(is fig b correct in having the 1k2 resistor illustrated there as opposed to the 12k or not at all as the text describes? Also, is the fig referenced (a) referring to (b)? (I highlighted to green))

Safely driving an LED with AC: (a) from 24 VAC, (b) from 240 VAC.
If the LED is driven from a 240 VAC source, the Figure above (a) voltage source is increased from 24 VAC to 240 VAC, the resistor from 1.12 kΩ to 12 kΩ. The power dissipated in the 12 kΩ resistor is an unattractive 4.8 watts.



P = VI = (240 V)(20 mA) = 4.8 watt


A potential solution is to replace the 12 kΩ resistor with a non-dissipative 12 kΩ capacitive reactance. This would be Figure above (b) with the resistor shorted. That circuit at (b), missing the resistor, was published in an electrical engineering journal. This author constructed the circuit. It worked the first time it was powered “on,” but not thereafter upon “power on”.

 

Yes. The capacitor offers reactance, which in this case restricts current flow.

 

Yes. The capacitor offers reactance, which in this case restricts current flow.

Let me clarify:

I was posting a proofread fix.

Fig b should show a 12k resistor or none at all per the text. Referenced fig (a) should read (b) instead.


I understand the theory, Bill.

 

I think you missed the two commas in this sentence:

If the LED is driven from a 240 VAC source, the Figure above (a) voltage source is increased from 24 VAC to 240 VAC, the resistor from 1.12 kΩ to 12 kΩ.

It could be re-written to avoid that confusion, but I don't see the intent to be incorrect as written. The last part of the sentence, after the comma, is missing a verb. Something like, "should be increased" after "resistor" would help.

John

 

I think you missed the two commas in this sentence:

The request was made for proofreaders and suggestions. I did not say it was incorrect, just asking politely.

It could be re-written to avoid that confusion, but I don't see the intent to be incorrect as written. The last part of the sentence, after the comma, is missing a verb. Something like, "should be increased" after "resistor" would help.

John

Just so you all know, I was confused a bit. It basically reads to me fig (a) is an original circuit and fig (b) is a different set-up with modifications to rectify an issue that is not clear ro me or illustrated as I believe was intended.


I would suggest a fig (c) then.



This brings me to a question--- how do you guys signify in a schematic an "either-or" situation or substitution? Is it purely just done in notes?

 

The either/or was the two paragraphs, one refering to schematic a, one refering to schematic b. You phrased the original query as a question, and I answered it!

It is correct as is, all of it. I don't see the problem, you still need a resistor in schematic b to prevent surge, which was explained further down in another paragraph. That particular section I've gone over with a fine tooth comb, and have already done one major rewrite to bring it up to date for modern LEDs.

 

The either/or was the two paragraphs, one refering to schematic a, one refering to schematic b. You phrased the original query as a question, and I answered it! .

Yes you did.

My question was rhetorical in the sence I was being polite and explaining how the reader, a not so advanced reader, may be confused. You wrote it so of course you wouldnt be. Thats the purpose of proofreaders.

Hence the quick clairification in my 2nd post.

It is correct as is, all of it. I don't see the problem, you still need a resistor in schematic b to prevent surge, which was explained further down in another paragraph. That particular section I've gone over with a fine tooth comb, and have already done one major rewrite to bring it up to date for modern LEDs.

If you were not a contributor I wouldnt waste my time explaining myself to you.

Bill, I think you like to just hear it straight so here goes:

My opinion is this: I think it is confusing.

My suggestion is this: Tweek it don't rewrite it.