The 1/2 watt LM386 Audio Amplifier

I love the LM386. It’s a complete amplifier in an 8 pin DIP chip! All that is needed to build an audio amp are a few external components most of which are decoupling capacitors. It is well suited to low power applications and runs just fine on a 9 volt battery or any voltage supply from 4-12 volts. It has a low quiescent current drain of only 4mA so it won’t kill a battery right away if you leave it on and idle. The gain is internally set to 20 but the addition of an external resistor and capacitor between pins 1 and 8 will increase the gain to any value from 20 to 200. An increase in bass frequency can be facilitated by adding a 10K resistor and .033 uf capacitor in series between pins 1 and 5.

The parts list for this build is pretty minimal:
1 – Enclosure of your choice
1 – 10 ohm resistor
1 – 10K potentiometer
1- 220 uf polarized capacitor
1 – 100 uf polarized capacitor
1- 10 uf polarized capacitor
1 – .01 uf ceramic capacitor
1 – .047uf ceramic capacitor
2 – 1/8″ mini audio jacks
2 – 1/4″ audio jacks
1- 9 volt battery clip
1 – 9 volt battery
1- small perforated circuit board
Some hookup wire
A speaker of your choice for output.

I suggest building the circuit on a bread board first. It’s much easier to troubleshoot and find errors and you can easily experiment with different components. You’ll also learn more as you can see what each component does by removing it or changing its value. You can leave the audio jacks off the output and install some small binding posts or just two wires with alligator clips on them for connection to an external speaker. You could also put the whole circuit in a larger enclosure and install the speaker for an all in one portable amp.

This amp can be used to amplify any low level audio signal like an mp3 player or even a guitar or bass as you’ll see in the video.

All of the parts required can be found at Radio Shack and shouldn’t cost more than $20. Have fun building your amp and keep on hackin!

The Chicken Tractor

Happy Earth Day!
Perfect timing for my latest project, the Chicken Tractor. A Chicken Tractor is a movable chicken coop without a floor. It allows the free ranging of chickens where ever the tractor is moved too. They have access to the ground where there’s grass and bugs and dirt, three things chickens love! They also get the benefits of fresh air, sunlight and exercise. The tractor can be moved over a garden or flower bed area prior to planting to help fertilize the soil and clear it of weeds, hence the term tractor.

This tractor was built to house six little “bitty” chickens for now. Later, I’ll build two more with two birds in each one. They’ll eventually have a chicken coop where all six can roost and lay eggs, which should start happening around August. The total materials cost of this project was about $45.

The video below is another time lapse build. It’s a long one, but it’ll show you ALL of the steps involved to make your own. You’ll enjoy the antics of my dogs and cats as they hang out in the shop with me during the build.
Thanks for watching and keep on hackin!

Hack #3, The Talk Box.. for bass

Anybody over 35 remembers Peter Frampton and his talk box on the “Frampton Comes Alive” album. It sounded awesome!

He wasn’t the first one to use this device however. Pete Drake had and album in 1964 that featured a “talking” steel guitar

I’ve always wanted to try making one, so.. this week’s hack is just that, only it’s for a bass guitar instead.
A typical Talk Box consists of a speaker in a totally sealed enclosure with a tube coming out of it which carries the sound. The tube is runs up a mic stand and ends near the mic. It extends past the mic a few inches and goes inside the mouth of the musician. The sound from the guitar or other instrument comes out of the tube and resonates in the mouth cavity, then gets reflected into the mic. The shape of the mouth determines the timbre of the sound and so by altering the shape of the inside of the mouth one cane produce a wah wah type effect or a talking effect.

A bass sound signal is quite a bit different from a guitar sound signal. A guitar is in the higher frequencies which means it has more energy due to more cycles per second. It’s pretty easy to get that sound to run through a tube but a bass signal doesn’t provide enough energy to make a loud enough sound to work with using this method.
I came up with something that does work however. It came to me in the middle of the night. I woke up and suddenly thought, “hey, why not just mount a small speaker up on the mic and run a very short tube from that?” So, I did just that and it works great! The speaker is a tiny thing that came from a cell phone and the amp that drives it was hacked from a Sony radio cassette player.

Watch the video and you’ll hear how it sounds. I’m having fun playing with it!
If you’re a musician and you like to tinker, you should try building a talk box. They’re lots of fun.
Happy Hacking!

Work Bench Build for the Hack A Week Shop!

Here it is, hack #2!

It’s a work bench I’ve made for my new shop. I used 2″ x 2″ lumber for the frame with one 2″ x 4″ under the work surface to help stiffen it over the 8′ span. The sheets of wood are OSB (oriented Strand Board) which is inexpensive and strong. It’s made from strips of wood chips glued and pressed together. The sheets I used are 5/8″ x 2′ x 8′ and cost about $8 per sheet. I used 1 5/8″ drywall screws for most of the assembly and a few 3″ drywall screws at the corner points. The paint is Glidden Porch and Floor paint and costs about $21 per gallon. I had the light fixture already but they can be purchased for about $25 with bulbs and come with a plug in cord. I installed two power strips with the leads running out the rear of the back board.

I wanted a place to put my oscilloscopes up and out of the way yet in a place that I could easily access and see them when in use. I decided to make an overhead suspended shelf for them. This design keeps the area below them free to be used while working on projects.

The whole bench cost less than $100 to build and I put it together in two evenings time. I really like the large work area and overhead lighting. All that is needed now it to mount my tool rack to it and it’s ready to use!

Here’s some drawings with dimensions if you’d like to build this bench. I’ve omitted the o-scope shelf.

Here’s the time lapse video of the build:

Dead trees and ink…

I’m a pen and paper sort of guy. I like to draw up my plans in isometric view on paper. It takes only minutes and I have an idea of what materials I need. Yes, I could use a drawing program for this and there are many… even a 3-D program like Google Sketchup… but I like the feeling of drawing. It’s the first phase of the idea in my head being output to the physical world through my hand.

The drawing below, of the work bench I’ll be building, took about 5 minutes to execute. It has all the dimensions and it gives me an idea of what I might want to change. I used this drawing to make a materials list and then went to Home Depot and bought everything I need for about $83. I’ll be getting started on construction this evening around 6:30 pm EST and you can watch on my Ustream channel here:

Of course, I’ll be shooting video of the build to edit into the next Hack A Week video which will be posted Friday evening.

The plan...