Your fancy white electronic brick of consumer electronics started off white, but after some time it yellowed and became brittle. This shouldn’t have happened; plastic is supposed to last forever. It turns out that plastic enclosures are vulnerable to the same things as skin, and the effects are similar. When they are stared at by the sun, the damage is done even though it might not be visible to you for quite some time.
Continue reading “Yellowing: The Plastic Equivalent Of A Sunburn”
1976 was the year the Apple I was released, one of several computers based on the MOS 6502 chip. MOS itself released the KIM-1 (Keyboard Input Monitor) initially to demonstrate the power of the chip. The single board computer had two connectors on it, one of which could be used for a tape recorder for long-term storage. When [Willem Aandewiel] went to the Apple Museum Nederland in 2016, he saw one and felt nostalgic for his youth. He was able to get a replica, the microKIM, and build it but he wanted to use new technology to interface with this old technology, so he decided to use an ESP8266 as a solid state tape recorder.
One of the reasons the KIM-1 was so popular when it was released was that there was lots of documentation available. [Willem] used this documentation to figure out how the KIM-1 saves data to the recording device. An ATTiny85 is used to decode the pulse stream that the KIM-1 sends when saving because the timing was too tight to both “listen” and decode the bits as well as convert and store them. For loading programs, the data can be sent digitally as 1’s and 0’s to the KIM-1. This means that the ATTiny is only used for decoding and doesn’t have to re-encode the data. Because of this, saving is slow, but loading is very quick.
To complete the project, [Willem] added four buttons, one each for rewind, record, play and fast-forward, and a screen so you can see which program is currently selected and can go from one program to another. As a nice throwback touch, record and play have to be pressed at the same time when saving. For more 6502 projects, check out this 6502 based DIY computer, or this 6502 built from discrete parts.
[Mohamed Sami] built a syringe pump out of Meccano building set parts. It consists of a simple framework with a DC motor mounted on it that actuates the syringe when powered. A check valve harvested from an ordinary household spray bottle keeps the syringe from sucking back liquid that it has just pumped out, so it can keep pumping forever. A lead-acid battery powers the whole thing.
Syringe pumps are typically used to deliver precisely measured quantities of substances. Right now [Mohamed]’s rig is just an uncontrolled pump, but he hopes to get a better understanding of and control over how much liquid gets pumped. Adding an encoder to the DC motor would be a start, was his thought — or even better would be a stepper.
You’d be surprised how many syringe pump projects we publish. Not just another syringe pump, but simple hydraulic projects and even using the syringe barrel as a logic probe’s enclosure.
