I have been under the weather this week, which is unusual for me.

It is just so much fun trying to build electronics when you are feverish, nauseous, dizzy and coughing up a lung. None-the-less, the show must go on. The first thing I need to mention is the last item in the sponsored kit has arrived. (although I won't need it for this project)


No video this week - my throat is too sore and I'm too hoarse and I'm coughing too much.

I finally received enough parts to build my sensor booster pack - here is what it looks like assembled:


The black module on the left is the CO2 sensor, at the bottom is the UV sensor, the orange sensor is an MQ3 (alcohol), the red sensor is an MQ7 (carbon monoxide), and the stainless sensor is an MQ135 (air quality). The 3 sensors at the right are in sockets, allowing any MQ sensor to be substituted. The pots allow me to adjust offset and gain of each signal to get the best range out of the A/D. Not visible in this picture are 3 LEDs, one opposite each sensor - between the sensor and the pots. These allow me to see when each heater is on.

You can see I got to use nice big traces and spread out the signal conditioning circuitry because the card had to be large enough to get all the sensors exposed to the air and it left lots of room in the middle under the display.

Here is what it looks like when all booster packs are stacked up into the full module:


The packaging will allow all sensors to access ambient air.

I would normally like to show the card working, but I think I will wait until my head clears before trying the smoke test (power-up).


While I'm feeling miserable, I might as well point out some background and mistakes with the project.

I have built RF power monitoring circuits in the past to work in the Bluetooth/WiFi/Zigbee frequency band (2.5GHz). The actual modules I built are being used at another location but I still have a couple of bare cards. They have an RF power monitoring and signal conditioning section, an SPI A/D, and an FTDI SPI-USB interface. There is no MCU - the A/D is controlled by a program on a PC via USB. One card has a directional quad antenna on it.


Comparing these old prototypes to the new booster pack you can see how much my prototype cards have improved since I started getting them made off-shore.

I came close to designing a version of this power level meter that would work in a booster pack, but I decided to order a ready-built module on-line.

Unfortunately the module I ended up ordering only goes up to 500 MHz - as I discovered when I powered it up ......


The versions that go up to 3 or 8 GHz look the same - I just messed up the order. The delivery schedule on these precludes ordering another one. As you can imagine - I was pretty fed up with myself. I was going to make a wrist mount for the module, and possibly interface it to the TI MCU but alas it won't end up in this project.

I ended up buying another great little meter to take readings but totally blew my budget in the process.

Anyway - enough griping - there has been progress despite the woes.

I'm still waiting for a few parts, but none are show-stoppers, I can complete the hardware with what I have.

So now I just need to get well, get my act together, make it work and spend the time to finish.


All links to blogs related to this project can be found in the first blog here:

Safe and Sound - Invisible Hazardous Environmental Factors Monitoring System - blog 1