Electronics > Beginners

Beginners idiot question

<< < (7/8) > >>

vk6zgo:

--- Quote from: mikerj on May 26, 2019, 10:24:38 am ---
--- Quote from: vk6zgo on May 26, 2019, 05:46:28 am ---It's just one of the idiot things simulators do! ;D
Another one is that as a default, LTspice shows an ac source as a DC one, then has a note alongside saying what it really is.

--- End quote ---

LTSpice shows a voltage source as a voltage source.  You then define what kind of voltage waveform you want it to provide.
--- End quote ---

An ac voltage source is not, in normal schematics shown with + & - signs----- a DC voltage source is.
The very presence or non-presence of the polarity signs defines which it is.

Having the default a DC source is misleading.
Standby for multiple "Noobs" becoming confused & drawing real schematics this (incorrect) way.

--- Quote ---

--- Quote from: vk6zgo on May 26, 2019, 05:46:28 am ---I tried to like LTspice---- I really did!, but when it I couldn't simulate a basic CR network, I gave up.

--- End quote ---

This is a PEBCAK problem, not LTSpice.


--- Quote from: vk6zgo on May 26, 2019, 05:46:28 am ---It's a bit like trying to remove cylinder head bolts with a Stilson Wrench------it might work, but it will take 10 times as long, & a lot of scraped knuckles along the way!

--- End quote ---

It's like trying to use a tool you haven't yet learned to use.

--- End quote ---

When I learnt Electronics, the designers of LT spice were but a sparkle in their Father's eyes.

We had a number of ways to determine the operation & performance of circuits.

(1) Use our imagination & our knowledge of theory to visualise how it would work.
(2) Work through the mathematics.
(3) Steal someone else's design.
(4) Build the circuit up & test it in the real world.
(5) A combination of the above.

If I have to devote a not inconsiderable part of my limited time on this Earth to learning how to use a particular underwhelming  "tool", I'd rather use one I know how to use.

And, by the way:- "Get off my lawn!"  ;D

Zero999:

--- Quote from: magic on May 27, 2019, 01:19:02 pm ---
--- Quote from: Zero999 on May 27, 2019, 09:21:16 am ---Only if it's a superconductor.
--- End quote ---
OP is asking about simulation, not real cables.


--- Quote from: Zero999 on May 27, 2019, 09:21:16 am ---Simulators always assume the resistance between ground connections is lower than the wires, which also confusingly have zero resistance. [...] SPICE considers the ground nodes first, so if they're connected together with other wires, then the current in those wires is assumed to be zero.

--- End quote ---
Maybe that's what SPICE does but OP sees exactly the opposite behavior.
It's irrelevant either way, it's just a simulation of "ideal" components which don't exist so it doesn't need to make sense.

--- End quote ---
You're right.

LTSpice doesn't do that. The simulator the original poster is using must do it the other way round: calculate the current in connections before the grounds.

The simple way to avoid this confusion is to not connect more than one ground symbol to a wire.

Zero999:

--- Quote from: vk6zgo on May 28, 2019, 03:06:53 am ---
--- Quote from: mikerj on May 26, 2019, 10:24:38 am ---
--- Quote from: vk6zgo on May 26, 2019, 05:46:28 am ---It's just one of the idiot things simulators do! ;D
Another one is that as a default, LTspice shows an ac source as a DC one, then has a note alongside saying what it really is.

--- End quote ---

LTSpice shows a voltage source as a voltage source.  You then define what kind of voltage waveform you want it to provide.
--- End quote ---

An ac voltage source is not, in normal schematics shown with + & - signs----- a DC voltage source is.
The very presence or non-presence of the polarity signs defines which it is.

Having the default a DC source is misleading.

Standby for multiple "Noobs" becoming confused & drawing real schematics this (incorrect) way.
--- End quote ---
All right, I'll bite.

You've missed the point. SPICE doesn't need schematics. They were added later and there is no default voltage source symbol. LTSpice has both AC and DC voltage source symbols. It's easy to choose the correct one and it's not the software developer's fault, if user makes a mistake and clicks on the wrong one. Even if the user has used the wrong symbol, there's a piece of text next to it clearly showing whether it's AC, DC or both (quite often you want a signal with both AC and DC components).

--- Quote ---
--- Quote ---
--- Quote from: vk6zgo on May 26, 2019, 05:46:28 am ---I tried to like LTspice---- I really did!, but when it I couldn't simulate a basic CR network, I gave up.

--- End quote ---

This is a PEBCAK problem, not LTSpice.


--- Quote from: vk6zgo on May 26, 2019, 05:46:28 am ---It's a bit like trying to remove cylinder head bolts with a Stilson Wrench------it might work, but it will take 10 times as long, & a lot of scraped knuckles along the way!

--- End quote ---

It's like trying to use a tool you haven't yet learned to use.

--- End quote ---

When I learnt Electronics, the designers of LT spice were but a sparkle in their Father's eyes.

We had a number of ways to determine the operation & performance of circuits.

(1) Use our imagination & our knowledge of theory to visualise how it would work.
(2) Work through the mathematics.
(3) Steal someone else's design.
(4) Build the circuit up & test it in the real world.
(5) A combination of the above.
--- End quote ---

That's all well and good, until you work on a project containing hundreds of transistors, etched into a single piece of silicon. It becomes too costly to get an IC made, just to test a concept, hence the need for a virtual breadboard, allowing the designer to test it first. If it wasn't for SPICE, you wouldn't be able to type that message and post it, because the Internet wouldn't exist.


--- Quote ---If I have to devote a not inconsiderable part of my limited time on this Earth to learning how to use a particular underwhelming  "tool", I'd rather use one I know how to use.

And, by the way:- "Get off my lawn!"  ;D

--- End quote ---
That's fine. No one is making you learn how to use it and by the way, get off the LTSpice threads! ;)

Brumby:
Could I please suggest that you not continue this tangent "discussion" on this thread.

This is the beginners section and we don't need to bury the Op in stuff that isn't directly helping him.

vk6zgo:

--- Quote from: Brumby on May 29, 2019, 02:00:50 am ---Could I please suggest that you not continue this tangent "discussion" on this thread.

This is the beginners section and we don't need to bury the Op in stuff that isn't directly helping him.

--- End quote ---
Why not! ---- That's what we always do! ;D

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod