Note; Missing images are Google image server issue, hopefully they will restore the service soon.
This module is used in our Greenpower Race Car
and forms part of the instrumentation and telemetry system used to monitor the vehicles performance.
It is used with a number of accompanying modules to provide a fault tolerant, low cost vehicle network system that can provide diagnostic and telemetry about the vehicle for post race analysis and live data reporting.
The principle is to make the system accessible to school children by demonstrating the ease with which such systems can be constituted using tools readily available to school children. The system is designed to be modular to allow phased development and fault tolerant to aid problem solving and investigation.
One of the main problem with any automotive electronics system is keeping moisture at bay. The housing is designed to seal the electronics module from water spray from the wheels, and intense rain (2016 race final at Rockingham
11:00 was torrential for around 45 minutes).
The module shown houses the SSR (Solid State Relay) unit that was used to switch fans in the vehicle on and off. These fans can have multiple purposes not just cooling! Obviously the module can house any desired electronic and interface to other devices such as temperature sensors, an RPM sensor or current sensor as desired.
The unit is designed to use 3D printed sealing components. If 3D printed components are not available then moulds can be created from the included STEP model files on Thingiverse to allow the same functionality to be achieved. We also had success with liberal use of Silicone sealant with prototypes, though it's somewhat messy as most potting processes tend to be.
The principle purpose of the system is to protect the DC motor from overheating due to excessive motor load arising from incorrect gear selection. As the motor is one of the single most expensive components on the vehicle, it's worth some effort to protect it. A side effect is the batteries tend to be protected as well. As they are more likely to last the race when motor state is understood and overheating managed with correct gearing. We advise and use ourselves thermal indication stickers
as a backup.
|Greenpower Race Telemetry System Configuration|
Data can either be polled by the Raspberry Pi or requested. The latter is typically more responsive though of course requires a request, response sequence with time-out. So is a little more complex in software. Data is held in the telemetry unit and written to the SD card principally as a back up in text file CSV format compatible with Excel for direct import at the end of each race or days racing.
Script running on the Raspberry Pi is relatively straightforward PHP
which access XBee radio transmission stage via the RASPI serial port. The PHP script then updates session system variables which can be pulled by multiple clients and if required downloaded straight into Excel live from the vehicle. The PHP scripts handle all client requests and ensures efficient data request to keep power usage on the vehicle to a minimum. Finally a PHP script makes updates via JSON
(see image at bottom of page). With a separate lightweight presentation script allowing customised 'mobile' experience. The idea of this is to attempt to engage other than engineers i.e. graphic design talent, logistics, management and software engineering. Note no special tools or 'tricks' were used, the whole of the graphics design for this system were performed done in Microsoft PowerPoint. PNG files are then used as images for various elements. The scripts of course could readily be re-written in any language and this approach is intentional to allow such flexibility
|Greenpower Race Telemetry Page Showing Live Vehicle Data|
The digital displays were constructed from an open source
font http://www.keshikan.net/. Select the English version if your Japanese is limited.
Using a slightly modified USB Wifi key to allow for remote antenna connection. A local Wifi hot spot allows simultaneous access by multiple clients. This is also particularly useful as the pit team is often not in the best spot for radio reception from the vehicle. The configuration allowed really flexible site arrangements. Using 2D bar codes that could be scanned, configuration on mobiles phones is automatic and only requires scanning of the 2D code to enable access to the race portal. This portal also has significant documentation available to support the vehicle. The number or race teams on site and other users having Wifi in the vicinity was significant. With one user electing to set up a transmitter to a remote location through our mast! with around a meter clearance to our vehicle telemetry downlink! We might have had half a chance with as little as a few of meters separation. Can't believe it helped his radiation pattern and we had been in exactly the same spot for two days by this point! We managed, though it could have been easier for all concerned.
|Desensitisation of telemetry downlink front end from co located high power Yagi transmission! |
Given the rain during 2016 finals days this really paid off allowing the monitoring pit crew team to remain in touch and dry!
|Greenpower Race Telemetry Data Logger Configuration|
|Greenpower Race Telemetry MicroLAN Concepts|
|Greenpower Race MicroLAN Connection System|
|Greenpower Race Car Power Supply For Telemetry Electronics|
|Greenpower Electronics Housing - With Sealing And Vibration Dampers|
|Greenpower Electronics Housing - See Through Image|
|Greenpower Electronics Housing - Internal View|
|Raspberry Pi Telemetry Down Link And Race Hot Spot|
The Raspberry Pi runs NOOBS, with the addition of:
PHP (with Memcached)
These are all standard distributions on the Raspberry Pi
Web files are placed in the relevant /var/www/html sub directory with appropriate permissions.
|Electronics Module Housing Single Outlet Drawing|
|Raspberry Pi Web Based Telemetry Monitoring App (Basic)|
|Greenpower Raspberry Pi Web Based Telemetry Monitoring App (2016 Season)|