Archivos en la categoría 'Electrónica'

SYPHCOM: CO2 meter

Lunes, Agosto 16th, 2021

This is my last week project: a Simple Yet Powerful Handheld CO2 Meter. SYPHCOM (name in progress ..)

The use for a portable CO2 meter is to be able to measure air quality in closed spaces (i.e. the office). The higher the number (usually above 1200~1500) the worst ventilation, which means higher chances to get
the Covid-19.

CO2 Meter Front View

CO2 Meter Front View

With this is possible to know when is time to open the windows and ventilate.

It’s main guts are:

Back view of handmade CO2 meter

Back view of handmade CO2 meter

The capacitor stands for when the CO2 sensor does a read cycle (every 2s): both the display and the SenseAir S8 uses so much power that you can see the display and leds in the Arduino Pro Micro sighly dim off when powered from standard USB 0.5A when a read is made in the SenseAir CO2 Sensor. Without the capacitor, the arduino can’t stand for the display refresh and does a glitch in the display.

BCO2 Meter Glitch

CO2 Meter glitch

Also there’s a UDN2981A source driver to drive the columns in the HDSP-2000 display and a small momentary press button with 10K pull down resistor to launch sensor callibration if pressed on powerup (use with caution!!).

CO2 Meter first working stage

CO2 Meter first working stage

The components that makes it portable are:

  • Lithium battery charger (Like this one).
  • Recycled Li-Po cell (250mAh)
  • Pololu s7v8a adjustable step-up DC-DC (adjusted to 5V).
  • Switch.
Making CO2 Meter porable with lipo charger and battery

Making CO2 Meter porable with lipo charger and battery

I use the same components to make projects portables. The good thing about the pololu s7v8a is that it is both a step-up and a step-down DC-DC converter. This is handful if a project work 3.3v as it will give 3.3v always even if the battery is reading 3.0v. Unfortunally the recicled 250mAh battery is not much for the power needs so only lasts 30m on thi battery cell.

CO2 Arduino HDSP-2000 SenseAir Schematic

CO2 Arduino HDSP-2000 SenseAir Schematic

Code available here.

In the video the leds seems to be dimmer than they really are because of the high light, but actually they are pretty much visible.

Overall all makes a nice looking portable and easy to use CO2 meter and Covid prevention tool in closed spaces.

Expired RSA SecurID Token revival (guerrilla hack)

Lunes, Enero 25th, 2016

I had lying around an expired RSA SecurID with the typical blank display only showing a small 3 in the right.

Looking for some info about expired tokens I found an old topic at flickr (original URL here) where Travis Goodspeed managed to revive one the tokens with a simple trick: apply 3v for a second in two of the pads behind the protective plate.

Here is the diagram:

Expired RSA SecurID Token Revival Diagram

Expired RSA SecurID Token Revival Diagram

Here the revived Token:

Expired RSA SecurID Token Revived

Expired RSA SecurID Token Revived

The token was expired since november 2011 but still got battery to keep working.

I Haven’t tested if token still is valid to autenticate against RSA daemon after revival.

Broken Kindle 3

Lunes, Julio 8th, 2013

This is a donation of a friend as its not working. Actually this kindle 3 stop working when booting, hence the reason that shows the booting load bar.

broken Kindle 3 Front

broken Kindle 3 Front

I tried to search for onboard blown fuses but every single fuse I found was in good condition. After that I researched over internet and found that has a debug serial port. I tried to attach my usb to serial ttl converter with a little level shifter (kindle serial port works in 1.8v) but had no luck, not even a single character was shown in my Zterm :(

broken Kindle 3 Back Opened

broken Kindle 3 Back Opened

I wanted to install debian to see how the display could work and some few hack I’m thinking of but being the board pretty much dead (only seems to work for its battery charging) I decided to save it for parts as battery, case, metal frame, keyboard and display seems in good working conditions (although I’ve not been able to test them properly). If some generous reader has a kindle 3 with a broken display and he/she is willing to donate it to science I’ll be more than happy to pay the shipping.

LiPo Batteries Hacking and refurbishing

Domingo, Junio 30th, 2013

One of the difficult parts when prototyping is to find reliable power sources. Today is still hard to find the battery size we want to use because country exporting frontiers stops these chemical packages. Here I’ll show how to refurbish dead batteries by combining cells and protection circuits to preserve battery life.

An (almost) dead Apple MacBook Pro (17″) battery fell in my hands so I decided to tear it down to see if there was something profitable. Inside I found that the battery pack was composed with 6 individual cells, paired in 3 groups.

Apple Mac Book Pro 17" Battery Disassembly

Apple Mac Book Pro 17" Battery Disassembly

Seems that the third group had a small voltage difference between cells so they began discharge between them. This leaded both cells to die, condemning the entire battery pack.

Here can be seen the individual cells:

Batteries separated from the main board.

Batteries separated from the main board.

As can be seen the cells doesn’t have individual protection circuits witch are important to avoid discharge below 2.7v to preserve battery life.

I also came across with a small photo-frame that I bough just for hacking fun as is really a bad piece with almost no memory, no SD card expansion, 128×128 display and bad electronics. It cost me 1.99€ and the battery was drain dead from the first moment I opened the package.

Small and dead LiPo battery with the protection circuit.

Small and dead LiPo battery with the protection circuit.

It was inflated and reading 0.26v. Obviously battery couldn’t be rescued, but I salvaged the power cutting circuit. Here is the reverse side of the protection circuit board. Notice the polarity when soldering the LiPo cell and wires:

LiPo Battery protection circuit downside.

LiPo Battery protection circuit downside.

Once I soldered the protection circuit board to the Apple battery cell I ran some charging and discharging tests to ensure the assembly works fine and that power is cut at 2.7v:

Working Refurbished Battery

Working Refurbished Battery

Arduino Sensor Board plus PongClock

Sábado, Junio 15th, 2013

This tiny sensor board was solely designed by Mike Rankin, a friend that help me to bring life to a real custom GPS board. This time he was looking for a multi purpose board to develop anything.

Sensor Board Main display Side Showing Ponglock

Sensor Board Main display Side Showing Ponglock

Feature list:

  • I2C Bus to save pins for future use.
  • 128×64 OLED I2C Display: let’s draw anything
  • Momentary switch on left and cross plus center buttons on right (total 6 input buttons)
  • Arduino Leonardo based: USB for anything.
  • Temperature sensor (I2C)
  • Barometer sensor (I2C)
  • Accelerometer sensor (I2C)
  • Real Time Clock (I2C) plus backup battery.
  • Switched power supply.
  • LiPo charger.
  • Tiny design: let’s make portable projects.
Sensor Board Main Component Side

Sensor Board Main Component Side

I couldn’t resist temptation.. I ported the pongclock code from Rob Parrett to this tiny board. Here is the result:

Hardware is open hardware, you can obtain anything on Mike’s web or you can buy it directly from Tindie. Custom pongclock code can be downloaded from here.

Update: I fixed 3 bugs in the original code to fix pong game behavior to be as accurate as possible, like the scoreboard, ball missing and properly change of hours.