I built a sound system for a friend, and programmed Philips RC5 remote control into the microcontroller. I recently ordered this remote:
To program:
- Press TV for 5 seconds until it lights up.
- Type 15526 as code
Author: halfgaar (Page 2 of 26)
Halfgaar is Wiebe. Wiebe is a contributing author on this weblog. He also has a lot of stuff (such as long, in-depth articles) on his personal website.
Wiebe works at YTEC, where he is a senior developer of customer-specific tailor-made software ("klantspecifieke maatwerk software") for clients in a few select markets: wholesale, printing and healthcare.
Here’s just a quick .gitconfig:
[core]
commentchar = %
[tig "color"]
date = cyan black bold
diff-header = cyan black
[tig]
ignore-case = yes
The colors are to make it readable on Windows Git Bash, because the dark blue is impossible to read.
And yes, I still have to set up my dotfiles github stuff.
At work, we had a small embedded PC that had a short in the mainboard. I attempted a fix, mostly for educational purposes. It wasn’t successful, but I wanted to post the method and result anyway. The method I used is elaborately explained on Youtube, so go hunt there for more details.
First I wanted to find the short. I opted for the method of connecting a current limited power supply and slowly cranking up the current till I can feel something heating up. To do so, I had to solder some wires to the input power jack first.
I set the supply to 1V and and started increasing the current. Given that small resistors have a rating of 250 mW, a 0.25 to 0.5 amps, giving 0.25 to 0.5 W, should be safe enough to gently heat up the shorted component. In the end, I had to increase the current to about 1.5 amps to detect a rising temperature.
I removed the cap in question:
Then I replaced it with hack (because I had no SMD parts here):
The short was gone, but it still didn’t power up. Then I gave up.
There is a bug in Konsole with tmux: lines often aren’t cleared properly. To fix, put this in tmux.conf:
set -as terminal-overrides ',*:indn@'
Just some example code for an nginx maintenance page:
server { listen 80; listen 443 ssl; server_name www.example.com; ssl_certificate_key /etc/ssl/temp/wildcard.example.com.key; ssl_certificate /etc/ssl/temp/wildcard.example.com.fullchainchain.crt; location = /503.html { root /srv/http/maintenance/; } location = /logo.png { root /srv/http/maintenance/; } location / { if ($remote_addr != 1.2.3.4) { error_page 503 /503.html; return 503; } } }
This is an interesting case. I made a sound system for a friend in 2012. In it is a soft-starter, that engages the heavy transformer through a ballast, so that the fuse doesn’t trip. This is it:
Up until today, I never knew he had to replace the fuse a few times a year. The reason I found out now, is because the amp wouldn’t start anymore; it would always blow a fuse. So, I was called in to repair.
This is the relay now, with charred contacts:
One initial thought of course is that the amp was turned off/on super quick, so the relay didn’t have time to disengage, subsequently connecting the mains directly to the unstabilized transformer. However, my softstarter design can handle quick off-on (although not super quick, I just tested), and he was adamant that it often happened after hours of off-time, and being careful not to bounce the switch.
My theory is that the mains AC sometimes arced over the relay on turn-on, so that the ballast would be bypassed, obviously blowing a fuse. This arcing slowly wore out the contacts, and probably made it more susceptible, ultimately resulting in always arcing. However, I use the exact same design in my own builds, and I never have this problem.
The relay is rated for 250 Vac, 30 Vdc. But perhaps with the mains in the right position, the transformer acts as a fly-back.
Interestingly, the relay contacts still read near-zero Ohms, and there is little to no voltage over it with when I test it with my 30V, 3A bench supply.
I now replaced it with a nifty relay (Amplimo LRZ) that has a wider gap, and tungsten pre-contact:
I’ll report back in a year how it held up.
I was researching how TVs pass through audio coming in from HDMI, and I found this. Just dumping it here as memory.
Just some quick links with the status of Spectre and Meltdown:
Just as a note to self mostly: this is an interesting article about the noise in a LM317/LM337 based power supply.
For Low ESR caps, one can use:
- Conrad 446063
- Conrad 445970
- Just get higher voltage and capacitance than you need (more surface plate area and thicker plates). This is a safer more flexible choice.
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