Step 1, POR: Risk Mitigation
8.5 Risk Assessment
draw of each LED and how you could supply potentially 400 mA or even 1000 mA of current to the LEDs. The typical total current you can source from a microcontroller is less than 200 mA.
8.4 Preliminary BOM: Critical Components
Sketch the functional diagram as much as you can, even as just a block diagram. This will help you think through the power flow and the signal and information flow. The better you can conceptualize what each circuit block does, the better you can decide if the design will meet your needs.
Based on the block diagram, sketch the schematic, even if just on the back of a napkin (metaphorically). It is not critical to have all the details, but at least the major components and their connections of signal and power flow.
Identify the most important parts you will need. Find them on digikey.com or whichever source you will use to purchase them. To make purchasing and tracking orders easier, and less risky, try to find all of your parts from the same distributor, like
www.digikey.com.
Check delivery time for every critical part. If the lead time is 6 weeks, maybe find another vendor or consider a different part.
Find the datasheets, and explore their features and any specific requirements — software, drivers, etc. Read the datasheets to learn the correct way of using the components and what performance you can anticipate.
8.5 Risk Assessment
In this first phase of the project, we look at risk assessment and risk mitigation. The combination of these two is risk management.
This is as big a part of the design process as is the actual design.
There are many more ways of screwing up a board and getting it wrong than doing it right.
You should get in the habit of thinking about the design process like Ralphie’s mom, rather than like a Colorado Bro. Get in the habit of thinking of all the worst-case scenarios — everything that could possibly go wrong, before it happens.
The first step in risk management is identifying all the potential problems. Step back and ask yourself, what are all the possible things I can think of that could go wrong?
If you are assembling your board yourself, do you really want to use 0402 parts? You may think it is an act of macho heroism (“here, hold my beer”) but in reality, it is a huge risk site. Why not avoid this risk site and use 1206 parts which have a much lower risk of introducing assembly problems? You should have a strong compelling reason to voluntarily take on more risk than absolutely necessary.
Is it possible the footprint for a component in your library is wrong?
Is an enable pin supposed to be pulled HIGH or LOW?
Should an I/O rail be powered by 5 V or 3.3. V?
Should there be a pull-up resistor on the I2C bus?
Are the RX and TX pins connected correctly?
It is hard thinking of worst-case scenarios. This is why you should use every opportunity to practice. Get in the habit of looking for hidden potential failure modes and play out possible plan B, plan C, and plan D contingency strategies.
This is exactly what is done in war gaming exercises. It is about playing out possible scenarios of, “if the enemy does this, we will do this, and the reaction will be that, so we need to be ready with this.”
Risk management in product design is a lot like playing chess. You need to think as many moves ahead as you can. As your opponent makes a move slightly different than what you anticipated, you
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adjust your strategy. Your opponent in product design is the real world.
While we might think we are wonderful designers and builders, and every project we work on will be designed and
executed perfectly to work the first time, few of us in practice can attain these heroic levels of perfection.
We all make mistakes. No matter how hard we try, we will continue to make mistakes. What we can hope for is to make fewer mistakes in the next design. The better we can anticipate a problem, the better we will be able to implement a plan to not encounter this problem in the current design.
Risk management is a two-step process:
1. Do a risk assessment to identify all the possible things that could go wrong.
2. Develop a risk mitigation plan to design these potential problems out of the product and its implementation or a Plan B, C, D, or E in case a potential problem does arise.
A valuable exercise at the very beginning of every project is to sit down and make a list of all the possible problems you can think of that could arise. This is where thinking like Ralphie’s mom is such a valuable skill.
Then, you can access how likely each risk is: likely, possible, unlikely, black swan (very rare event, requiring multiple simultaneous
factors, like the perfect storm or a rogue wave), or never.
If you are called a worry wart for raising your concerns, wear it with a badge of honor, that you are doing exactly
what you are supposed to do. But also try to offer a risk mitigation solution for each concern.