H2 Board - UAlberta-EcoCar/wiki GitHub Wiki

The hydrogen board (H2 Board) on Fuel Cell Controller’s (FCC) main duty is to detect the usage and flow of hydrogen gas used to power the Fuel Cell itself. Should hydrogen be detected outside of the fuel cell, an emergency stop signal is sent to the FCC in order to stop the vehicle. The H2 sensor is based around the Hanwei Electronics MQ-8 Gas sensor and the Atmel ATmega328P TQFP microcontroller (discontinued) in order to create a system in order to detect hydrogen levels and transmit to the main FCC. it has safety precautions built in to help protect the Fuel Cell and detect H2 leaks.

For future usage, it might be possible to create a mobile testing board in order to better facilitate testing during the building stages of the vehicles so that H2 and Fuel Cell testing can be done somewhat independently of the FCC’s installation and wiring. Another usage from this could be testing at various stages of building and also during competition. Having external boards help better prepare the team in the event of damage, malfunctions.

The entire schematic diagram will be discussed in detail. An overall diagram is available here, while sections of the boards will be included in the discussion.

Figure 1: Schematic diagram for hydrogen sensor board v2 (H2 Board)

The first stage is the MQ-8 Hydrogen sensor. It requires 5V to power and will produce a output signal H2OUT at pin 1. This signal is carried in to the microcontroller at pin 27.

Figure 2. MQ-8 hydrogen sensor.

The H2 board utilizes a 6 pin ICP Controller in order to program the board itself and MOSI,MISO and SCK are outputs that connect to the microcontroller at pins 15, 16, and 17 respectively.

Figure 3: ISP Connector.

The Microcontroller is powered by a 3.3V voltage. A Texas Instruments TLV1117-33IDCY is used to drop the 5V voltage that is obtained by an auxiliary battery via the Aux Power Connector.

Figure 4: Voltage Regulator

The Microcontroller is the most important piece of the H2 Board. An Atmel ATmega328P TQFP is used for the microcontroller, it is no longer in production. The microcontroller takes the input signals from the hydrogen detector and outputs a constant signal, H2_OK, to the FCC on the operational levels of H2. It also maintains an emergency stop signal that is sent to the FCC in cases of H2 leaks. Each signal sent to the FCC is duplicated to ensure that there are proper fail safes for the FCC.

The H2OUT signal is received at pin 24. This signal is converted to H2_OK (pin 23) and EXTRA_SIG (pin 24) if the H2OUT signal is within the defined range of acceptable signals. The purpose of H2_OK and EXTRA_SIG is to be a constant signal to the FCC monitoring H2, should at any point the H2OUT signal is deemed unacceptable, H2_OK and EXTRA_SIG will not trigger and the FCC will stop the fuel cell and vehicle.

The emergency stop signals are ESTOP1 (pin 32) and ESTOP2 (pin 1) are used as an override to H2_OK/EXTRA_SIG to force the FCC to stop the fuel cell and the vehicle. This can be caused by a leak being detected by the hydrogen sensor and the H2OUT signal.

Figure 5: Atmel ATmega328P TQFP microcontroller.

The H2 board connects to the FCC via ethernet. A TE 1734723-1 RJ11 jack is used. The two emergency stop signals are delivered two separate, independent devices. H2_OK is mapped to pin 1 while EXTRA_SIG is mapped to pin 2.

Figure 6: Ethernet connector on the FCC along with the emergency stop receivers.