N8VEM single board Z80 computer


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


[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


[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


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.


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