Collie147 on Mining And Refining: Cobalt, The Unfortunately Necessary Metal.That kid on Kodak Film Factory Revealed.smellsofbikes on Teardown: Cooler Max Liquid Cooling System.Andy on Barilla’s Open Source Tool For Perfect Pasta.Texas Bred on Laser Engraving, Up Close.Andy Pugh on Mining And Refining: Cobalt, The Unfortunately Necessary Metal.john brown on Kodak Film Factory Revealed.smellsofbikes on Ebike Charges In The Sun.Hackaday Podcast 189: Seven Segments Three Ways, Candle Code, DIY E-Readers, And The Badge Reveal 3 Comments Maybe they attribute the tingly effect to owning an Apple product, I dunno.Īnother offender is electric blankets: they capacitively couple to you, and if you reach out to touch a grounded object or a partner not under the blanket, you get a tingly feeling in the fingertips. Most people don’t notice it until you explain it. Macbooks in particular are an egregious example of this: if you use the “travel” adapter with no ground the computer’s metal chassis wrist pad floats at 50-60V and you get a persistent low-level tingling effect. Definitely detectable if you’re paying any attention, but not hazardous. With the capacitance in the line filters in modern SMPS, it amounts to 10-20 microamps. It’s pretty low current, limited by that stray capacitance. If you touch that “live” chassis and provide a path to ground, you’re shunting that half line voltage to ground. Uh, you should realize that any device plugged into the wall with just a 2-wire (no ground wire) cord does exactly this: the chassis is coupled to both hot and neutral through stray capacitance, and tends to float at around the halfway point. * Is the need specifically for serial, or will something else (eg Ethernet) which has inherent isolation suffice? If there is a device which has such a high ground potential, and is capable of sourcing sufficient current to be dangerous, then I’d be significantly more worried about the safety of the operator * What is causing the safety concern –> This is actually the biggest concern. * Why weren’t existing commercial products sufficient? Given that RS232 / 422 / 428 etc are more than capable of handling this sort of scenario, the more interesting questions are therefore around the application: ![]() So, from that perspective, your comment is somewhat uninformed, not to mention downright rude. Safety issues only arise when the internal resistance of such a source is sufficiently low to drive significant currents. Ever felt a tingle from your laptop when you touch it and a ground at the same time? Most modern ungrounded electronic devices with metal chassis (laptops, tablets, hifis, etc etc) can float you well above local ground potential when you touch them. ![]() Posted in Peripherals Hacks Tagged null modem, serial, usb Post navigationĪ difference in ground potential is not necessarily an issue at all. If you’re looking for other useful applications for USB-serial devices, there’s plenty – you can even try your hand at software-defined radio! While it’s not something everyone will need, for those that do, it should come in handy. Expect to see devices available on Tindie in future for those that need a hookup. originally created the device to solve a specific problem at his day job, but community response was large enough that he was kind enough to share the project online. This is important, as it allows two computers at different ground potentials to be safely connected to each other without damage. ![]() Rather than directly connect the lines, however, they pass through an opto-isolator. The TX and RX lines are cross-connected to allow communication between the two sides. The device consists of two USB Communication Device Class, or CDC chips, creating a USB serial port for each attached computer. needed just such a tool, but one that would work in a modern USB environment. Largely eliminated in daily use by the advent of home networking, there are still fringe applications where such a thing can come in handy. The classic serial null-modem cable was, among other things, used to connect two computers together for communications and file transfer.
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