Author Topic: Am I dense or what?  (Read 6977 times)

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Offline simpson

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Am I dense or what?
« on: July 03, 2014, 08:58:02 pm »
I was looking at a simple circuit posted on an electronics blog and, as I see it, it wouldn't work.

Here is the circuit:


http://www.electronics-project-design.com/LEDCircuit.html

I don't see the circuit as workable since it lacks a ground. How can you power a circuit with a +9v supply and have no ground?

I posted a comment beneath the circuit asking if there wasn't a ground missing but the comment was removed with no reply. Am I missing something? In the upper left corner of the schematic it appears that only one terminal of the battery is connected. Is this my misunderstanding? Does this sort of symbol mean that both terminals are connected. If so, how?


 

Offline zapta

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Re: Am I dense or what?
« Reply #1 on: July 03, 2014, 09:03:21 pm »
It's look like a typo. The bottom net is ground. You can add it yourself ;-)
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Offline rob77

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Re: Am I dense or what?
« Reply #2 on: July 03, 2014, 09:10:01 pm »
typo or not... the schematic is wrong ! ;) and the author should have corrected it.
 

Offline Shock

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Re: Am I dense or what?
« Reply #3 on: July 03, 2014, 09:12:13 pm »
What gives it away is the schematic indicates the capacitor is polarized (has a positive and negative side) and the NPN transistors emitter is also pointing the same way and you can verify that by seeing how the diodes are connected to the transistors collector.
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Offline retrolefty

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Re: Am I dense or what?
« Reply #4 on: July 03, 2014, 09:22:21 pm »
typo or not... the schematic is wrong ! ;) and the author should have corrected it.

I agree. It's not a typo it's an omission. A typo is when one misspells something, an omission is something the author forgot to add.
 

Offline rob77

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Re: Am I dense or what?
« Reply #5 on: July 03, 2014, 09:26:13 pm »
What gives it away is the schematic indicates the capacitor is polarized (has a positive and negative side) and the NPN transistors emitter is also pointing the same way and you can verify that by seeing how the diodes are connected to the transistors collector.

no one says it's not obvious ;) it's actually so obvious that many of us will not even notice the error at the first sight.
actually when i opened the thread i was starring at the schematic... what's wrong ? nothing !!  i realized it's missing GND just after reading the full post..

but anyways...  the schematic is wrong... for us it's obvious where's the GND... but for a young player building his very first circuit it's not... so the author should have corrected it immediately and not delete the OP's comment.
 

Offline simpson

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Re: Am I dense or what?
« Reply #6 on: July 04, 2014, 01:09:58 am »
Thanks for the replies, folks!
 

Offline Richard Crowley

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Re: Am I dense or what?
« Reply #7 on: July 04, 2014, 01:24:58 am »
Whether the diagram is really "wrong" is debatable.  And that is likely why your objection was removed without comment.

Even if not labeled, the top bus/node is assumed to be power and the bottom is assumed to be ground unless otherwise stated.

The main reason for the power notation in the upper left corner is to establish the design voltage (and secondarily, the polarity). 
Ground is simply assumed (for better or worse).
 

Offline onlooker

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Re: Am I dense or what?
« Reply #8 on: July 04, 2014, 02:56:15 am »
 
Quote
Even if not labeled, the top bus/node is assumed to be power and the bottom is assumed to be ground unless otherwise stated.

Interesting. Do you have a reference on such implied assumptions or on more official example schematics about this?
 

Offline simpson

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Re: Am I dense or what?
« Reply #9 on: July 04, 2014, 02:59:46 am »
The other schematics on the blog that I saw all had a GND symbol but not this one. So, I believe it was mistakenly omitted.
 

Offline zapta

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Re: Am I dense or what?
« Reply #10 on: July 04, 2014, 03:56:32 am »
Whether the diagram is really "wrong" is debatable.  And that is likely why your objection was removed without comment.

This is inconsistent with the rest of the diagrams in that site so if not an error it's sloppy.

Edit: oops, somebody already said it. +1 then :)
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Offline tautech

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Re: Am I dense or what?
« Reply #11 on: July 04, 2014, 04:18:56 am »
Whether the diagram is really "wrong" is debatable.  And that is likely why your objection was removed without comment.

Even if not labeled, the top bus/node is assumed to be power and the bottom is assumed to be ground unless otherwise stated.

The main reason for the power notation in the upper left corner is to establish the design voltage (and secondarily, the polarity). 
Ground is simply assumed (for better or worse).
I wonder if you and others would be of the same opinion if the +9V node had been omitted?

In short the OP is not dense, whoever posted this circuit is.  :palm:
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Offline Richard Crowley

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Re: Am I dense or what?
« Reply #12 on: July 04, 2014, 04:58:55 am »
I wonder if you and others would be of the same opinion if the +9V node had been omitted?
NO. I would agree that the circuit was incomplete.  If for no other reason than that the design voltage is not revealed.
Anyone with more than a few weeks experience reading schematic diagrams should be able to derive which is ground and which is the supply rail upon inspection. The polarity of the transistor (and the LEDs and the electrolytic capacitor) reveals that this is a negative-ground, positive-supply rail circuit.

Quote
In short the OP is not dense,
Agreed. But perhaps the OP is not experienced enough or confident enough to recognized the assumed parameters.

Quote
whoever posted this circuit is.
Or perhaps the editor or website owner is making an assumption about the skill-level of his readers that doesn't match the OP's situation at this time.
 

Offline Neganur

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Re: Am I dense or what?
« Reply #13 on: July 04, 2014, 05:27:50 am »
Or perhaps the editor or website owner is making an assumption about the skill-level of his readers that doesn't match the OP's situation at this time.

That's a really poor justification and a bit far-fetched assumption about the author (I think it's pretty obvious that the missing GND is a genuine oversight).
Incomplete circuit diagrams just confuse newbies unnecessarily :)
 

Offline zapta

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Re: Am I dense or what?
« Reply #14 on: July 04, 2014, 06:55:53 am »
Also calling a capacitor E1 and a LED L1? 
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Offline bwat

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Re: Am I dense or what?
« Reply #15 on: July 04, 2014, 07:02:53 am »
I posted a comment beneath the circuit asking if there wasn't a ground missing but the comment was removed with no reply.
This is the really shocking part!

Actually, check out the website again folks: http://www.electronics-project-design.com/LEDCircuit.html. And the comment is back???

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Offline miguelvp

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Re: Am I dense or what?
« Reply #16 on: July 04, 2014, 07:18:37 am »
And so is the ground :)
 

Offline simpson

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Re: Am I dense or what?
« Reply #17 on: July 04, 2014, 10:47:00 am »
Aha! That's funny because I posted the comment on June 22nd and it wasn't there when I started this thread on July 3rd. But, within one day of posting here the comment magically appeared.  ;D
« Last Edit: July 04, 2014, 10:53:09 am by simpson »
 

Offline Shock

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Re: Am I dense or what?
« Reply #18 on: July 04, 2014, 11:31:23 am »
This thread here smells like viral marketing.  Especially as that website is one big advert.
« Last Edit: July 04, 2014, 11:33:25 am by Shock »
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Offline simpson

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Re: Am I dense or what?
« Reply #19 on: July 04, 2014, 11:46:43 am »
^ "Viral marketing" by calling attention to a site's inaccurate schematics?  :-DD

I have no connection to the site and do not recommend it in any way.
 

Offline bwat

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Re: Am I dense or what?
« Reply #20 on: July 04, 2014, 12:07:27 pm »
Aha! That's funny because I posted the comment on June 22nd and it wasn't there when I started this thread on July 3rd. But, within one day of posting here the comment magically appeared.  ;D

Maybe Mr. Chiok has it set up so that comments aren't automatically posted and he didn't know your's was awaiting moderation until he saw your thread here?

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Offline zapta

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Re: Am I dense or what?
« Reply #21 on: July 04, 2014, 02:14:45 pm »
Aha! That's funny because I posted the comment on June 22nd and it wasn't there when I started this thread on July 3rd. But, within one day of posting here the comment magically appeared.  ;D

I FYI'ed them about this thread.
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Offline retrolefty

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Re: Am I dense or what?
« Reply #22 on: July 04, 2014, 03:07:00 pm »
Or perhaps the editor or website owner is making an assumption about the skill-level of his readers that doesn't match the OP's situation at this time.

That's a really poor justification and a bit far-fetched assumption about the author (I think it's pretty obvious that the missing GND is a genuine oversight).
Incomplete circuit diagrams just confuse newbies unnecessarily :)

 So the original author purposely left off the ground term because he assumed his reader base would
not have a problem with that? Pff, he simply forgot to add a label.
 

Offline simpson

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Re: Am I dense or what?
« Reply #23 on: July 04, 2014, 08:26:56 pm »
If you look at the base page of the blog here you can see that he calls this schematic "LED Circuit That Anyone Can Do" which implies that it is for beginners, etc.

But, I don't want to grind this into the ground (no pun intended). We all make mistakes. I just wanted to clarify that one point.
 

Offline SL4P

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Re: Am I dense or what?
« Reply #24 on: July 04, 2014, 10:54:37 pm »
Is it 'signal' Ground, or 'chassis' Ground ?  ;)
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Offline zapta

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Re: Am I dense or what?
« Reply #25 on: July 04, 2014, 11:03:28 pm »
Is it 'signal' Ground, or 'chassis' Ground ?  ;)

It's a shaky ground. ;-)
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Offline IanB

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Re: Am I dense or what?
« Reply #26 on: July 04, 2014, 11:10:25 pm »
When I was growing up in the UK the convention for construction projects was always to put the power source explicitly on the circuit diagram with a symbol and a label, e.g. "9 V battery". Not only would this make the power rails clear, it would also give an indication of the expected power source when building it.

I see the use of "voltage rails" and "ground rails" as a convenient shorthand for engineers, but it doesn't always aid reading comprehension.
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