Light Pen Draws on LED Matrix

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Who needs a 1920×1080 OLED display when you can have an 8×8 matrix of LED goodness? That’s the question [Kathy] asked when she built this LED matrix light pen project. It looks simple enough – a 64-LED matrix illuminates as the pen draws shapes. But how does the circuit know which LED is under the pen? Good old fashioned matrix scanning is the answer. Only one LED is lit up at any time.

[Kathy] used a pair of 74LS138 3-to-8 line decoders to scan the matrix. The active low outputs on the ‘138 would be perfect for a common cathode matrix. Of course [Kathy] only had a common anode matrix, so 8 PNP transistors were pressed into service as inverters.

The pen itself is a phototransistor. [Kathy] originally tried a CdS photoresistor, but found it was a bit too slow for matrix scanning. An LM358 op-amp is used to get the signal up to a reasonable level for an Arduino Uno to detect.

The result is impressive for such a simple design. We’d love to see someone use this platform as the start of an epic snake game.

Basic IKEA Wall Light Turned Smart and Colorful!

WallLight-DSO

[Daniel Grießhaber] just finished his latest electronics project and we love it. He’s taken a cheap IKEA wall/ceiling light and completely revamped it with RGB LEDs and intelligent control!

The light he used is called the LOCK, and is a mere 1.79€ or about $4 USD. It has lots of room inside and a nice frosted glass dish which results in some excellent color diffusion. He’s designed a nice big circular PCB to mount inside off of the original mounting points. To do this, he used Eagle software to create the circuit and his trusty desktop CNC to mill out the pattern.

To control the lights he used an old ATMega8 board he had lying around, with the Arduino IDE and WS2812 Library. He’s outlined all the parts, diagrams and program sketches you’ll need to make your own over on GitHub.

Unfortunately the LEDs aren’t quite as bright as he hoped so it can’t be used to replace a regular room light — instead he plans on turning this project into sunrise timing light in one of the bedrooms — still pretty cool!

VU Meter Record Player Lights it Up

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[Michaël Duerinckx] was given a turntable for his last birthday from his fiancée — since then he’s started collecting records like nobodies business. But about a month ago he started itching to do an electronics project — he decided to upgrade his record player to include a VU Meter!

As he began designing he soon realized he didn’t have all the tools he needed to do this project right — a perfect excuse to go check out his local makerspace, SoMakeIt!

He started prototyping the VU Meter on a breadboard, and opened up the record player – it was like this thing was made to be hacked. Two free connections off the power supply to power his circuit, bingo! [Read more...]

Press Button Get Party Mode

partymode2_2 If you’re looking to do something awesome with a graphing calculator, [Chris] is the guy to go to. He’s literally written the book on the subject. His PartyMode project, however, has absolutely nothing to do with calculators. It’s a fantastic display of lights, colors, and sounds that has been rebuilt again and again over the years, and something [Chris] has finally gotten around to documenting.

The idea for [Chris]‘ PartyMode is a single button that will transform a room from a boring computer lab or dorm room into a disco with 22.4 channel sound, and computer displays used as panels of color. The first version began in the lab in his school’s EE department that included ten CRT monitors. There were a few VUFans featured on the good ‘ol Hackaday, but a few problems with regulations and politics brought this version of PartyMode to a premature end.

The second version is a miniaturized, ‘press a button, get a party’ setup with a crazy number of RGB LEDs, a few more of those computer fan VU meters, and a Bluetooth app to control everything. Unlike the first version, the PartyMode 2.0 is fully independent from a computer, instead relying on an ATMega to do the audio processing and handling the Bluetooth interface. Judging from the videos below, it’s quite the site, and if you need an instant party, you could do much worse.

[Read more...]

Here Come the RGB LED Clones

ws2812 and clones timing

It seems like every third project on Hackaday uses WS2812 RGB LEDs in some way. We all love our blinkenlights, and bright, cheap, serial controlled RGB LEDs are the bees knees.

As with all products these days, competing manufacturers have discovered the huge market for these things, and clones are now available. [Tim] recently took a look at the PD9823, as well as three versions of the WS2812. [Tim] is considered something of a WS2812 guru here at Hackaday. You might remember him from his WS2812 driver optimization article, which should be required reading for any WS2812 hacker.

As many of us know, the timing characteristics for these LEDs can be a pain to work with. The values also differ between the WS2812S and WS2812B. [Tim] discovered that the new through hole WS2812D parts are different yet again, though rather close to the B parts. The PD9823’s designers must have studied the WS2812’s closely, as their 190ns time base falls directly between WS2812S 166ns time and the 208ns time of the WS2812B. The PD9823 also requires a slightly longer reset pulse.

The takeaway is that well written drivers such as [Tim's] should have no problem with the new parts, but compatibility is something to keep in mind as more clones hit the market.

The 200 LED Ring Clock

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There are LED clocks, and then there are LED clocks that can blind you from 30 paces. [Stiggalicious's] LED ring clock is of the latter variety. 200 WS2812B/Neopixel RGB LEDs drive the ring clock to pupil searing levels. The clock runs on ATMega1284P, with timekeeping handled by an NXP PCF8563 real-time clock chip. Code is written in Arduino’s wiring language using Adafruit’s Neopixel library.

Building the clock with a single Printed Circuit Board (PCB) would be both expensive and wasteful. [Stiggalicious] cleverly designed his clock to be built with 8 copies of the same PCB. Each board makes up a 45° pie slice of the ring. All 8 PCBs have footprints for the CPU, clock chip, and other various discrete parts, but only the “master” section has these parts populated. 7 “slave” sections simply pass clock, data, power and ground through each LED. He used Seeedstudio’s board service to get 10 copies of his PCB made, just in case there were any mistakes.

[Stiggalicious] rolled the dice by buying exactly the 200 LEDs he needed. Either he got really lucky, or the WS2812 quality testing has improved, because only one LED had a dead blue LED.

If you’d like to find out more, [Stiggalicious] gives plenty of details in his Reddit thread. He doesn’t have a webpage setup for the clock but he’s uploaded his source code (pastebin link) and Altium schematic/PCB files (mega.nz link). We may be a bit biased, but hackaday.io would be a perfect spot for this or any other project!

5000 Lumen LED Projector? Naw, How About a Whopping 1 Candela?

1 candle projector

One of our readers recently found a ASK Proxima C170 (also sold as the InFocus LP600) in the waste bin, thrown away because it stopped working — He snatched it up and decided to try tinkering with it. A visual inspection quickly found the problem, a 100uF cap had blown!

He replaced the capacitor and got the projector to turn on again without much difficulty. Not wanting to pay a few hundred dollars for a bulb he’s ordered a 5000lm 50W LED array from China to give it new life as an LED projector, because as it turns out it’s a fairly simple hack to trick the projector into thinking it has an official lamp in it. It’s just a matter of shorting a few leads on some of the photo-couplers!

In fact, once this hack is done, you can use any kind of light source you want! So just for kicks he decided to try using a tea light candle. It actually managed to project an image on the wall thanks to the optics of the projector! Functional? Not really, but it’s a cool way to prove a successful hack towards an even cooler end project though!

For other fun projector hacks, check out this roundup we did a few years ago.

[Thanks thefamoushat!]

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