inexpensive and is available
in a variety of different colours. I’m going to go with a muted yellow to be somewhat colour
coordinated with the base, but you can go with anything you like.
To fit it over the cable we’ll first chop off the other end and then feed it all the
way along the wire until it’s about 2cm away from the potentiometer.
We can then chop off any excess from the other end. As this sheathing is liable to fray however,
we need to seal it by melting it slightly with a match. Now we can shift it down to
reveal the wire a little, pushing it right up to the potentiometer on the other side
in the process. Now we can slide on some heatshrink to use
later – don’t forget to do this at this stage because we can’t add it after we’ve soldered
on the connectors. Now we can separate the individual wires into
the same grouping we used earlier, so white with red and black with green.
As you can see I’ve cut the white and green wires slightly shorter to help avoid short
circuits with their adjacent pair. Now we need to get a headphone extension cable.
It doesn’t need to be long, but I do recommend going for something of reasonable quality
because cheap ones tend to break quite easily. So, after chopping it exactly in half, we’ll
get the male connector and expose its wires. These can then be soldered to the red and
black wires, which, if you remember, are the wires we soldered to the input pins on the
potentiometer. Once that’s done we can get the female connector
and solder this one to the white and green wires instead, which this time go to the output
pins on the potentiometer. When you do this, make sure you solder the
same colour wires of the headphone extender to the USB wire sets, so that the audio channels
don’t get flipped. As you can see, because the wires are at slightly
different lengths it’s impossible for them to touch and short out. So, after wrapping
them each in electrical tape, the last thing to do is connect all of the ground wires together.
This too can have electrical tape wrapped around it, and then we can slide up the heatshrink
we added earlier and carefully use a match to shrink it around the cables.
Once that’s done the potentiometer can be glued inside the base using some epoxy. When
you do this, make sure that there’s no chance of the glue to entering the small gaps in
the sides of the potentiometer, which would damage it, and also that the shaft is perfectly
vertical whilst it sets. Once it has set it’s time to add the concrete,
which is where this build gets particularly fun.
The first thing we can do is can add our cardboard spacer and then wrap the whole thing in cling
film to stop any moisture from reaching the wood.
Now we can mould some blue tack around the potentiometer’s shaft so that, again, moisture
is prevented from seeping down inside. Once that’s done we can get some thin flexible
plastic, like a piece of laminated paper or something from product packaging, and stick
it to the perimeter of the base using some tape, which gives us a mould into which we
can add the concrete. For this we’ll need some sand, cement, and
a container to mix it all in. We’ll do a two to one mix, so for every two spoons of sand
we use, we can add one spoon of cement. As we don’t need that much of it, eight spoons
of sand and four spoons of cement should do the trick.
Once it’s all mixed together we can begin adding the water. Be very careful with this
as it doesn’t want to be too sloppy. Try and get it to the consistency shown here.
It’s important that the mould remains perfectly level whilst the cement dries, so we’ll put
it on top of a cup so that the cling film doesn’t get in the way.
The cement can now be added, using a spoon to prod it into the corners, and you need
to add enough so that it comfortably covers the potentiometer shaft.
Now we can give it a bit of a tap to level it off. As the plastic might not be keeping
perfectly circular however, you may want to insert a disc that’s same size as the base
to keep it in line. Here I used a base from a previous attempt.
Optionally, if you’d like the top to have a super smooth finish, you can place another
piece of plastic down on top of it whilst it dries.
The difference this makes is quite significant to the final look, as it can trap air bubbles
and make it look more interesting. Without the plastic, it looks more like stone, so
just choose the style you prefer. Either way, once it’s set we can peel back
the plastic to reveal its sides. Now we can carefully pull it off as we’ve still got to
remove blue tack from the bottom, and the cling film and washer from the base.
Now we can glue the knob back in place using epoxy. However, to stop it from dripping down
the shaft and making it stiff we’ll to this upside down. Also, don’t forget to have another
piece of thin cardboard between the wood and concrete so that it dries level.
Now all that’s left to do is try it out. So we can plug the audio jack into the audio
source, in my case a computer, and then plug speakers or headphones into its audio socket.
The volume on the source can then be set to maximum, which gives us the most volume range
to work with, and it’s then ready to use. It really does work a treat, and evenly controls
the volume from minimum to maximum when used with either headphones or speakers.
Now feel free to use different materials too. You don’t have to use hardwood for the base,
for example. You could use some MDF and then paint it, for example. Or even use some plexiglass
like I did here, though you’ll need to get this one cut with a CNC router as it won’t
be that easy to get a good finish by hand. You could even add an LED for some illumination.
If you want to do this, it’s just a case of gluing an SMD LED face down, and running two
extra wires in parallel with the audio cable. The other end of these can have a resistor
added, the value of which can be calculated with an online calculator, and then they can
be soldered to the red and black wires of a spare USB cable, making sure that the polarity
is correct. When plugged in, the LED should light up whenever the computer is on.
Whatever you choose to do I hope you gave a good time building one, as it’s really fun
working with concrete like this and is great to show to your friends.
Now before I sign off, I’ve made a poll on the Maker Amino app I mentioned earlier about
which video I should make next. If you’d like to have a say, simply download the app, which
is free, and search for the term ‘diy perks’ to find the poll, and then submit your vote.
I’m pretty interested in finding out what you guys would like, so do head over there
and let me know. So that’s it for this video. I hope you’ve
enjoyed it, and as usual, don’t forget to hit that like button and maybe consider subscribing
if you haven’t already. So, other than that, I’ll see you next time! Bye for now.