fmtransmitter????poor design

SgtWookie

Joined Jul 17, 2007
22,210
The owner of that site is some Aussie named Colin Mitchell who likes to take things out of context so that he can "find the mistakes".

He created a userID on this site, but he only lasted about a week before he was shown the door.

Someone tried to build a transmitter from a schematic on the Internet, and it wasn't working. AudioGuru patched up the design enough to make it work. It's that simple.

While stripboard would not be something that I would particularly want to build an RF circuit on, it does have the advantage of being easily replicated by a less experienced person; just make sure you count the holes right, and cut the traces in the right places. I would use the "dead bug" technique for a one-off RF circuit; but those are harder to replicate.

The text and image below were found on this page:
http://www.talkingelectronics.com/projects/SpotMistakes/SpotMistakesP10.html

there is a circuit that Bill_Marsden drew up basically as an exercise, not a practical circuit:


And then, Colin's rant:
Here's a circuit from "All About Circuits:" It has three technical faults; Can you spot them?

Firstly the Darlington transistor is not needed. It can be an ordinary transistor. And it doesn't have to be a "power" transistor. The circuit is taking a maximum of 25mA
Secondly, the 75R current limit resistor does not give very much tolerance for changes in supply voltage. A change of 1v will alter the current through the LEDs by 13mA. Most LEDs run on 15-25mA MAX and if the voltage drops by 1v, they will dim considerably.
And thirdly, the 470R resistors do NOTHING.
I also have another point of disagreement. Why use 18v to drive 6 LEDs. Since only about 11v is needed, you are wasting over 40% of the energy from the batteries.
You could drive 8 LEDs from a single battery as 4 LEDs in one string and 4 LEDs in a second string, and use less energy.
If you are going to design a circuit and add components such as the 470R resistors above, test the circuit to see if they have any effect.
This is one of the last things I do when designing a new circuit.
I gradually remove each component to see if it has any effect. Sometimes I have removed over 10 components that had little or no effect on the performance.
And sometimes a re-design results in 3 or 4 fewer components.
It's very embarrassing to find someone has omitted 10 components and the circuit works exactly the same.
Don't let this happen to you. Ask yourself, "What is each component doing?"
He completely missed the point of the circuit; which was to allow LEDs to be gradually faded on and off sequentially via potentiometer R8, without having to use a bunch of comparators or opamps.

First one has to be able to comprehend what the intended purpose of the circuit is, before one can start re-engineering it. Had the suggested changes been implemented, it might work; but for something completely different than the original application.

So, Colin Mitchell gets awarded yet another engineering failure.
 

Wendy

Joined Mar 24, 2008
22,146
AG is very active at this site, as well as ElectroTech. I suspect Mr. Mitchell may have bitten off more than he can chew, AG can clean his clock several different ways, knowledge, experience, willingness to exert himself helping others, and not least, personality.

Collin55 is my own personal troll at ElectroTech. AG has a much better reputation there. Between the two I would trust anything AG has said or built hands down, AG has a real degree and retired from many decades of active work, the same is questionable of Mr. Mitchell.

If anyone cares, I go by QuietMan at ElectroTech. There is no relation between the two sites, but they are so similar in many ways I consider it a sister site.

My own version of spot his mistake:
Here's a photo mistake. Can you spot the mistake?



The boy is soldering a "Solderless Breadboard!"
Either he doesn't know there are PCB versions of solderless breadboard, or he doesn't care. My vote is on the latter, he likes tearing other people down to build himself up. It is who/what he is.

For anyone interesting in the breadboard, it is available from Radio Shack,

http://www.radioshack.com/product/index.jsp?productId=2102846



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Wendy

Joined Mar 24, 2008
22,146
Found another one, this guy loves me!

Here is a circuit that is over-designed:



It can be simplified to this:



Before designing a circuit, look on the web and carry out research to see what has been done by other designers.

Apart from the first circuit producing a very weak output, it uses a lot of components. The second circuit produces a very bright flash and although it is not extremely efficient in current consumption, (the 47R is placed across the supply during the short flash-period), it will work on a supply down to 2v.
He originally claimed this circuit would not work, of course I test everything for the AAC book. So now it is over designed, I wonder if he ran the 3 month battery test like I did (it lasted past a month). Mine is verified over time and was overdriving the LEDs, not so sure of his, but then, his ego is not supported by his talent, so he has to tear the perceived competition down.

Here is the article:
CMOS 555 Long Duration LED Flyback Flasher

If he was as half as smart as he thinks he is he would have noticed my circuit is driving a 5.1V LED drop (it can handle even more LEDs in series), while his is driving a single LED. But this genius thinks they are equivalent.

He also doesn't get demonstration circuits for teaching, but then he has books he wants you to buy. He has a component called a TE555 as part of a kit he sells. It is a PIC, typical of the deceptions he likes to use.

Besides, my drawings are much prettier! :D

You will note he posts these entries without giving the writers a chance to respond. Again, it is part of who and what he is.

Dagnabit, I'm just going to have some ice cream and cool down!

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Audioguru

Joined Dec 20, 2007
11,249

SgtWookie

Joined Jul 17, 2007
22,210
I think he was referring to his circuit not working, as it's a flat-liner in LTSpice. One blip at ~500mS, and then it's dead.
 

Wendy

Joined Mar 24, 2008
22,146
It is possible the extra capacitance is helping your circuit, but it is kind of hard to model something like that.

Anytime Collin can't understand something it can't work, even when you show it working. :confused: :rolleyes:
 

T.Jackson

Joined Nov 22, 2011
328
Yeah there are some nasty people around. Think that I have met most of them. No one likes a know it all. You get one point in an IQ test for ticking yes to "true knowledge is knowing nothing at all" That's fact. Go and argue with the guy who wrote it. Guys who write tests like this have pHDs and stuff.
 

T.Jackson

Joined Nov 22, 2011
328
Anyhow, I should probably change my name to "Silent Project Contributor".
I have some really good projects for you to build next year. I am certain that there will be arrogant critics, but such is life.
 

thatoneguy

Joined Feb 19, 2009
6,359
He completely missed the point of the circuit; which was to allow LEDs to be gradually faded on and off sequentially via potentiometer R8, without having to use a bunch of comparators or opamps.

First one has to be able to comprehend what the intended purpose of the circuit is, before one can start re-engineering it. Had the suggested changes been implemented, it might work; but for something completely different than the original application.

So, Colin Mitchell gets awarded yet another engineering failure.
He must do that on purpose, since he NEVER posts the links back to where they came from, other than a base URL like "AAC". If he did post the link to the writeup that goes with the circuits, he would look like a fool. Instead, he creates his own writeup on what he thinks the circuit should do, as Wookie stated. It outright lies when you look at it in that context.

Sadly, there's probably a lot of people that go to that site and think he fixes everything, not being aware of the other forums. A while back I remember he said that the single transistor "Joule Thief" circuit that was all over instructables.com wouldn't work, and he re-designed it with triple the parts.

The problem is the one he was tearing down and redesigned was called "The Minimalist Joule Theif", but he cut that title out of the schematic. It did, in fact, work, though he stated it couldn't, he must not have built it or understood it.
 

T.Jackson

Joined Nov 22, 2011
328
There is also much BS going around too. I see stuff and I tend dismiss it as non-genuine rather quickly as habit. I trust old books though.
 
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