Saved By The Bel — Understanding Decibels

If you’ve hung around electronics for any length of time, you’ve surely heard of the decibel (often abbreviated dB). The decibel is a measure of a power ratio. Actually, the real measure is a bel, but you almost never see that in practice. If you are versed in metric, you won’t be surprised to learn a decibel is 1/10 of a bel. Sometimes in electronics, we deal with really large ratios, so the decibel is logarithmic to cope with this. Doubling the number of decibels doesn’t double the ratio, as you will soon see. It’s all about logarithms, and this ends up being extremely useful when measuring something like antenna or amplifier gain.

Besides antennas, decibels are often used to measure sound and light. The reason is that human ears and eyes have a logarithmic response to those quantities. Your ear, for example, has a huge dynamic range. That is to say, you can hear a whisper or a space shuttle launch. That ratio is about 1 trillion to 1, but that’s only 120 dB. This is also why potentiometers made for volume controls have a logarithmic taper. A linear pot would seem off because, for example, a tenth of a turn at one extreme will affect the apparent volume much more than a tenth of a turn at the other extreme. This holds true whether or not those knobs go up to eleven.

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Paul: A Robot And Its Ball

[Jochen Alt]’s Paul is one of the coolest robots of its type, and maybe one of the coolest robots period. Personality? Check. Omniwheels? Check. Gratuitous feats of derring-do? Check. Paul is a ball balancing robot.

Under the hood, Paul isn’t all that strange. He’s got two microcontrollers, one for taking care of the balancing and kinematics, and another that handles the LEDs, speech processor, loudspeaker, remote-control, and other frilly bits. But the mathematics! Paul is a cylinder standing up on top of a bowling ball, so the only way it can roll forwards is to lean forwards. But of course, it can’t lean too much, because it has also got to balance. It’s absolutely the least reasonable means of locomotion. We love it.

[Jochen] was nice enough to put everything up on GitHub, so you can see how it was done, even though it looks like magic. And we dare you to watch the video, embedded below, and not feel at least a pang of sympathy pain when (spoiler alert!) he falls flat on his face. Does he recover? We’d love to know!

Paul is just one of the stellar robots in the 2017 Hackaday Sci-Fi contest, so head on over there if you still don’t have your fill.

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Fixing Fake FTDIs

If you know where to go on the Internet, you can pick up an FTDI USB to Serial adapter for one dollar and sixty-seven cents, with free shipping worldwide. The chip on this board is an FTDI FT232RL, and costs about two dollars in quantity. This means the chips on the cheap adapters are counterfeit. While you can buy a USB to serial adapter with a legitimate chip, [Syonyk] found a cheaper solution: buy the counterfeit adapters, a few genuine chips, and rework the PCB. It’s brilliant, and an excellent display of desoldering prowess.

Why is [Syonyk] replacing non-genuine chips with the real FTDI? The best reason is FTDIgate Mk. 1, where the official FTDI driver for Windows detected non-genuine chips and set the USB PID to zero. This bricked a whole bunch of devices, and was generally regarded as a bad move. FTDIgate Mk. 2 was a variation on a theme where the FTDI driver would inject garbage data into a circuit if a non-genuine part was found. This could also brick devices. Notwithstanding driver issues, the best reason for swapping out fake chips for real ones is the performance at higher bit rates; [Syonyk] is doing work at 3 Mbps, and the fake chips just don’t work that fast.

To replace the counterfeit chip, [Syonyk] covered the pins in a nice big glob of solder, carefully heated both sides of the chip, and slid the offending chip off when everything was molten. A bit of solder braid, and the board was ready for the genuine chip.

With the new chip, the cheap USB to serial adapter board works perfectly, although anyone attempting to duplicate these efforts might want to look into replacing the USB mini port with a USB micro port.