Multiplexing – all fun and games

Everyone basically knows how to use a seven segment display. Either the anodes or the cathodes are connected together and the others are each connected to a pin on the microcontroller. With a Arduino nano this looks as follows.

Via multiplexing and half an hour of soldering practice you’ll get something along the lines of this:

and since multiplexing is fun, here’s the button matrix that goes with the 7 segment output board:

Both boards are driven with SN74HC595 shift registers and some BC547 NPN-transistors for the ground switching. Nice little shenanigans to play around with arduinos.

ESP8266 Program Adapter Hack

So I bought this really cheap Programming Adapter for the ESP8266 I had laying around. Only problem is, to program the ESP8266 it needs to be switched into programming mode, which means GPIO0 has to be connected to ground during initial powering.

Since I didn’t want to fiddle around with wires each time I’m trying to program this module I simply soldered a pcb tactile switch to GPIO0 and GND Pins of the programmer. So just hit the button before and while plugging the device in. You can let go of the button as soon as the red led indicates the ESP8266 is being powered.

Here’s a picture of my masterpiece in case you want to build your own. Happy tinkering.

Upcycling with 3D-Printing – Raspberry Pi Blower Fan

This is another showcase of 3D-printing for a project I’m working on. So I’ve had this old broken laptop laying around. The thing is probably 20 years old and had this huge blower fan in it. I already threw the old enclosure away but I’ll show you what I did to the fan and the newer enclosure which fits the Raspberry Pi.

Here are the pics:

I cut the fan out of it’s existing cage and glued it to the bottom of this 3D-printed one.

The top part actually consists of a flat part which I painted with nail color. I then added the logo slide which is only 0.6mm thick. (If anyone would try to donate a multi-color 3D printer I’ll happily oblige..)

To regulate the fan speed a little additional circuitry is needed. For those playing along at home I made the layout for a PWM-transistor thingy that allows for a range bigger than just turning the fan on or off. Schematic is as follows:

This is a simple n-channel mosfet, in this case a zvn4306a that I had laying around. The 10k-resistor is needed to drain the gate capacitance of the FET. The motor actually survives voltages higher than 5 volts, but since it’s connected to a raspberry pi and this is the highest voltage we can get without tinkering, we’ll just use that.

Waveshare 7″ 1024×600 HDMI Display in Raspbian – Part 2: Hardware

Well hardware is kinda overstating it. I designed a (simple) adapter to screw the raspberry pi to the back of the screen. Basically I started with two rectangles. One for the pi and one for the screen. Every edge had a hole(M3 for the screen and M2.5 for the Pi) to attach the devices to it. Then cut away some material. Well, pictures are worth a thousand words.. There you go:

This adapter is printed in PLA with a 20% infill and a 0.2mm layer height on my Robox RBX-1. It’s plenty strong to support the pressure on the screen under normal use. The pi then goes onto the back of this. That’s all there is to say. File’s attached to the post. Have fun.


Waveshare 7″ 1024×600 HDMI Display in Raspbian – Part 1: Software

This one doesn’t actually deserve much Text. I got the display from here. If you wanna connect the display to the raspberry pi, go to the console on the pi and type:

sudo nano /boot/config.txt

Add the following codes to the end of the file:

#Settings in /boot/config.txt for the 7" Waveshare 2.1 Display in Raspbian
# set current over USB to 1.2A
# HDMI config
# 1024x600 display
hdmi_cvt=1024 600 120 6 0 0 0

Hit CTRL+x and proceed by clicking the y-key.  One reboot later and you should be all set. Happy Coding!

Cheap DIY DMX-Controller

DMX-Controllers cost too much. Actually they’re not as expensive as other audio-gear but still…

So I’ve taken matters into my own hands and created this, a 5 Fader DMX-Controller with USB-Interface for the cost of lousy 25 bucks. If I find the time, I’ll draw up a schematic. But ’till then enjoy the pictures.

Happy tinkering!