I have many things connected to my single computer monitor via HDMI. I use a HDMI switch so I don’t have to unplug and replug cables all the time. But my cheap $6 HDMI switch is an unpowered passive switch, so it has problems working when the video source does not provide enough power to the switch.
For example, when my Mac Mini is plugged in, the 5V pin only supplies about 3 volts. Inside of the switch is a set of diodes and a AMS1117 voltage regulator that is supposed to output 3.3V using 5V, but instead it is only outputting about 2V. This made the LEDs in the switch flicker and blink (which seemed like a symptom of a bad power supply) and switch refused to function (no video output). My solution was to add a USB micro connector so I can add an external 5V power supply.
After adding the power supply, the switch is able to function properly with a steady supply of power.
I don’t really like my “third-hand” tool so I decided to build a better one using flexible ball-jointed coolant spraying pipe hoses. It’s not a totally new idea, SparkFun even sells some of these parts as a kit. But my way is slightly better, and I got the hoses from eBay (look for “Flexible Water Oil Coolant Pipe Hose for Lathe CNC”) instead because SparkFun’s prices were excessively expensive.
I am currently working with Adafruit on Trinket stuff, because of my experience with USB and V-USB. Recently I wrote a bunch of simple tutorials and libraries for Trinket:
this is a very long and detailed tutorial that I did a long time ago, check it out!
search term: mp3_alarm_clock
This is a LED pocket watch. It has 12 LEDs to show the hour, 60 LEDs to show the minute, and 60 LEDs to show the second. The LEDs are arranged in three rings. There is a button on the top to activate the pocket watch, and a button on the back to change modes and settings.
The battery is a rechargable lithium ion coin cell battery and it is charged from a micro USB connector. The battery life depends on how heavily the pocket watch is used, but if you leave it alone, it is estimated to last several months. There is a low battery indication feature. This pocket watch also feature a buzzer and a vibration motor, which are used for the alarm feature, and the motor causes a short “tick” as each second passes by. The pocket watch is constructed of a PCB, two pieces of laser cut clear acrylic plastic, and a 3D printed casing.
Click Me!! More instructions, pictures, animations, and videos.
search term: ledpocketwatch
As I get more serious into my electronics hobby, I need to work with more SMD components. Some component packages are very difficult or impossible to solder with a traditional soldering iron. To solve this problem, I decided to hack a toaster oven to become a reflow soldering oven.
This page is from my old website, and it is sort of popular, so I’ve moved it here.
A USB HID report descriptor is one of the descriptors that a USB host can request from a USB device. HID devices send data to the host using reports, and the descriptor tells the host how to interpret the data. I will try to show you how to write one of these descriptors.
On my old website, the article “MMC/SD Card and FAT Tutorial” was really popular (it still holds almost top ranking on Google). However, the information there is so old that most of it is obsolete. Elm-Chan’s FatFs library has been updated many times since then, rendering some of the old webpage I wrote obsolete. But I will put up some of the old content here so you may still see it.