Am I dense or what? - Page 1
Forum section: electronics / beginners

author: simpson
author_rank: Contributor
timestamp: July 03, 2014, 08:58:02 pm
content: 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.htmlI 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?

author: zapta
author_rank: Super Contributor
timestamp: July 03, 2014, 09:03:21 pm
content: It's look like a typo. The bottom net is ground. You can add it yourself ;-)

author: rob77
author_rank: Super Contributor
timestamp: July 03, 2014, 09:10:01 pm
content: typo or not... the schematic is wrong !and the author should have corrected it.

author: Shock
author_rank: Super Contributor
timestamp: July 03, 2014, 09:12:13 pm
content: 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.

author: retrolefty
author_rank: Super Contributor
timestamp: July 03, 2014, 09:22:21 pm
content: Quote from: rob77 on July 03, 2014, 09:10:01 pmI 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.

author: rob77
author_rank: Super Contributor
timestamp: July 03, 2014, 09:26:13 pm
content: Quote from: Shock on July 03, 2014, 09:12:13 pmno one says it's not obviousit'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.

author: simpson
author_rank: Contributor
timestamp: July 04, 2014, 01:09:58 am
content: Thanks for the replies, folks!

author: Richard Crowley
author_rank: Super Contributor
timestamp: July 04, 2014, 01:24:58 am
content: 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).

author: onlooker
author_rank: Frequent Contributor
timestamp: July 04, 2014, 02:56:15 am
content: QuoteInteresting. Do you have a reference on such implied assumptions or on more official example schematics about this?

author: simpson
author_rank: Contributor
timestamp: July 04, 2014, 02:59:46 am
content: 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.

author: zapta
author_rank: Super Contributor
timestamp: July 04, 2014, 03:56:32 am
content: Quote from: Richard Crowley on July 04, 2014, 01:24:58 amThis 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

author: tautech
author_rank: Super Contributor
timestamp: July 04, 2014, 04:18:56 am
content: Quote from: Richard Crowley on July 04, 2014, 01:24:58 amI 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.

author: Richard Crowley
author_rank: Super Contributor
timestamp: July 04, 2014, 04:58:55 am
content: Quote from: tautech on July 04, 2014, 04:18:56 amNO. 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.QuoteAgreed. But perhaps the OP is not experienced enough or confident enough to recognized the assumed parameters.QuoteOr 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.

author: Neganur
author_rank: Unknown
timestamp: July 04, 2014, 05:27:50 am
content: Quote from: Richard Crowley on July 04, 2014, 04:58:55 amThat'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

author: zapta
author_rank: Super Contributor
timestamp: July 04, 2014, 06:55:53 am
content: Also calling a capacitor E1 and a LED L1?

author: bwat
author_rank: Frequent Contributor
timestamp: July 04, 2014, 07:02:53 am
content: Quote from: simpson on July 03, 2014, 08:58:02 pmThis 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???

author: miguelvp
author_rank: Super Contributor
timestamp: July 04, 2014, 07:18:37 am
content: And so is the ground

author: simpson
author_rank: Contributor
timestamp: July 04, 2014, 10:47:00 am
content: 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.

author: Shock
author_rank: Super Contributor
timestamp: July 04, 2014, 11:31:23 am
content: This thread here smells like viral marketing. Especially as that website is one big advert.

author: simpson
author_rank: Contributor
timestamp: July 04, 2014, 11:46:43 am
content: ^ "Viral marketing" by calling attention to a site's inaccurate schematics?I have no connection to the site and do not recommend it in any way.

author: bwat
author_rank: Frequent Contributor
timestamp: July 04, 2014, 12:07:27 pm
content: Quote from: simpson on July 04, 2014, 10:47:00 amMaybe 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?

author: zapta
author_rank: Super Contributor
timestamp: July 04, 2014, 02:14:45 pm
content: Quote from: simpson on July 04, 2014, 10:47:00 amI FYI'ed them about this thread.

author: retrolefty
author_rank: Super Contributor
timestamp: July 04, 2014, 03:07:00 pm
content: Quote from: Neganur on July 04, 2014, 05:27:50 amSo the original author purposely left off the ground term because he assumed his reader base wouldnot have a problem with that? Pff, he simply forgot to add a label.

author: simpson
author_rank: Contributor
timestamp: July 04, 2014, 08:26:56 pm
content: If you look at the base page of the bloghereyou 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.

author: SL4P
author_rank: Super Contributor
timestamp: July 04, 2014, 10:54:37 pm
content: Is it 'signal' Ground, or 'chassis' Ground ?

author: zapta
author_rank: Super Contributor
timestamp: July 04, 2014, 11:03:28 pm
content: Quote from: SL4P on July 04, 2014, 10:54:37 pmIt's a shaky ground. ;-)

author: IanB
author_rank: Super Contributor
timestamp: July 04, 2014, 11:10:25 pm
content: 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.