Wow, do I feel old. I used to build the circuit on a protoboard and if it didn't work.... I figured out why and changed things until it did....and then, when the circuit doesn't work, you can enter it into the simulator so that it can show you why it doesn't work...
Because to get a finished design you have to build it up. You can sim it and then build it or you can build it and do the development on the prototype and then you're done. I like doing things the easy way, but the difference is I had to deliver working designs. People who rely on sims don't.... unless they build them which is step #1 in my process.It's interesting the number of simulator Luddites on these forums.
A simulator is just a tool. If you don't want to use one fine, but why act like those who do are somehow wasting time?
Yes some circuits will simulate but not work when built, but it's rare for a circuit to not simulate correctly
Not a universally true statement. But I would also say that the process of troubleshooting the circuit (even if more time intensive) yields a lot more learning than punching numbers into a sim until it outputs what you need. The troubleshooting process forces one to actually learn how the circuit works.And I've trouble-shot enough circuits to know that finding the problem in a simulator is a lot easier than finding it in a (non) working circuit.
Simulations for phase margin and stability calculations caused more problems than the others combined. The sims could never comprehend the effects of things like bond wire inductance. We had three different regulator products released by the design group that later were found to be unstable under conditions they never tested.... just simulated. The LP3963 got out unstable and cost the company many millions when we were sued by Japanese companies to recover their wasted product and rework cost on parts that did not work as advertised. That got up to the CEO (Halla) and we were issued a blanket warning that the next oscillator was going to mean people fired. But the designers still used sims for "test data".I was given an op amp circuit at work that was exhibiting instabilities and I was asked to trouble-shoot it.
The least you can do is not quote me out of context to make a point.crutschow said: ↑
Yes some circuits will simulate but not work when built, but it's rare for a circuit to not simulate correctly
rare?
My whole career was helping customers who found their way to that rare occurrance. I don't mind if people use sims as long as they finish the job and check the design with reality. But most people don't. They are lazy and allergic to the lab bench and they end up with non functional prototype units and they call me..... to gripe about the crappy Spice model
OK, then I really don't get the point of your statement. It's rare for it to simulate as not working but still work in practice? Who would care if that happened, that would be fine, you would end up with a working circuit. What we are discussing is the chronic use of sims which show a circuit working which does NOT then work in reality, and the labeling as luddites as those who believe that building the circuit should be the development cycle.The least you can do is not quote me out of context to make a point.
My full statement was: "but it's rare for a circuit to not simulate correctly (other than simulator problems such as convergence issues) but still work in practice."
You seem proud of the fact that you'd rather do it the grunt way and debug your breadboard rather then use a tool that could help you avoid many of those bugs before you built it. I don't really understand that reasoning but to each his own.
I fully realize that you have to breadboard the circuit before you release the design. Never implied that you shouldn't
But it can save a lot of effort and redesign and lengthy troubleshooting if you simulate the design as best you can with estimated parasitics and component tolerance variation before you build it, is all I'm saying.
Try doing a Monte Carlo test of component tolerances with a breadboard circuit.
I've had to deliver working designs for military and space systems, and I simulated them first before I built them. That saved me a lot of grief.
But that's not what they are being used for. Just read the posts on this forum if you want examples. In 20 years I never saw a single person using one for that. They all use them in system sims to replace discreete components to avoid building prototypes.But it can save a lot of effort and redesign and lengthy troubleshooting if you simulate the design as best you can with estimated parasitics and component tolerance variation before you build it, is all I'm saying.
I have had to fix lots of designs where people just kept changing components on a bread board "until the prototype circuit worked", and on that basis, they put it into production. Then they hired me to figure out why they had 25% fail rates at final test.Wow, do I feel old. I used to build the circuit on a protoboard and if it didn't work.... I figured out why and changed things until it did.
...
Did you see the legal disclaimer TI has added to NS data sheets I posted:
"Customers should validate and test their design implementation to confirm system functionality."....
Apples and oranges. What we are talking about is using sims in place of building or actual bench data which is what they are used for about 99% of the time in both system design and IC design.I have had to fix lots of designs where people just kept changing components on a bread board "until the prototype circuit worked", and on that basis, they put it into production. Then they hired me to figure out why they had 25% fail rates at final test.
Simulation is the key to finding how the circuit is effected by component tolerances, voltage, thermal and environmental conditions.
How are you supposed to build a VLSI chip (millions of transistors) using breadboarding when a single IC production run costs $millions? Simulation is used extensively (and exclusively) in IC design.
So... you read the following:Which does not say that a customer should not simulate their design. It doesn't say how the customer should validate their design, just that they should.
Maybe so. There are plenty of clueless "designers" out there.I have had to fix lots of designs where people just kept changing components on a bread board "until the prototype circuit worked", and on that basis, they put it into production.
So... you read the following:
" Customers should validate and test their design implementation to confirm system functionality. "
and think that a simulation qualifies as test confirmation that the system will function as designed?....
Speaking of inventing words......You think that the disclaimer says that simulation is no good. It doesn't!!!
I think that the disclaimer says: Customers should validate and test their design implementation to confirm system functionality by any means possible, including simulation (emphasis mine).
I am not blaming as much as I am WARNING that sims should not be used as a substitute for bench data..... and that is exactly how they were used in about 99% of the cases I have been involved in.It sounds to me that you are blaming the tool when in fact you should be blaming the users who are using the simulations as their test bench.
If you think that's what you need, that's fine. What you don't realize is how many people think #2 is an adequate substitute for #3 (just read the post 95 above). What I am saying is there are plenty of good designers who don't need #2 and go straight to #3. My gripe is with people who skip #3 and then call the company's apps line or start posting all over the internet looking for people to do their job.Hello there,
On the design and testing of circuits, there is an order that is most logical.
1. First comes circuit theory. The more you have of this the better.
2. Second comes simulation. This helps to validate the theory and operation.
3. Third, breadboarding.
4. Forth, field testing.
5. Production.
I fail to understand why anyone would put a battery charging circuit on a Lead Acid battery since lead acid batteries are self regulating. A battery that is very low will take a high charge but as the battery becomes charged it takes less and less charge. When the battery is almost fully charged it will take almost no charge.
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