Sunday, January 24, 2016

Portable Bluetooth Speakers

Back in 8th grade when I had a lot more time on my hands, I always wanted to build a decent pair of speakers.
I had built several speakers back then already: some were literally just speakers with an amplifier circuit, all exposed
some were speakers people threw out and I modified them
most of them were just ugly, delicate, and not presentable or usable in everyday conditions.

This folder of links has been on my Google Chrome browser for 4 years:

The links that I told myself I would look at eventually:

As you can see, building speakers is a very involved process. This is probably the reason why I did not go forth with this project back in 8th grade: the amount of things I needed to consider were daunting and I put it off.
  • I would need to consider how much money I wanted to spend on what type of amplifier circuit: Class A? B? C? D? each class gives a different sound quality, but A is much more expensive than D, and much less power efficient. It's the difference between vacuum tube amplifiers, and a regular transistor based amplifier:
  • I would need to consider the shape of my speaker and the structure inside. There are two ways to approach this: a ton of trial and error or a ton of math.
  • I would need to consider what material I would build my box out of. Should I use the acrylic sheets I have lying around, or should I invest in MDF board for higher sound quality?
So I never took the time to consider all these things.

Yesterday I looked at the project again for the first time. I realized that sometimes you need to stop thinking and just do: otherwise you stay stuck. 
Here are the plans for the speaker:
  • Triangular prism shape (like a Toblerone box)
  • Build out of acrylic sheet, covered with faux leather
  • Wooden end caps 
  • two speakers in the front, two tweeter speakers on the side
  • Class D amplifier (This time around I don't think I want to get involved with figuring out circuitry, so I'm going to use a prebuilt Class D amplifier, the PAM8403. It's low voltage, cheap, and relatively high quality)
  • Bluetooth and auxiliary connectivity!
  • 2600mAh rechargable battery
It might not be the highest quality or the most optimal design, but it's better to start something than to not do anything at all.

Here is the progress so far.

You need an 11" x 14.75" sheet of acrylic

Some random trash for dampening the inside of your speaker box (this is so that when the speaker shakes, the whole speaker box doesn't shake and cause distortion)

Speakers and tweeters

Switch, PAM8403, some nuts, LED + resistor (for power indication), 100uf capacitors for the high pass filter for tweeters

Cut the sheet to size

mark down where you need to bend it (for the equilateral triangle shape)

mark out where you need to cut the holes for the speakers

nice fit!

attempt to bend plexiglass

 This is where I stopped.
Along with needing to acquire a bluetooth module, a battery, leather, wood, and an audio jack, I also needed to buy a heat gun.
Usually when I bend small pieces of plexiglass I use a cigar torch lighter:
I don't have a nichrome wire heating element to bend a whole sheet this large...
For now this project is at a pause, but I will keep updated on the progress!

Sunday, January 10, 2016

Printing on Lighters

In a previous post I showed how to engrave a metal lighter:

If you tried this method on a disposable lighter, the lighter would probably burst. You'd be making the walls thinner on a plastic container that's already under a bunch of pressure.

So what if you want to customize your a lighter?


This is the first one lighter I personalized. (those splotches are totally intentional)

The second lighter I tried (the fading was not intentional)
Inspired by this Vic Mensa:
The story behind "SAVEMONEY":

The method I used was similar to the way t-shirts are silkscreen printed. Just a stencil and some paint.
This particular lighter I'm printing for a friend :D

Get a lighter. 
The Dollar Tree sells lighters at a really nice price. Bic Lighters usually cost $1 - 2.
At the Dollar Tree, a pack of three lighters costs $1. The also come with adjustable flame in case you needed to use your lighter as a flamethrower for self defense.
A pack of two Scripto lighters (better quality) also costs $1.
Things generally cost $1 at the Dollar Tree.

Get a design down. Featured above, common slang used in San Francisco.


Break out the scissors and gluesticks!

Glue the cut out onto the lighter. Make sure it's firmly impressed onto the lighter on the position you want.

Use an X-Acto knife to cut out horizontal lines first. Cut from left to right.

After that, cut from top to bottom.

All the letters removed. 

Apply your sister's nailpolish.

After it dries for 30 minutes, rinse the paper portion of the lighter under water. I don't think you want to submerge the whole lighter if you want it to work in the future.

When the paper is wet, it's a lot easier to peel off. The gluestick glue also dissolves in water, which is a big help.

 After all the paper is peeled off, scratch off any blemishes and apply a coat of transparent lacquer (clear nailpolish)!

And now you just wait for it to dry.

This method isn't only applicable to lighters. You could print on anything you shouldn't engrave or want color on, like your TI N-Spire, your phone case, etc.
In the near future I think I would like to try printing some logos. Maybe I can start selling some Gucci Chanel Rolex lighters...

I hope you learned! If you try this out, please post pictures of what you made!