If your Arduino runs out of I/O lines, you can always add one of the several I/O expander chips that takes a serial interface to set its several pins. Or perhaps you could buy something like an Arduino Mega, with its extra sockets to fulfil your needs. But what would you do if you really needed more pins, say a thousand of them? Perhaps [Brian Lough] has the answer. OK, full disclosure: If you really need a thousand, the video isn’t exactly for you, as he shows you how to add up to 992 PWM outputs. The chip he uses works with any microcontroller (the video shows an ESP8266), and we suppose you could use two daisy chains of them and break the 1,000 barrier handily.
We like how short the video is (just two minutes; see below) as it gets right to the point. The PCA9685 chip gives you 16 12-bit PWM channels via an I2C interface. You can daisy chain up to 62 of the boards to get the 992 outputs promised.
Undoubtedly, the ESP8266’s biggest selling point is its WiFi capability for a ridiculously low price. Paranoid folks probably await the day its closed-source firmware bits will turn against humanity in a giant botnet, but until then, hobbyists and commercial vendors alike will proceed putting them in their IoT projects and devices. One of those devices is the Yeelight desk lamp that lets you set its color temperature and brightness via mobile app.
[fvollmer] acquired such a lamp, and while he appreciated its design and general concept, he wasn’t happy that it communicates with external servers. So he did the only reasonable thing and wrote his own firmware that resembles the original functionality, but leaves out the WiFi part. After all, the ESP8266 has still a lot to offer in its core essence: a full-blown 32-bit microcontroller with support for the most common, hobbyist-friendly SDKs.
The 60s and 70s were a great time for kitschy lighting accessories. Lava lamps, strobes, color organs, black light posters — we had it all. One particularly groovy device was an artificial rain display, where a small pump dripped mineral oil over vertical monofilament lines surrounding a small statue, with the whole thing lighted from above in dramatic fashion. If it sounds appalling, it was, and only got worse as the oil got gummy by accumulating dust and debris.
While this levitating water drops display looks somewhat similar, it has nothing to do with that greasy lamp of yore. [isaac879]’s “RGB time fountain” is actually a lot more sophisticated and pretty entrancing to watch. The time fountain idea is simple — drip water from a pump nozzle to a lower receptacle along a path that can be illuminated with flashing LEDs. Synchronizing the flashes to the PWM controlling pump speed can freeze the drops in place, or even make them appear to drip up. [isaac879] took the time fountain idea a step further by experimenting with RGB illumination, and he found that all sorts of neat effects are possible. The video below shows all the coolness, like alternating drops of different colors that look like falling — or rising — paint drops, and drops that merge together to form a new color. And behold, the mysterious antigravity cup that drips up and yet gets filled!
Allowances must be made for videos of projects that use strobes, of course. The effect of this time fountain and similar ones we’ve featured before is hard to capture, but this one still looks great to us.
Stick a 10kΩ pot in the left-side header and you can play a space shooter game, or make line drawings by twisting the knob like an Etch-A-Sketch. Be sure to check out the detailed walk-through after the break, and a bonus video that shows off Multiduino’s newest functions including temperature sensing, a monophonic music player for sweet chiptunes, and a virtual keyboard for scrolling text on the OLED screen. [Danko] has a few of these for sale in his eBay store. They come assembled, and he ships worldwide. The code for every existing function is available on his site.
You know the saying: “Dogs have people, cats have servants.” This is especially true when your feline overlord loses track of time and insists on being fed at oh-dark-thirty. You’re tempted to stay in bed feigning death, but that’s a tall order with the cat sitting on your chest and staring into your soul.
An automatic cat feeder would be nice at moments like these, but off-the-shelf units are pricey. [Mom Will Be Proud] decided to roll his own cat feeder, and the results are pretty impressive for what amounts to a trash can build. Two old food cans form the body — a Pringles can on top to hold the food and a nut can below for the servo. The metal ends of the cans nest together nicely, and with a large section removed from each, an aperture opens every time the hopper rotates, dropping food down a chute. A BeagleBone Black controls the servo, but anything with PWM outputs should do the trick. We’d lean toward the ESP8266 ecosystem for WiFi support for remotely controlling feedings, and we’d probably beef up the structure with PVC tube to prevent unauthorized access. But it’s a simple concept, and simple is a good place to start.
To find the scooter’s speed, he installed a magnet on the front wheel and a hall effect sensor on the fork to detect each time it passed by. Since the wheel is of a known circumference, timing the pulses from the sensor allows calculation of the current speed. A GPS receiver could be used if you wanted fewer wires, but the hall effect sensor on the wheel is simple and reliable. With the speed of the scooter now known, he needed to turn that into a signal the speedometer understands.
[James] wrote a program for an ATmega that would take the input from the wheel sensor and use it to create a PWM signal. This PWM signal drives a transistor, which alternates the speedometer sensor wire between low and floating. With a bit of experimentation, he was able to come up with an algorithm which equated wheel speed to the gearbox speed the speedometer wanted with accuracy close enough for his purposes.
While the software side of this project is interesting in its own right, the hardware is an excellent case study in producing robust electronic devices suitable for use on vehicles. [James] 3D printed a shallow case for the circuit board, and potted the entire device with black polyurethane resin. He even had the forethought to make sure he had a debugging LED and programming connector before he encapsulated everything (which ended up saving the project).
While the specific scenario encountered by [James] is unlikely to befall others, his project is an excellent example of not only interfacing with exiting electronics but producing rugged and professional looking hardware without breaking the bank. Even if scooters aren’t your thing, there are lessons to be learned from this write-up.
As cool as Nixies are — we’ll admit that to a certain degree, familiarity breeds contempt — they can be tricky to integrate. [dekuNukem] notes that aside from the high voltages, laying hands on vintage driver chips like the 7441 can be challenging and expensive. The problem was solved with about $3 worth of parts, including an STM32 microcontroller and some high-voltage transistors. The PCBs come in two flavors, one for the IN-12 and one for the IN-14, and connections for the SPI interface and both high- and low-voltage supplies are brought out to header pins. That makes the module easy to plug into a motherboard or riser card. The driver supports overdriving to accommodate poisoned cathodes, 127 brightness levels for smooth dimming, and a fully adjustable RBG backlight under the tube. See the boards in action in the video below, which features a nicely styled, high-accuracy clock.