Alerts

Overview of the Alert Setup

The main reason that we installed a monitoring system, was to allow us to observe and understand the state of our adventure truck through the signals it generates. However, we also would like to be alerted to problems, or conditions that could become a problem if not addressed. Molly’s alert system is a bit like a check engine light, in that it indicates a problem. It could be something more serious like a low tire pressure or freezing water tanks, or less serious like flat batteries or low water tank levels.

The monitoring system is configured with two levels or severities of alerts. Warnings indicate an alert condition that should be investigated, but does not require immediate attention. Alarms on the other hand, indicate a condition which needs to be investigated immediately. Some warnings if not addressed, will turn into alarms.

As an example, if the the pressure in a tire falls below a certain level, this is indicate with a warning. If the pressure continues to drain, it will ultimate trigger the alarm.

We have a series of dashboards that present the status of Molly, including any alarm conditions. Warnings are indicated on these dashboards in orange, while alarms are indicated in red. Any red alarms also sound the buzzer. Once the alarm is sounded, we can go to the dashboards and find out what is wrong.

To ensure the buzzer does not startle the driver while driving, it will initially only “chirp”. The chirp is implemented by turning the buzzer on for only half a second. If no action is taken after 5 chirps, where each chirp is 90 seconds apart, then the monitoring system will activate a continuous buzzer.

The buzzer can be silenced at any time. To prevent the silence feature being accidentally left on, it is reset each day at 9pm. The logic to silence an alert area is independent from other alerts. For example, silencing the alarm for the TPMS will not silence the alarm for House Battery. This is to ensure multiple alarms are not missed.

The Buzzer

Initially the buzzer was created to alert us to a problem with the Tires. Our Tire Pressure Monitoring System (TPMS) is great, but the model we choose was really intended for remote vehicle monitoring, and has no head unit for the driver. So, we added some electronics to create the buzzer. Over time we discovered more uses for this buzzer.

The buzzer is controlled by a Node MCU, which is a low cost (around $3) open source IoT platform, It is based around the ESP8266 microcontroller with wifi and other useful features. In short, it allows us to connect and control things. We have connected a single channel opto-isolated relay which can be controlled by a 3.3 volt digital output signal from the NodeMCU. Finally the controller is powered by a small 15 watt power supply.

The buzzer is a 100 decibel (at 1 meter) reversing horn which operates on voltages between 10 and 24 volts. The current draw is less than 0.6 amps and emits at a frequency of 2800 Hz +/- 10%.

The system is wired up as shown the diagram below.

Click image to enlarge

The buzzer is hidden away behind the console in the front of the cab. It might be out-of-sight, but it can be heard from the entire truck. It is more than loud enough to wake us up while sleeping and is about as loud as a smoke alarm.

Sounding of the buzzer is mainly controlled by the node-red based monitoring system. When the monitoring system detects a problem, it will send a message over wifi to the NodeMCU, which will sound the alarm. As a self monitoring check, the NodeMCU also includes a watchdog. If no message is received for more than 10 minutes, then the buzzer will chirp to indicate a failure in the system.

The buzzer will chirp every time the engine is started, this is to check the buzzer is working before we drive off.

What Alerts Areas are Configured

Alerts are configured for the following areas. This list is growing each time I find time to write more software to add more alerts.

Tire Pressure

Each tire has a pressure sensor and each sensor is configured with a nominal tire pressure setting. Using this nominal pressure setting, each sensor can independently raise an alarm where the tire pressure deviates from this nominal setting by more than or less than 25%. The sensor itself will raise an alarm, which in-turn triggers Molly’s alert system sounding the buzzer. The in-built alarms in each sensor is the primary way to alert us to issues(1).

To enhance what is offered by the sensors, we have configured more alert conditions that a single sensor can’t individually detect and alert on, but a set of sensors when compared with each other can:

  • Pressure in a tire exceeds or falls short of the other tires by more than 5 psi is a warning, and by more than 10 psi is an instantaneous alarm.
  • Cross axle differential pressure is more than 10 psi is a warning, and is more than 15 psi is an instantaneous alarm.
  • Temperature in a tire exceeds or falls short of the other tires by more than 20ºC is a warning, and by more than 30ºC is an instantaneous alarm.
  • Communication has been lost with the TPMS system for greater than 90 seconds is a warning and greater than 10 minutes is an alarm. Communication is also deemed to be lost even when messages are being received but where these are failing their checksum and therefore maybe invalid.
Environment

We always worry about freezing conditions and protecting the outside water tanks. The following alarms have been configured

  • Outside temperature is below zero for more than 30 minutes and the tank heaters are not on for tanks with water in them.
  • Inside temperature is below freezing for more than 30 minutes.
Battery Condition

The house batteries are monitored by a smart shunt, which is able to keep an eye on our batteries with its own alarm logic. This includes alarms for low state of charge, low or high battery voltages and low or high temperature readings. These alarm will activate when the value reaches a set threshold and will deactivate once when the value clears this threshold. If the smart shunt triggers an alarm, then this immediately triggers Molly’s alarm. In addition to these alarms, we have also configured the following extra warnings and alarms:

  • Warning when the State of Charge is below 20%, which represents about 1 day of useful charge remaining. The smart shunt alarm is set at 10% State of Charge.
  • Warning when the battery voltage exceeds 14.4 volts, which is higher than what the any of power sources should generate. The smart shunt alarm is set at 14.6 volts. The BMS will automatically disconnect if the voltage exceeds 15 volts (+/- 0.12 volts).
  • Warning when the battery voltage drops below 12.5 volts. This value is based on voltage vs percentage charge remaining charts provided by the battery manufacture. The smart shunt alarm is set at 12.0 volts. The BMS will automatically disconnect if the voltage is below 10.2 volts (+/- 0.2 volts).
  • Warning when battery temperature is below 15ºC for more than 4 hours, which is lower limit of the optimal battery temperature. The smart shunt alarm is set at -15ºC. The battery BMS low temperature protection operates at -20ºC.
  • Warning when battery temperature exceeds 35ºC which is the upper limit of optimal battery temperature. The smart shunt alarm is set at 55ºC, which is the maximum operating temperature. The battery BMS high temperature protection operates at 65ºC.
  • Communication has been lost with the smart shunt for greater than 30 seconds is a warning and greater than 10 minutes is an alarm. Communication is also deemed to be lost even when messages are being received but where these are failing their checksum and therefore maybe invalid.
ECU

The truck has it’s own alarm system and will turn on the check engine light (or malfunction indicator lamp) and has its own buzzer which it can also activate. Check engine light is considered a warning. The FUSO truck can indicate other faults on the dashboard, and not all of these fault conditions are visible to Molly’s monitoring system. So the FUSO dashboard is the primary location alerts are presented. However, the following warnings have also been configured.

  • Trip Odometer has changed by more than 5 miles between readings, which is implausible.
  • Communication has been lost with the ECU for greater than 90 seconds. Communication is also deemed to be lost even when messages are being received but where these are failing their checksum and therefore maybe invalid.
Water

To be written.

Note (1): It is not clear if the Tire Pressure Pro sensors will alert on high (or low) tire temperature.