Electronics Design Process

[bonbonbaron]

Hi all,

How does the electronics design process work? Here's my current best guess as to what it entails:

1. Get requirements.
2. Obviously have a schematic of what you want to build. This will have lots of unknown resistor/capacitor/etc. values.
3. Write out the entire system of equations using Kirchoff's Laws.
4. Solve the whole system leaving the resistor/capacitor/etc. values unknown.
5. Now that you have a solution, give each element a value to satisfy it. Good to check the pricing and sizes before doing so.
6. Simulate your model on a computer to validate it before buying all the parts.
7. If the model looks good, buy everything and have at it!

Also, it's hard for me to imagine that every electronics wizard out there does all the above. Most instructional videos have people saying things like, "Oh, well, this transistor should do the trick-- it ain't overkill," or, "For this motor and a 9V battery, you wanna have, oh, I dunno, a resistor that's somewhere around 50 kΩ." Seems like some people have more of a experiential/experimental approach than the rigid and thorough engineering approach I delineated above.

Are you one way or the other? Or is there a way to get the best of both worlds?

Any enlightening is greatly appreciated; this is something I've wondered about for a long time. Thank you!

B3

 

[(*steve*)]

Having a schematic is nowhere near step 2.

and your steps 3 and 4 kinda don't ever happen.

And whilst you might simulate the circuit, you may also build a prototype, or at least try out various components of your circuit.

Here's what I'd say is _a_ process:

1. Determine requirements
2. Create a conceptual solution by breaking the problem into smaller modules.
3. Consider options for the modules, understanding that the choices made for one module will likely affect others.
4. Draw schematics of the various modules.
   
5. Choose suitable components for the modules.
6. Simulation may be useful here
7. Build prototypes of any modules where you need more information.
8. determine suitable packages for components. Consider availability and perhaps options to reduce the number of different parts.
9. Finalize a complete circuit diagram.
   
10. design a PCB
11. Make a sample and test it
12. Refine the design
13. Send to production.

There's still a lot of extra stuff you would do, but this is kinda how I work.

 

[OBW0549]

How does the electronics design process work? Here's my current best guess as to what it entails:

1. Get requirements.
2. Obviously have a schematic of what you want to build. This will have lots of unknown resistor/capacitor/etc. values.

There is a HUGE gap between steps 1 and 2, with a lot of important activity missing. The process (*steve*) posted fills in that gap.

The only thing I would add to what he outlined would be a Step 3.1: Identify the most critical modules, i.e., those modules that have the biggest impact on circuit performance and/or cost.

Then tackle those modules first, doing steps 4 through 7 for each.

This follows the general principle, "take care of the hardest stuff up front, and the rest will be easy."

 

[bonbonbaron]

Thanks guys. So this is what I want to know the most: what exactly does Steve's step #5 entail? That's what I was trying to encapsulate in my steps #'s 3-6.

 

[(*steve*)]

Good point. You may even break down some of these "hard" modules into smaller parts.

The are a lot of other things you could put in there if you wanted. You may have to consider thermal issues, noise, places where high tolerance parts are needed, test points, ease of maintenance, panelising, ease of assembly, ESD protection, documentation, standards compliance, test methods, test jigs, acceptance criteria, failure modes, IP issues, validation, options for second sourcing, pick and place restrictions, devices requiring specialized handling, double vs single sided loads, requirements for ground planes, impedance of signal traces, equalisation of propagation delays along traces, alternatives to obsolete parts, subtle differences between "compatible" parts, isolation requirements, ...

 

[(*steve*)]

An example of a "step 5" task might be the selection of an op amp. Perhaps the circuit requires a certain slew rate, or input offset, our perhaps it is completely non-critical. In the former case you may have a particular device in mind but maybe there is some pressure to use a cheaper part. Can you find one with good enough specs that is available in a suitable timeframe, in the quantities required?

 

[OBW0549]

Thanks guys. So this is what I want to know the most: what exactly does Steve's step #5 entail? That's what I was trying to encapsulate in my steps #'s 3-6.

I would propose doing with Steve's Step 5 something analogous to what I proposed for Step 3: identify those components with special performance requirements, and tackle them first. Some examples would be opamps with very low input offset voltage or offset voltage drift, passive components with tight tolerances, voltage reference chips with tight tolerance and high stability, low noise transistors, and so on and so forth. Other parts can be more "generic."

 

[(*steve*)]

Another step I missed is "research".

You may have to do this even before you determine the requirements because you may not understand what the requirements might be.

More often you may need to do research to discover some alternate approaches to solving a problem where you are unable to satisfy the required specs or you're looking for a simpler solution.

 

[Alec_t]

Research is definitely a first step. From working with Patents (a good source of technical information) I know that the vast majority of invented products/circuits are not totally novel but are developments of existing technology. Therefore, whatever you are designing, there is a high probability that something like it has been done before. This 'prior art' can guide the design process: you may spot some way of improving on it or avoiding pitfalls. If you are designing something for commercial use then you will also need to be aware of what is 'out there', so as to avoid infringing other people's intellectual property rights.