Week 13

This week, we continued making our electrical circuit to show for our project. We figured out how the drive by wire system works. Shown in the below diagram is a wiring diagram for a Subaru Drive By Wire throttle system.

Next we decided on our processing and decided to not use a 555 timer chip changing our mind because we weren't actually going to build a prototype and instead going to make an electrical circuit to prove how our system worked as lacking time. We decided to use logic gates to process our signals.
The following image shows the logic table.

This table indicates that if the SOS (Seat Occupancy Sensor) detects pressure on the seat, and the vehicle speed is over 20 kph and the seat belt sensor doesn't detect a seat belt buckle clipped in, the throttle output will turn their respective signals high and low.

We found that the waveform with the throttle cut looks like such.

The red line is the high signal and the blue line is the low signal. As you can see in the image, the idle is at 0.7V low (blue) and 4.3V high (red). At just before 0.6s, the throttle is opened and the signal begins to invert as shown in the previous TPS waveform however, in this waveform, you can see the signal being cut as soon as the vehicle speed sensor senses that the speed is over 19kph and the SOS (Seat Occupancy Sensor) and the SBS (Seat Belt Sensor) are both also on.

We're expecting to be completed by mid week next week. 

Week 11 and 12

Weeks 11 and 12 we basically just tried to research on how to connect our throttle cut off system to an existing drive by wire throttle system car and where we will connect it on the circuit diagram. We met Simon a few times to try and figure out how we will achieve what we want and are still stuck on making the circuit. Once we make the circuit on paper, if we have enough time we will make the circuit on multisim and try and simulate our combined system of Warning Light, Buzzer and Throttle Cut off.

However I feel that we should be able to find out whether we will be able make a simulation on multisim in the deadline or not. We decided not to use picaxe chip as it requires a lot of programming and instead are going to try and connect the system using logic gates which are already programmed into a 555 timer chip. We feel that it will be a bit easier to do that and we 'should' be able to achieve the same results without having to learn programming in a small amount of time.

Week 10

Week 10 was our stage 2 demonstration which I considered to be the hardest one yet.
Our Three outputs as previously stated were
1) Seat Belt warning light - Seat Belt warning light must blink for 6 seconds from Ignition with 0.6 second frequency, with a 50% duty and a chime bell. If the IG. is turned off within 6 seconds, the warning light and chime bell must be 'off'. Below is the Seat belt warning light control circuit.

2) Buzzer System - If Seat Belt has not been fastened “After 15 second of ignition on status”. The buzzer will play the audio 3 times along with LED. If the seat belt is still not fastened, the audio and LED will flash after every 20 seconds.

3) Drive By Wire Throttle - Drive by wire throttle has no mechanical linkages, it saves weight, is more accurate and has better response times however the cost to make it is higher than a regular cable throttle. How it works is the driver presses gas pedal, there is a sensor attached to the pedal which measures how much it is pressed which then sends signal to ECU to turn the motor accordingly which in turn opens or closes the butterfly valve to allow for air to come in. There is another sensor after that which sends signal back to ECU to measure how much the butterfly valve is open or closed to ensure everything is working as it should. 
Below is an image of a gas pedal from a drive by wire throttle system with a accelerator position sensor.

Week 9

Coming back from two week mid-semester break, we decided to meet up on Monday and share with each other what we had done so far in the holidays and share all the research we had done to start preparing for stage 2 demonstration.

We knew what outputs we wanted which were:-

1) Buzzer 

2) warning light 

3) Throttle cut off over 20 kph when seat belt is not on (see last week's blog for logic table for desired results). 

We decided we were going to use Drive By Wire throttle system to cut off the throttle which will all be explained in next week's demonstration. 

Week 8

We did not have any class during Week 8 and the following two weeks as week 8 had a good Friday public holiday followed with two weeks mid-semester break. However we basically just revised on what we had done up till now including our initial demonstration, stage one demonstration, Gantt Chart to see where we are on the timeline and read the books we had loaned from Simon to read about our processing and outputs.

We decided to read up on logic gates and made up our own basic logic table as to how the system will react to each different scenario shown below.

So, using this table, we are able to get the results we desire.

Week 7

Week 6 included of a lot of research of our inputs and we decided to finally choose, Seat Occupancy Sensor, Seat Belt Sensor and Vehicle Speed Sensor for our project.

1) Seat Belt Sensor - the seat belt sensor works using a Reed Switch which is triggered when the metal tongue side of the buckle is inserted into the main buckle housing, then the sensor and the magnet on the tongue become magnetically isolated by changing the state of contact. This in turn transports the switching or the sensing function. Where as during the disengagement of the seat belt tongue and the buckle housing, the interference no longer exists and the reed sensor contact returns to the reset mode. A .gif format image is shown below of how it works

2) Vehicle Speed Sensor - A Vehicle Speed Sensor is used in many performance enhancing electronic systems in the car such as ABS, Cruise Control and traction control to name a few. More systems in which this used was explained in our demonstration. They're usually gear driven, found on the transmission case or differential assembly and measures transmission output speed. A Vehicle Speed sensor uses components such as 2 hall effect sensors, a rare earth magnet and appropriate evaluation electronics.

Image shown below.

3) Seat Occupancy Sensor - A Seat occupancy sensor consists of a flexible sensor mat which is inserted into the vehicle seat. The mat consists of two sandwiched carrier sheets held together. An increase in pressure on the mat will cause change in electrical resistance which informs the system whether the seat is occupied or not. The occupancy on the seat is only detected for weights higher than the 40kgs, this depends on manufacturer's specifications.

Week 6

This week was all about research, we had to research our inputs and find out more about them. So we had decided to meet up on Monday which is our day off and do that. We found out how the Seat occupancy sensor, vehicle speed sensor and Seat belt sensor all work electrically.

We decided to put it all together in a presentation to demonstrate next week for our stage 1 demonstration. Nothing more than this happened this week as we had to also do our first assignment for Automotive Professional Practice. However, we did meet with Simon and loaned a few books from him to read for home work.

We also made a Gantt Chart to timeline our progress and schedule so we don't miss our deadline as shown below.