Month: January 2009

N8VEM Single Board Z80 Computer

January 10, 2009 by 17 Comments

n8vem

The N8VEM is a homebrew computer project based on the classic Z80 microprocessor. It’s designed to be easy to build using large TTL DIP components instead of SMD devices. It runs the CP/M operating system and all drives are virtual in RAM/ROM. While the base hardware is interesting, we really like the potential for expansion using a backplane. Have a look at the project’s Hardware Overview to see extra boards like the bus monitor and the prototyping board. We found out about this project on [Oldbitcollector]’s blog; he’s using a Parallax Professional Development Board to create a VT100 terminal for the N8VEM.

Resistive Ladder Volume Control

January 10, 2009 by 26 Comments

preamp

[jefffolly] published some straight forward plans for a passive volume control. It uses a resistive ladder built across the contacts of 12W rotary switches. Each resistor provides a 5dB difference, and he recommends using 0.1% tolerance resistors to maintain accuracy. The use of discrete resistors instead of volume pots means that the output is much more predictable. All of the RCA sockets were connected using oxygen-free copper wire.

Wireless BlinkM Control

January 10, 2009 by 5 Comments

blinkm

[John] has been working with several BlinkM RGB devices. He’s created a controller to talk to each of the BlinkMs wirelessly and change their behavior. The core is an old relay tester box used to test telephone circuits. Each of its four knobs are connected to the analog inputs on the Arduino. The signal is transmitted using RFlink devices. Each BlinkM is paired with an ATmega168 and receiver. The control box also has a switch to send the same signal to all of the devices at the same time. The transmit and receive code are available on his site. You can find a video of it embedded below.

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DC Gearmotor Teardown

January 10, 2009 by 15 Comments

dcmotor

The RepRap project has made heavy use of the Solarbotics GM3 Gearmotor as part of their extruders. Unfortunately they’ve proven to be underpowered for the task and the plastic gears could cause future problems. [Zach] decided to investigate some other options. He bought a pile of motors from Kysan to try out. He posted a teardown of one of the motors on Flickr. He found it not only easy to disassemble, but the metal gears were also easy to put back together. Next up is testing it on the machine.

Intel 4004 Internals

January 9, 2009 by 15 Comments

The silicon wizards at Flylogic have certainly posted an interesting chip this time around. The Intel 4004 was the first widely used microprocessor. The logic gates are much larger than you’d find in modern chips. The unique feature is that each gate is designed to make the most efficient use of the silicon instead of the standardized shapes you find now. They’ve uploaded a full image of the chip.

For an introduction to silicon hacking, we reccomend [bunnie]’s talk from Toorcon and [Karsten]’s talk from 24C3. You can find many more posts on the topic in our silicon tag.

30’s Style Regenerative Receiver

January 9, 2009 by 11 Comments

radio

[Des] sent in this really cool writeup on building a Regenerative receiver using VFDs. Regenerative receivers are basically short wave radio receivers that use positive feedback to more finely tune the signal. Though they can be built with modern components, [Des] wanted to try to make something that not only looked like it was made in the 30’s, but actually used the same technology. He utilized some VFDs in various places where vacuum tubes were needed. After building, [Des] found that the unit performed very well, better than his authentic 30’s radio that he compared it with.  Those VFD’s seem to be everywhere recently. We did the story on using them as amplifiers, and and building display drivers for them too.

NoiseAXE Minisynth

January 9, 2009 by 8 Comments

3172157928_b226c6b2e0_o

The NoiseAXE is a miniature synthesizer based on the Picaxe 08M microcontroller.  Its operating principle is fairly simple: a conductive stylus touches the leg of one of eight resistors to play one of eight notes, while a photoresistor controls the amount of modulation, creating a variable vibrato effect.  While the synthesizer’s output is rather limited (the NoiseAXE isn’t exactly a Yamaha DX7), it’s still a pretty cool little project; you could use its unique sounds to add that gritty analog touch to your next electro hit.  Check out the video clip below to see and hear it in action.

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