While being away doing other things, I was thinking about ways of improving the overall design. I decided that the main problem with the project was that it consumed too much power while in sleep mode. After all, it is intended to be in a truck that may be parked for a long time. So I designed a common power board for the CPU and the gauge, and redesigned the CPU and gauge to use more modern, low-quiescent regulators. Car power can be pretty spikey and dirty, so I made a filtering board that will also kill transients and noise in general. The output is an 8 volt bus that supplies the gauge and the CPU
The CPU itself received an upgrade. The main item was the MRF24EG0 WiFi module, which replaces the ‘b only’ module. In software, the IP stack got upgraded to the latest version to support the new module. In addition, the afore mentioned voltage regulator upgrade and a 5v software switch brought the sleep current down into single digit mA figures.
The most important redesign was probably to combine the geiger circuitry with the GPS, greating a sensor board with a minimum of cables.On the top side, you see the RYN25AI GPS module and the 400v high voltage module for the geiger counter. On the bottom side, you see the two SBM-20 geiger tubes. An additional feature of the new board is that it holds a RS232 level converter and an header (left in picture) that is pin compatible with the Iridium satellite 9601 SBD modem. I picked one up at a surplus sale, but haven’t decided whether to use it or not. Anyway, the hardware is there, just in case.
This is the CPU chassis, holding the CPU board and the power board. The display and buttons are for debugging – I may make another version without the display to be installed in an actual vehicle.
Here is a picture of the whole set-up, hooked up and working. Still doing some final wiring, so the back wall of the CPU enclosure is off. I found some neat military-style multi-pin plugs on ebay that came in handy for hooking up the cabling. It looks cool, but I still think they’re a bit flimsy to be real MIL-SPEC. Or, maybe, some military outfit will get in trouble when it rains… 🙂
Oh, yes, the relay board: also found on ebay, an 8-channel relay board with optocouples and everything. This enables the set-up to control a vehicle remotely via SMS, APRS, Iridium, Wifi, or BlueTooth. One of the relays is used to switch off the APRS radio when the unit is in sleep mode. The others can be used for door locks, horn, ignition cut-off, or whatever. I find that there’s a lot of good stuff listed under ‘Arduino’ when you search ebay. This board has of course nothing to do with that specific platform, it’s just in fashion right now…
So, what does it look like when you put this in your survivalist vehicle?
This is the geiger display, showing the ‘counts-per-minute’. The common bar graphs indicate the GPS coverage (satellites used/available), the GSM signal strength, the number of WiFi activity in the area, and the radiation level. Using a button, you can change which screen to display. If any parameters go outside the preset values, the screen will switch automatically and an alarm screen will be shown. These are the most important screens – there are many others.
This display gives us the raw GPS data, speed, disrection and elevation. Nothing is showing for the bearing since the speed is too low to give that reliably (5 km/h minimum)
There’s the WiFi hotspot list, giving the strongest access points seen…
One of my favourites – the APRS station radar view. This shows the bearing and distance to nearby APRS stations. It autoscales, so that you always see stations if there are any. This was probably the most tricky thing to make on the PIC32, requiring some pretty heavy floating point math on the CPU.
The APRS data screen is useful – it cycles through the data from all seen APRS stations. displaying data and the the relative position for each one.
And, finally, the mandatory reference to ‘the Matrix’ (yes, it moves) Useful? You decide!