Operating the SPEEDBOX
Powering up and Initialising the SPEEDBOX
Once the SPEEDBOX has been installed and connected, as described in the installation instructions, it can be powered up. When it is powered, the SPEEDBOX will automatically commence its initialisation routine. Within a few seconds the unit will begin to produce output data from the accelerometer. Meanwhile, the SPEEDBOX will search for a satellite lock. This may take up to a few minutes, depending on conditions. It is therefore recommended that the SPEEDBOX is powered up at least ten minutes before use, to ensure that the initialisation process is completed before any testing commences. This also ensures that the analogue outputs and the accelerometers will be closer to full operating temperature before testing commences; the largest temperature related variations in output occur in the first 5 – 10 minutes or so following a cold start.
As the SPEEDBOX starts up and initialises, various status LEDs on the front panel of the unit will light or flash to indicate the state of the unit. The meaning of the status LEDs is described here.
For the SPEEDBOX INS system, the system will only start to output inertial data after the system has converged. This involves driving around at speeds over 30km/h for 1-2 minutes to allow the system to align the inertial data with the GPS data. The progress of this can be seen on a DASH4PRO or attached PC by looking at the Convergence Counter message. The system will start to output data when this reaches a value of 100.
Taking Measurements with the SPEEDBOX
When normal operation is established, the SPEEDBOX will by default provide continuous data over all of the output channels (some outputs can be configured to only start outputting in response to an external trigger, as described in the next section). It is ready to commence testing. The outputs from the SPEEDBOX are designed to be logged by a PC or data logger. They can also be connected to a Race Technology dashboard if a real time in-vehicle display is required. Alternatively, the Race Technology Lite Monitor software can be used to view the output data in real time, via a serial connection to a laptop or PC, or the Performance Monitor software can be used to interactively run scripted tests.
Details of the available SPEEDBOX output formats can be found in the SPEEDBOX reference manual, and in this section of the online knowledgebase
Details on how to connect the SPEEDBOX to a Race Technology data logger can be found in this section of the online knowledgebase.
Details on using the Performance Monitor software to run interactive tests can be found here.
Synchronising External Events with SPEEDBOX Measurements
One common requirement during testing is for events external to the SPEEDBOX, such as pressing a pedal, or passing a certain point, to be accurately synchronised with the measurements made by the SPEEDBOX. In order to do this, it is possible to connect external triggers to the SPEEDBOX, that can be used to switch the low latency outputs of the SPEEDBOX, and/or timestamp the events relative to GPS time so that the events can be later reconciled to the SPEEDBOX measurements.
There are two trigger inputs on the SPEEDBOX. Trigger 1 is on a BNC connector. Trigger 2 is on pin 9 on the expansion port. Both triggers can be configured independently. (NOTE: Only trigger 1 can be used on the SPEEDBOX-INS, since the expansion port is used to connect the external IMU assembly).
Each trigger can be configured to generate CAN and/or RS232 timestamps. These timestamp messages contain the ID of the originating trigger, the type of trigger (rising or falling edge), and the GPS time of week of the trigger, to a resolution of microseconds.
When either one or both triggers are enabled in the configuration, the global trigger state is evaluated based on the trigger parameters and the most recent trigger event detected. The blue LED is lit when the global trigger state is “active” and switched off when the global trigger state is “inactive”. When the global trigger state becomes active the triggered distance output resets to zero and commences recording the distance travelled whilst the trigger state remains active. When the global trigger state becomes inactive the distance is held at the final value attained whilst active. If either of the low-latency outputs (pulse and/or analog) are configured to output in response to the trigger, then they will output whilst the trigger state is active, and cease when the trigger state is inactive. Please see the configuration software instructions for details on how to configure the triggers.
Further details on the triggered measurements is available here
An example is given below:
The user is performing a brake test, and only wants analogue and pulse output to start from the moment that the pedal is pressed, until the vehicle reaches a halt. It is also required to record this distance over CAN. The pedal sensor is open-circuit until the pedal is pressed, and is then closed circuit whilst the pedal is depressed.
With the pedal sensor attached to the BNC input, the output needs to be configured to activate on a low level, so that when the pedal is pressed and the circuit is closed, the output is activated. It is important during the test that the brake pedal remains pressed for the duration of the test. If the pedal is released during the test the output will be disabled.
In order for the test distance to be recorded over the CAN bus, it would be necessary to enable the RT_SB_Cumulative_Distance_2 message using the configuration software. This distance value output by this message would be reset to zero when the pedal press started the active test, and would be held at the final distance when the pedal release ended the active test.