Building a ’60s guerilla homebrew square wave generator

What do you do when you’ve got three broken function generators? Build your own, obviously. Since your workshop has already gone through three of these bad boys, you might find yourself repairing your build. Better not use any fancy ICs and go with a transistor only build.

When [Miroslav] sent in his ‘guerilla homebrew’ square wave generator, we were really impressed. With a relatively simple schematic that uses parts that could be salvaged from old radios, this is a real MacGyver build.

The generator is based around a simple astable multivibrator. It doesn’t provide sine waves, but it’s the easiest circuit to get working. The build started off with a quartet of 2N4401 transistors, but according to the datasheet and the venerable Tektronix 502A, these had a very bad rise time compared to 2N3904s.

[Miroslav]‘s project generates square waves up to 2.22 MHz and pulses with a variable duty cycle from 1-49% and 51-99%. Output is either 5 Volt TTL levels or an adjustable 0-3.38 level. The generator is exactly what [Miroslav] needed, so that makes it a great tool in our book.

Reverse engineering a Korg Monotribe

Yesterday, Korg released a firmware update to their ribbon controller synth, the Monotribe. The firmware is just an audio file that needs to be played to the sync input of the box. [gravitronic] thought this was rather interesting, so he decided to decode the monotribe firmware. It’s the first step to custom Monotribe firmware, and on the path towards reverse engineering this neat box.

After converting the firmware update to a .wav, [gravitronic] looked at the file with a hex editor and found that each sample is two bytes, and the left and right channels are the same. That made enough sense, so after getting rid of one channel, he sent it through Python to take a look at the patterns of ones and zeros.

Of course, [gravitronic] arbitrarily chose high = 1, low = 0, and little-endianness. The first result didn’t produce a nice “KORG SYSTEM FILE” in the header, so he tried other combinations until the output file looked reasonable. The result is the actual .bin file that’s going to serve as the basis for a nice homebrew firmware. You can grab [gravitronic]‘s Python script here and decode your own firmware.

10 Meter long moving light show is mesmerizing


[Marcus] was recently commissioned to put together the electronics for a slick 10 meter long LED installation at the Hsinchu Biomedical Science Park Exhibition Center in Taiwan. While you might assume that he was asked to construct a large LED matrix, this project is a little bit different from what you probably expected.

The display is actually a long light tunnel made up of 30 moving triangles suspended from the ceiling. The triangle movement is governed by 60 separate stepper motors, while the lighting is provided by 30 HL1606 RGB LED strips he picked up from Adafruit. The display’s logic is handled completely by an XMOS controller, which is beefy enough to handle controlling all of the stepper motors and the LEDs simultaneously.

After he hand assembled all of the motor driver boards and tested things in his workshop, the whole lot was shipped over to Taiwan for assembly by the on-site crew. After a bit of troubleshooting, they were able to get things working properly, and the display looks great as you can see from the image above.

[Marcus] says that he doesn’t have video of the display in action just yet, though he will update his post whenever he does.

[Thanks, Paul]

Hackaday Links: December 3, 2011

Honey, would you like some cheese? WHIRRRRRRRRR

[The Timmy] broke his manual cheese grater. It would be a waste to throw away a perfectly functional tool that’s only missing a handle, so he kicked it up a notch with a cordless drill. Now [Tim], “can grate with incredible speed and power for even the toughest of cheeses.” Anyone have a broken pepper mill?

The most adorable oscilloscope

We’re not much for plugging products, but this scope is really cool. It’s designed to fit on a breadboard and is smaller than some ICs we’ve seen (68000, so yes, it is). We’re wondering why there hasn’t been a homebrew version of this yet.

Now do an R/C castle

Here’s a minifig-sized R/C LEGO car made by [brickmodder]. It has a custom drive train and steering mechanism that uses the smallest servos [brickmodder] could find. How about an R/C pirate ship next?

It’s probably an ad for something

Here’s some sort of code thing that asks the question, “Can you crack it?” Apparently, it’s for UK cryptanalyst recruiting. You won’t get a 00-designation, but woo Bletchley Park.

Inverting an inverter

[Manfred] is putting an alternative energy setup on his land. Of course he needed an inverter to charge his batteries, so he went with a highly regarded (high price) box. What he got was anything but. You’re going to need at least ten minutes to go through this hilariously sad teardown of a high quality Taiwanese inverter. Oh, [Manfred] is awesome. Just look at his microhydro plant.

RCA DSB772WE teardown shows that this cheap streaming box might have potential


[David Anders] wrote in to share some details of a cheap little gadget he picked up at his local Wal-Mart. He scored the RCA DSB772WE media streaming box for $48, and so far it looks like it could be a promising addition to his living room.

He started a project page for the box, detailing some of his findings thus far. The device is MIPS based and runs the Linux kernel version right out of the box. The networking components are based on the Broadcom BCM7615 chipset, though it looks to [David] that the Ethernet jack was removed at some point during production.

So far, he’s managed to get a serial console running on the device, along with an additional USB host connection. That’s about all the poking around he has done thus far, but seeing as the box can output a 1080p signal over HDMI, it could be a cheap substitute for an Apple TV or similar device.

If you happen to have one of these at home, or are planning on buying one, be sure to check out his project page and contribute any information you might be able to glean from it. We’re sure [David] would appreciate it, and we certainly look forward to seeing what else comes out of his hacking adventures.

Weekly Roundup 12/3/11

In case you missed them the first time around, here are our most popular posts from the past week.

In first place was a repeat from last week of how you can make a privacy screen from an old LCD display. We want to serve up fresh stuff in this post though so we’ll add one to our top five this week.

Coming in at second place is a post about [Alex's] real-life Star Trek door that opens and closes pneumatically. Live long and Prosper [Alex]!

Following up in third place is a post about a proposal to build 100 government-run hackerspaces in China. Surely there will be bureaucracy and red tape involved involved with such a thing but maybe the U.S. could take a note about this and help us stay competitive with the rest of the world.

Next we have a post about a project where [Brainiac27] built a 1300 lumen bike light. For those of you who don’t follow the latest in lighting trends, that is like having a 100 Watt spot light mounted to the front of your bike!

Following that, take a look at this post about [FXI Technologies]‘ new dongle that lets you run android on any computer or HDMI television. This thing is the size of a thumb drive and yet packs some pretty serious fire power.

Finally, if you are looking for an interesting way to work with plastic, take a look at this post where you are shown how to make prosthetic parts using old soda (or pop if you are one of THOSE people :) ) bottles.