PiVPN for Raspberry Pi is a wonderful and easy OpenVPN setup tool. I use it a lot with various devices to access my home network. But it suddenly stopped accepting connection from those various devices. This is how I solved the issue…
This is what /var/log/openvpn.log showed:
Wed Jan 23 20:09:47 2019 126.96.36.199:24592 VERIFY ERROR: depth=0, error=CRL has expired: CN=tim
Wed Jan 23 20:09:47 2019 188.8.131.52:24592 OpenSSL: error:14089086:SSL routines:ssl3_get_client_certificate:certificate verify failed
Wed Jan 23 20:09:47 2019 184.108.40.206:24592 TLS_ERROR: BIO read tls_read_plaintext error
Wed Jan 23 20:09:47 2019 220.127.116.11:24592 TLS Error: TLS object -> incoming plaintext read error
Wed Jan 23 20:09:47 2019 18.104.22.168:24592 TLS Error: TLS handshake failed
So… The certificate has expired.
Replace flash memory
I want to use the Sonoff Basic with the mega-version of ESPeasy. This firmware does not fit in the 8 Mbit flash memory that’s standard on the boards. So I replaced the memory chip with a 32 Mbit version (Winbond W25Q32JVSSIQ). I bought the memories from RS Components.
It does, however, require some soldering skills.
Under ‘Tools -> Advanced’ enable ‘rules’
The Tektronix TDS 520 is a digitizing oscilloscope from the early 90s. It offers 500 MHz analog bandwidth, 500 MS/s sampling rate, 2 full-featured channels and 2 auxiliary channels with a limited vertical sensivity. Although being at age nowadays, this oscilloscope has perfect properties for a prominent place in the shack at home.
My TDS 520 was saved from the scrapheap.
Every (home)lab needs a good variable powersupply and so does mine. I wanted to design something with a microcontroller to set the voltage and current limit. Using a microcontroller also brings the possibility to use an LCD and fancy rotary encoders for control. The control loops themselves are pure analog.
I made this powersupply mostly from components I already had.
When I wanted to gently interface an incremental rotary encoder with an 8-bit Atmel AVR microcontroller, I couldn’t find a nice example. That’s why I wrote this little text. Many other howtos, manuals and descriptions are fuzzy, incomplete or too complicated to do the (easy) job.
This article describes three things: the hardware (just the minimal hardware) and two pieces of code. The first is just a simple interrupt based program and the other uses timers to make bigger steps when you turn faster.
I use Atmel AVR studio as IDE and the Through hole USBprog to program the microcontroller.
The idea to build a tube amp arose at a party, where all good ideas start. It stayed just an idea for about two years, due to other important things. This winter (2008/2009) the amp got my attention again. So I bought some books, googled for examples, searched explanations and gathered other info. Arnova and I then developed the first drafts for the amp. Later we visited some electronics fairs to get tubes and sockets. I have to be honest, eventually I bought new transformers and tubes. At the fairs I couldn’t find any proper power or output transformers, suitable chokes and half of my EL84 were bad. Reconsider buying old(er) parts.