Developing stuff

The dumb AP in the garage is a nexx WT3020, minuscule "travel" router that happily runs OpenWRT. There was a problem with the most remote stations (esp8266 nodes with MongooseOS apps) "giving up" on coming back online, once they faced too many connections drops.

This mod:

Resulting in this:

brought the following improvements:
| Station | Signal before | Signal after | Improvement | |-------------------|---------------|--------------|-------------| | b8:27:eb:6f:cd:a3 | -58 | -56 | 3.4% | | 84:0d:8e:51:d1:47 | -68 | -56 | 17.6% | | dc:4f:22:95:39:7d | -76 | -70 | 7.9% | | cc:50:e3:b5:b3:38 | -84 | -76 | 9.5% | | 5c:cf:7f:02:66:98 | -70 | -60 | 14.3% | | 8c:aa:b5:06:1b:e9 | -64 | -62 | 3.1% | | 5c:cf:7f:11:ab:d9 | -74 | -60 | 18.9% | | cc:50:e3:b6:8e:ac | -100 | -86 | 14.0% | | 8c:aa:b5:05:55:a9 | -76 | -70 | 7.9% | | c8:2b:96:11:79:2f | -88 | -82 | 6.8% | | ec:fa:bc:6f:0c:a5 | -92 | -84 | 8.7% |

The stations further away had the best results. Which was the problem I was solving.

For a project I needed a Raspberry with a screen, preferably in compact package. While researching the options, a comment mentioned the quality of the picture of those screens so I decided to try it.

As usual there are clones of clones of those around, but the instructions that work are at the wiki of WaveShare here: 4" HDMI IPS

The screen works fine on a Raspberry 3 I have. What I wanted to have and was missing on others similar displays I have is not only to blank the screen, but also to turn off the LED back light. There is a physical switch to turn off the light, but that does not make a lot of sense if you want to embed this thing into a box. There is a single IC that looks like a DC/DC and most probably is the LED constant current controller. It is 5 pin SOT-23 package with markings N66J. Searching for that I found only links in Chinese on sites related to parts sourcing, but no datasheets were linked.

I searched around for 5 pin LED boost controller IC, and looked at datasheets, while probing with a multimeter if the pins of the actual IC match those described in the documentation. Finally there was somewhat of a match - TI LM3410. Such boost controllers usually have a current setting resistor of a low value, input and output capacitors, inductor and a diode. If there are additional components they could be a small capacitor to set the oscillation frequency and eventually a resistor to control the dimming pin, usually pulling it to a defined state to fully on. There was only one additional 10k resistor connecting a pin to input voltage pin.

From a youtube video I saw someone else doing the same and mentioning that pin 8 of the main IC that deals with HDMI - TFP401A is sync detect and will be pulled low if there is no signal. A perfect match! The led IC will be stopped when there is no signal from the PI. Adding hdmi_blanking=1 to /boot/config.txt will be allow screen blanking to be triggered by power management, which will then pull low pin 8 of the IC which will turn off the screen backlight.

Here is a short youtube video I uploaded

I came up with a new design for the lamps and one of the best was a gift to my wife:

Finally the repository is available at this address on Bitbucket

As previously mentioned I have some love for reusing nicely routed pieces of aluminum.
Finally when thousands of circumstances came together we shot this video.

Shot @BetaHaus & @home.

One of the first PCBs I designed and ordered made was for a 8x8 LED matrix backpack. I ordered 5 matrices on ebay once and ever since had different ideas what to do with them, but always put away the project, because I just did not want to bother with all the wires and prototyping boards my previous projects were made of. And I wanted something small and reusable.
So after some time I had the idea to build a backpack for the board.

Work in progress, but at least source code is available at:
Google Code Repo for CycLed