System Integration

May 20, 2024

Challenge

• Individual assignment:

  Design and document the system integration for your final project.😰

Weird assignment this week but the Session was really great Neil introduced a lot of things my mind has thought differently about them but now I have more insight about some of them and ways to solve’em {I hope so🫤}.

Let’s Start

My final Project Is about a small device can be placed in any room or office with good looking (As decoration) with the ability to monitor the surrounding environment (CO2, TVOC, PM2.5, Humidity and Temperature) levels ans send them to IOT platform to be accessed from all over the world.

• The Project seems to be fine when first I thought about as it just some sort of sensors together feeding data to a Microcontroller then pushed through to an IOT platform with some kind of output RGB’s attached with the device to give it a great looking and wood finished housing with a stand (PLA or Wood).

• Very nice Looking when I finished the design {I thought 🤥}.

• But step by step I started ordering my sensors and then testing them all together.

• At this moment everything is becoming clear more and more.

• My first struggle was {WOW sensors are not always small 🤣} –> When I saw the PM Sensor (I thought It might be slim at least) but it appears big a bit and it wont fit inside my lovely small package.

As seen from the datasheet the sensor is 50 mm width and 38 height in addition to 21~ mm in thickness ( Which what I was thinking my device might be).

Lesson learned read the datasheet before you make your purchase in addition to that a deep research is required always (I have to look to the other constrains not just the goal I want to reach).

• Now to come over this issue I decided to have this Sensor outside my device and I want to attach it in the stand and then wire it with the device.

• This was what I have in my mind but later I understand that this sensor will need a good ventilation and my device won’t be and also this might affect the other sensors specially (CO2) sensor –> As it doesn’t require air flow (air flow might happen due to the fan attached with the PM sensor).

I had different thought where I can connect it with another microcontroller but it might be extra complexity because I want to add also power to this MCU.

First Issue resolved –> (I hope So)

Then I had to think about the other sensor requirement like the (CO2) sensor.

• This sensor have double chamber to take readings and also for auto calibration so this sensor needs time between readings for an accurate read.

–> This might be affected by the PM sensor and I have resolved it by moving this sensor out.

• Then this sensor will require no direct sun light so I decided to flip all the PCB to face the bottom of the device and add some ventilation holes in the sides and back of device ( But I need to figure a way to have these holes without ruin it’s look).

This sensor works using Infrared light to detect the amount of CO2 particles in the air so any direct sun light will affect the readings for sure.

• I care the most about this sensor (As my device is all about CO2 mostly).

All the sensors do not require a direct air flow so fans might have a bad effect on the results so I need to take ventilation holes diameter into deep consideration, –> SO for me I need to have a good air exchange but not as fast as a second.

• So my design already resolved this Issue by having front ventilation holes and I might need some in the back.

Then I need to consider the size of the Device–> As decided before I want it to be maximum 10 cm in diameter and I need around 3 to 4 cm thickness.

• This will require me to have the minimum number of wires inside and for this I decided to have my PCB designed again and I made sure to Include all the sensors and the component mounted on it with a maximum diameter of 80 mm.

• I was thinking of adding a battery in the device (As the XIAO ESP32C3 has a charging circuit ready for such system) but this might have my device thickness to increase so I decided to include the design and all the needed in the PCB Fabrication but with a 50 % chance of not having it in as the battery is a bit big to include.

Then I want to consider the closing of the housing and how I want to fasten it together as I’m Looking for Top part and Bottom Part then I want them to be fasten with each other.

• The first thing came to my mind was having it glued together and my mind was so relaxed with this Idea until {Neil said : Worst is adhesive because you can’t Undo an Adhesive easily} –> My mind start to spark like an engine lost its coolant hose, Until Neil continued saying {Better is fasteners but it require a lot of labor to fasteners in and out ….. until he finished.}.

• This was like a mind failure but “Alhamdollelah I was focusing that moment and heard that from Neil”.

• I thought about it very carefully later on and I wanted to use snaps together but this will require me a careful alignment so at this moment I needed a break and went out with a friend to release a bit of stress and finding an easy solution for me.

• Alhamdollelah he came with a very simple solution (Magnets) 😲. –> Solved 🥳

• My design Is circular and I can have the magnets where ever I want and they will snap like a boss together.

• Neodymium magnets are strong and small a I can fit them in my design.

link

Conclusion

In general my most issues for integration rally on the design and the size of the device some of them are sensor requirement such as the PM sensor and the CO2 sensor, But I loved this session as it gave me a shock to rethink deeply in some of the issues and also it pointed some of the the easy things (My mind thought) to solve but it appears to need some careful consideration.