About 30 years ago, before every computer had CD quality audio built in, audio cards and chips were technological marvels. MIDI chips, FM synthesis, and synths on a chip reigned supreme but one little device – just a handful of resistors – sounded fantastic. it was the Covox Speech Thing, a simple resistor ladder wired up to the parallel port of a computer that would output 8-bit audio to an external amplifier. [FK] recently built his own Covox (Czech, Google translatrix) with just 18 resistors, and the results sound fantastic.
Instead of fancy chips, the original Covox Speech Thing used the 8 bit parallel port on a PC. Back in the olden days, this was the fastest way to get digital data out of a computer, but since it was digital only, a DAC was required to turn this into audio. A simple resistor ladder was sufficient, and this hardware was eventually supported by the old DOS games from Sierra and Id.
[FK] has a demo of this LPT DAC available here, but we’re not thinking that link will last long. If anyone has a better link, leave a note in the comments and we’ll update this post. Thanks [beavel] for sending this in.
[Nathan Long] sent in two fairly simple mods he’s been working on. The first is the control of Woot-off Lights via LPT port. A computer checks Woot for the Woot-off logo, and if the logo is spotted, on go the lights. It’s really just a twist on the LED/Arduino email message system, but the creativity is nice.
His other modification is the stuffing of a Microsoft Intellimouse inside of a Logitech Wingman. With the goal of giving the old PS/2 mouse USB capabilities and removing the terrible ball. For those that are asking themselves “why bother? Terrible ergonomics, no scroll wheel, etc.” [Nathan] claims it’s for Quake 2 nostalgia, to each their own we suppose.
We see it all the time, a post based on an Arduino board with multiple comments calling it overkill. How exactly should you control your homemade peripherals if you’re not using a microcontroller (uC)? [JKAbrams] and [Tim Gremalm] answered that question with this printer port (LPT) adapter. They wanted an indicator light when someone in an IRC room was talking to them. By connecting a blue rotating light through a relay to the output of this fob they’ve done just that, but there’s room for much more.
The adapter uses a Darlington transistor array IC to protect the computer. A resistor between the LPT and the base pin on the chip ensures that current flow will be well within the safe levels for the computer. The Darlington transistor amplifies the output using an external power supply in order to drive heavier loads.
If you want a deeper understanding of the printer port check out this tutorial. LPT ports are becoming less common and that’s why so many projects are migrating over to USB (plus there’s no need for external power with most USB connected projects) but if you’ve got one, it’s probably not being used for anything else.
As many of you have mentioned, there are a lot of projects that are built with their own microprocessors, and are simply overkill. Here’s a reminder that we can do some pretty fun stuff light synchronized light shows without going overboard. This light show is controlled directly via the printer port on a computer. Sure you can’t un plug it and run it free standing, but you can build it for roughly $20.