My wife and I have been retired 13 years and spend at least 2 months a year traveling, mostly road trips in our 2014 Chevrolet Impala, 105 trips so far, three trans-continental. |
In addition to photos, we take a Q*Starz recording GPS and a Davis Instruments CarChip.
We usually also take the Picaxe altimeter I made in 2008, which has proved reliable. I upgraded this in 2015 to a 14M2, enabling it to use the 6-segment pressure to altitude code from this project.
This project performs recording of temperature, humidity, altitude and supply voltage.
It is housed in n oak box 8x5.5x4 in, and runs on vehicle 12V. The temperature and humidity probes plug in.
It has three sensors:
1. A DS18B20 digital temperature IC on a probe, using a Dallas 18B20 digital temperature sensor.
2. A AM2301 digital humidity and temperature sensor.
3. A MPX-5100A analog pressure sensor MEMS, from Digi-Key.
There are 2 interior metal sub-assemblies, front and rear, inter-connected by a 15-pin ribbon cable.
The front assembly contains:
1. A 12-position rotary switch for display selection, and a 16-segment voltage divider on a board.
2. A Ledtech UN(M)5624 4-digit 7-segment green LED display and a MC14489 driver/multiplexer on a second board.
3. A RogueRobotics uMMC Secure Digital (full-size) to serial interface and on-off switch.
The rear assembly contains:
1. A board containing a power regulator and 5-to-1 voltage divider to monitor the supply voltage. This was upgraded in 2015 to prevent memory file system corruption from sudden power loss.
2. A board containing the Picaxe 18M2 and a DS1302 clock-calendar with a CR2032 backup battery.
3. A board with the MPX-5100, its amplifier, and the AM2301 PWM to DS1302 interfacing circuit.
4. A 3-way momentary toggle switch for adjustments
The Picaxe program has an initial one-time initialization section and a main loop, plus sub-routines.
This project had great complexities both for the circuit and the software.
For convenience when traveling, the logger output is transmitted to a hand-held display.
|Here are photographs|
Here are the circuit diagrams
|Here is the code|
|Here is the description of the hand-held display|