Category Archives: Electronica

IV22 clock software

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This post discusses about the basic software architecture as it at the publish date. I’ll update it as things change over time.
I’ve decided to use the Arduino environment for it’s existing libraries.

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Category: IV22 clock

IV22 clock hardware

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Some time ago I got my hands on some IV22 VFD tubes.
They’re quite large 7 segment displays with the specific greenish-blue color

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Category: IV22 clock

Samsung SyncMaster 940NW repair

Several days ago a friend gave me 3 defective displays that were in the dumpster at his office. They where complaining that the image was unstable, they where shutting off, etc.

That made me curios if the CCFL’s where dying or they had some power supply problems, as all 3 are very old monitors with a lot of run hours

Disassembling them revealed that at least the power supply had better days. Most of the low voltage capacitors where faulty.

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Inokim Light 2 electrical repairs

After disassembling my Inokim Light for a spring-clean-up I’ve found out that it has severe water damage inside, after running on wet roads all autumn, and getting submerged once in a deep puddle.
It looks like, because of the shape of the frame, front lid placement and the synthetic sponge used to secure the battery, water pooled on the bottom of the unit and remained there for a long time.
Also, no care was given for connector protection.

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Category: e-PushBike

Fixing a VORTEX 32G19

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This is a quick post about fixing a TV that had the HDMI connector melted off the main board.
Got the TV as junk – so there was no pressure to fix it.

The TV’s id numbers are ( stickers on the main board / firmware, etc):
C/N: PC07035
P/N: CV028E_V5E0_01238
D/N: 20070322X00005
M/O:J03A117
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Category: Repairs

Ao-to

Un scurt istoric despre dezvoltarea Ao-to

Incepand cu 2015 m-am ocupat de primele generatii de hardware pentru proiectul Ao-to, descris aici: Ao-to
In link-ul respectiv gasiti o descriere detaliata a modului in care Razvan a ajuns la cerintele specifice proiectului si link-uri catre toata documentatia proiectului, impartita pe etape.


Proiectul e bazat pe un microcontroller STM32F407V, un accelerometru LIS302DL si ceva electronica de suport: drivere pentru servo-uri, LDO si toata reteaua de filtrare, cateva switch-uri discrete ca decupleaza alimentarea extensilor nefolosite, etc.
Intreaga “magie” e in codul si modelele matematice facute de Razvan.
Intregul proces de dezvoltare a fost iterativ, pe masura ce am descoperit probleme sau Razvan a avut idei noi.
De asemenea, nu toate variantele de design au avut si implementare practica.
Pentru primele 2 generatii rolul meu a fost de schematic + pcb designer si constructia / depanarea prototipului la nivel de HW.
Pentru a 3-a generatie Razvan s-a ocupat de design, eu am avut doar partea de review si montarea prototipului.

Generatia 1

Generatia asta a fost faza de validare a intregului concept hardware si software.
Tinta a fost sa includ toate functiile cerute de Razvan si sa reduc cat se poate de mult suprafata cablajului.
A trecut prin cateva iteratii in care am redus dimensiunile, rearanjat componentele si imbunatatit informatiile de pe silkscreen.


au devenit




Aceasta varianta a fost folosita pentru a monta primele prototipuri:


Cu ocazia asta am gasit si cea mai serioasa problema de design: footprint-ul tranzistorilor alesi pentru a comanda canalele de servo nu se potrivea de nici un fel cu tranzistorii cumparati.
Am decis sa fac un mic hack si sa montez tranzistori in SOT23-5 “dead-bug”:

Nu arata frumos, dar a fost suficient pt a valida intreaga idee.

Generatia 2

Acest set de placi este cel care a fost inclus in proiectul de pe kick-starter ao-to-one
Modificarile majore: modificata partea de comanda sa utilizeze doar tranzistori in capsula SOT23-5, rearanjat conectorii si aranjarea componentelor pe placa.


Acest set de documentatie a fost folosit pentru a realiza primele prototipuri oficiale, cele folosite pe kickstarter:

Din pacate proiectul de pe kickstarter nu a avut succes.

Generatia 3

Aceasta iteratie a fost o varianta “mini” a intregului proiect, cu un pcb mai mic si doar o parte din functionalitate.
A fost conceput ca un “main-board” care contine microcontroller-ul si electronica de baza.
Pe main-board se conecteaza placa cu senzori.


Pcb-urile produse arata asa:



Proiectul a ramas in aceasta faza datorita lipsei de timp.
Sper ca documentatia sa fie indeajuns pentru reproducerea proiectului de cei interesati.
Eventual o sa incerc sa raspund la comentariile de pe aceasta pagina.

Category: Ao-to

Control board

The 3’rd in the series is the control board.
It’s purpose is to allow easy interface from a single-board computer that has one SPI and one I2C port.
Also, it provides a common reference clock and a synchronous update signal to the two DDS boards, as required by AN-587
The SPI port is level-shifted to a MCP23S17-E/SP SPI to parallel expander.
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Category: VNA

AD8302 detector

The second board in the VNA is the phase / frequency detector.
For this one I chose an AD8302 chip.
It will measure in the range I’m interested in.
It might not be the best part for this, but for the initial design it’s enough, as it works out-of-the box.

The board contains:

  1. two low-pass filters, identical to the ones used on the DDS boards
  2. a fixed 30dBm atenuators for the reference input
  3. two switched 30dBm atenuators for the DUT input
  4. a AD8302 detector
  5. a MAX11612 12bit ADC to read the detector
  6. LDO, passives and decupling for the active components
  7. transistors and diodes to drive the two atenuators switching relays

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Category: VNA

AD9851 signal generator

The signal generator is based on the AD9851 DDS chip
The board contains:

  • AD9851 chip and passives
  • 2 5V LDO’s for the digital and analog DDS power supplies
  • footprint and passives for a local 30MHz oscillator, for stand-alone use
  • 50MHz low-pass filter copied from the N2PK VNA project:
  • several footprints for atenuators
  • a 1:2 50ohm power spliter
  • 2 gain blocks based on the MSA-0286 MMIC amplifiers
  • different connectors for RF / CLOCK / power / DDS data

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Category: VNA

General description

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Hello

While working on RF stuff I got to the point where I had to tune filters and measure frequency response of amplifiers and other tuned circuits.
This implies having access to a VNA.
As something like that is out of reach, and buying an existing one is out of my budget I started out designing one from scratch.
For that I’ve used the N2PK VNA as a starting point with some small changes that I though will be useful.

The entire system will have:

  1. Two AD9851 based generators, each with 2 buffered outputs
  2. One AD8302 based detector that measures phase and amplitude differences
  3. One system control board, that offers to the driving computer a SPI and an I2C interface



Each board has a 12V input and local LDO’s for all needed voltages.
12V was chosen because the value of the MMIC’s bias network was high enough to require just a generic inductor.
I’ve used 5V for all internal supplies as all chips used that voltage.
Also, I’ve used a common PCB template – so the boards can be stacked with M3 spacers.
That will also simplify making some shielded cases, if needed – just one case template.

The overall system architecture looks like this:

Category: VNA