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Logic analyzer capture, showing the rails constantly oscillating at a high rate

When Your Level Shifter Is Too Smart To Function

April 13, 2024 by 9 Comments

By now, 3.3V has become a comfortable and common logic level for basically anything you might be hacking. However, sometimes, you still need to interface your GPIOs with devices that are 5 V, 1.8 V, or something even less common like 2.5 V. At this point, you might stumble upon autosensing level shifters, like the TXB010x series Texas Instruments produces, and decide that they’re perfect — no need to worry about pin direction or bother with pullups. Just wire up your GPIOs and the two voltage rails you’re good to go. [Joshua0] warns us, however, that not everything is hunky dory in the automagic shifting world.

During board bring-up and multimeter probing, he found that the 1.8 V-shifted RESET signal went down to 1.0V — and its 3.3 V counterpart stayed at 2.6V. Was it a current fight between GPIOs? A faulty connection? Voltage rail instability? It got more confusing as the debugging session uncovered the shifting operating normally as soon as the test points involved were probed with the multimeter in a certain order. After re-reading the datasheet and spotting a note about reflection sensitivity, [Joshua0] realized he should try and probe the signals with a high-speed logic analyzer instead.

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Delays And Timers In LTSpice (no 555)

April 13, 2024 by 2 Comments

If you need a precise time, you could use a microcontroller. Of course, then all your friends will say “Could have done that with a 555!” But the 555 isn’t magic — it uses a capacitor and a comparator in different configurations to work. Want to understand what’s going on inside? [Mano Arrostita] has a video about simulating delay and timer circuits in LTSpice.

The video isn’t specifically about the 555, but it does show how the basic circuits inside a timer chip work. The idea is simple: a capacitor will charge through a resistor with an exponential curve. If you prefer, you can charge with a constant current source and get a nice linear charge.

You can watch the voltage as the capacitor charges and when it reaches a certain point, you know a certain amount of time has passed. The discharge works the same way, of course.

We like examining circuits for learning with a simulator, either LTSpice or something like Falstad. It is easier than breadboarding and encourages making changes that would be more difficult on a real breadboard. If you want a refresher on LTSpice or current sources, you can kill two birds with one stone.

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Crank-Powered Train Uses No Batteries Or Plugs

April 12, 2024 by 5 Comments

The prolific [Peter Waldraff] is at back it with another gorgeous micro train layout. This time, there are no plugs and no batteries. And although it’s crank-powered, it can run on its own with the flip of a switch. How? With a supercapacitor, of course.

The crank handle is connected a 50 RPM motor that acts as a generator, producing the voltage necessary to both power the train and charge up the supercapacitor. As you’ll see in the video below, [Peter] only has to move the train back and forth about two or three times before he’s able to flip the switch and watch it run between the gem mine and the cliff by itself.

The supercapacitor also lights up the gem mine to show off the toiling dwarfs, and there’s a couple of reed switches at either end of the track and a relay that handles the auto-reverse capability. Be sure to stick around to the second half of the video where [Peter] shows how he built this entire thing — the box, the layout, and the circuit.

Want to see more of [Peter]’s trains and other work? Here you go.

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Do You Trust Your Cheap Fuses?

April 11, 2024 by 34 Comments

When a fuse is fitted in a power rail, it gives the peace of mind that the circuit is protected. But in the case of some cheap unbranded fuses of the type that come in kits from the usual online suppliers that trust can be illusory, as they fail to meet the required specification.

[Andreas Spiess] has used just these fuses for protection for years as no doubt have many of you, so it was something of a shock for him to discover that sometimes they don’t make the grade. He’s taken a look at the issue for himself, and come up with an accessible way to test your fuses if you have any of those cheap ones.

It’s an interesting journey into the way fuses work, as we’re reminded that the value written on the fuse isn’t the current at which it blows but the maximum it’s intended to take. The specification for fuses should have a graph showing how quickly one should blow at what currents above that level, and the worry was that this time would be simply too long for the cheap ones.

In the video below the break, he looks at the various set-ups required to test a fuse, and instead of a bank of large power supplies, he came up with a circuit involving an 18650 cell and three one ohm resistors in parallel. The resulting 1/3 ohm resistor should pass in the region of 10 A when connected across the 18650, so with a 5 A fuse in that circuit and a storage ‘scope he’s able to quickly test a few candidates. He found that the cheap fuses he had were slower to blow than a Bosch part but weren’t as worrisome as he’d at first thought. If you have any of these parts, maybe you should take a look at them too?

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Emergency DIP Pin Repair For Anyone

April 7, 2024 by 20 Comments

Who has not at some point in their lives experienced the horror of a pin on a DIP package breaking off? It’s generally game over, but what if you don’t have another chip handy to substitute? It’s time to carefully grind away some of the epoxy and solder on a new pin, as [Zafer Yildiz] has done in the video below the break.

The technique relies on the pins continuing horizontally inside the package , such that they provide a flat surface. He’s grinding with the disk on a rotary tool, we have to say we’d use one of the more delicate grinding heads for something more akin to a miniature die grinder.

Once the flat metal surface is exposed, the chip is placed in a socket, and a new pin is cut from the leg of a TO-220 power device. This is carefully bent over, inserted in the socket, and soldered into place. The whole socket and chip arrangement is then used in place of the chip, making for something a little bulky but one infinitely preferable to having to junk the device.

There are many useful skills to be learned when it comes to reworking, and we’ve covered a few in our time. Most recently we saw a guide to lifting SMD pins.

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The I2C extender board on a white background, fully assembled, with two connectors and two indicator LEDs

Extenders And Translators For Your I2C Toolkit

April 5, 2024 by 5 Comments

If you’ve ever been laying out a network I2C devices inside a project box or throughout your robot’s body, you’ll probably know that I2C is not without its pitfalls. But for many of those pitfalls, there’s a handy chip you can use. [Roman Dvořák] from ThunderFly has experienced it on their drone building journeys, and that’s why they bring us two wonderful open source hardware boards: an I2C bus extender, and an I2C address translator.

The first board, an I2C bus extender, is based around the TCA4307 chip, and not only it lets you extend the bus further than it would normally go, it would also protect you. When the bus capacity is no longer handleable by your devices, or a particular misbehaving device gets the bus stuck, this chip will take care of it and dissipate your troubles. It will even let you know when your bus is wired up correctly, with a handy shine-through LED!

The second board is an I2C address translator. We’ve covered them before, but in short, address translators let you avoid I2C address conflicts while using multiple devices that share the same address. This particular module uses the LTC4317 chip, a common choice for such translation, and the board leaves no feature unimplemented. In the README, there’s quite a few pictures with examples of where this sensor proves mighty useful, too!

It appears that ThunderFly open sources a lot of their designs on GitHub, an effort that we salute. The designs are great to learn from, but if you’re just looking for turn-key hardware, you can get both of these boards from their Tindie store. The cables they use have locking connectors, but as long as the pinout matches, you should be able to solder a JST-SH socket and add these modules to your QWIIC toolkit.

Espressif’s ESP32-P4 Application Processor: Details Begin To Emerge

April 2, 2024 by 54 Comments

Every now and then there’s a part that comes along which is hotly anticipated, but which understandably its manufacturer remains tight-lipped about in order to preserve maximum impact surrounding its launch. Right now that’s Espressif’s ESP32-P4: a powerful application processor with dual-core 400 MHz and a single-core low power 40 MHz RISC-V processors. Interestingly it doesn’t appear to have the radios which have been a feature of previous ESP parts, but it makes up for those with a much more comprehensive array of peripherals.

Some details are beginning to emerge, whether from leaks or in preparation for launch, including the first signs of support in their JTAG tool, and a glimpse in a video from another Chinese company of a development board. We got our hopes up a little when we saw the P4 appearing in some Espressif documentation, but on closer examination there’s nothing there yet about the interesting new peripherals.

Looking at the dev board and the video we can see some of what the thing is capable of as it drives a large touchscreen and a camera. There are two MIPI DSI/CSI ports on  the PCB, as well as three USB ports and a sound codec. A more run-of-the-mill ESP32-C3 is present we think to provide wireless networking, and there’s a fourth USB port which we are fairly certain is in fact only for serial communications via a what our best blurry photograph reading tells us is a Silicon Labs USB-to-serial chip. Finally there’s large Raspberry Pi-style header which appears to carry all the GPIOs and other pins. We’ve placed the video below the break, if you see anything we’ve missed please tell us in the comments.

We first covered this chip back in January, and then as now we’re looking forward to seeing what our community does with it.

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