12V car cig lighter adapters - safe?

[Andy Hall]

Gosh.

So we're waiting. How about you demonstrate how you arrive at the answer using first principles and impress us with your prowess.

[Graham]

I'm still waiting for the answer. Why the childish comments? Its so dam silly. You can make those comments if you wish. Its water off a ducks back to me as I know what I am talking about. I suppose it helps to restore your position by attempting to make me look silly or small, but it really is so stupid.

Its now becomming pointless asking you for the answer as the online tool can provide it. But at least it owuld show some slight understanding of it now.

Lets make it more realistic and see how long it takes to find an online calculator for this:

What would be the resonant frequency for a 100pF capacitor and a 10uH coil?

That took me about a minute on the calculator once I got the (10 to the minus 12 and 10 to the minus 6 bits clear in my bonse). I am pretty dumb, but I learnt my skills well as it interested me greatly at the time and that is why I object to cowboys pretending to know my trade when they do not.

Graham

[Graham]

How's your IQ today Frank?

[Andy Hall]

So there you have it. A statistical sample size of two.

[Graham]

OK tosser.

You are not worth the time, but here we are for the record.

Its ever so simple:

Xc (Capacitive reactance) = 1 divided by 2 x pi x F x C

So:

470uF = 470 x 10 to the minus 6 x 50 = 0.0235

2 x pi = 6.28

6.28 x 0.235 = 0.147

1 over 0.147 = 6.77

This is VERY, VERY basic electonics. Very basic.

I wasn't asking anyone to write it all out like this, just the answer would have been proof enough you knew what you were talking about. No point continuing now as you will just make childish comments of "As we already knew" etc. You didn't know, so in future be honest to yourself and then you might start to open your mind to learning agian.

Now you guys carry on with your bad selves. Try not to read the sun too much and be honest about what you do and do not know. Now feel free to slag me off to get your position ans status back again. Oh, and do try and widen those narrow minds a bit.

Graham

[Andy Hall]

It was pointless in the first place.

w = (1/(sqrt(LC)))

where L is the inductance in henries and C the capacitance in farads.

w = 2 * pi * f

allowing calculation of the resonant frequency in hertz.

The main point with this one is not the formula but the sanity check on the order of magnitude.

I've never seen any of this as a trade. Not that there is anything wrong with trades other than they generally have a limited scope. For myself, I've never accepted pigeon holing or glass ceilings.

[Andy Hall]

So why did it take you so long?

I gave you the formula to do this yesterday.

You mentioned that you wanted it with 7 characters. I am not sure what that's about, other than if you were hoping for an answer to 7 significant figures.

So why did you make such a song and dance about it?

Keeping an open mind about learning as opposed to training has always been my principle, but you're welcome to borrow it and try it out

Oh dear....... ;-)

[Conor]

Why are you asking a question which can be answered in a few seconds following a quick google search?

I'll ask you one, seeing as you're so knowledgeable. It was done in the first few weeks of my BTEC ONC course so shouldn't be too demanding for you. It was done as a lesson in compact circuit design where the aim was to build a flipflop to the smallest size possible with set components. I won. So as what I did isn't exactly hard for anyone with a brain to work out and I'm regarded in ukrm as just a thicko knuckle dragging yorkie munching lorry driver, you who claims you're a competent electronics engineer, will have no problem with the answer. Oh, only downside is it's not something you're going to find using Google.

"When building a simple flipflop circuit using a pair of LEDs, capacitors, resistors and 2 BC108's, what can you do to reduce the size to the smallest possible, explaining the reason why? "

[Conor]

We'll see just how competent Graham is. I've just asked him a question which I can guarantee you will not find anywhere on Google.

[tony sayer]

I

Course you wouldn't say that to someone in lets say a bar in Montana now would you?, very polite society there;)..

Well perhaps you wouldn't say it again .. ever;

[Andy Hall]

That's much more interesting. When you say smallest, do you mean smallest number of components; and which type of flipflop do you mean?

[The Natural Philosopher]

You and me both.

[The Natural Philosopher]

Anybody who thinks that m,erely being able to calculate the resonant frequency of an LC circuit is the be all and end all of electronic engineering, is a lot dumber than he thinks...

Try a stochastic analysis of mean path delays through a digital circuits over the full temperature range..

Or trying to get a > 60db noise figure from a 1uv 100MHZ front end running 3 inches away from a load if ECL and Schottky TTL logic..

I'm with Andy here, unusually. one over root 2 pi l c is something you learnt to pass an exam: afterwards, you used a table..;-)

[Andy Hall]

Ah so you've done that as well..... One of my first projects was the design of hybrid frequency synthesisers using the logic families you mention as well as CMOS in order to reduce power consumption and then digital as well as analogue filtering for the PLL. There were some basic filter equations that could be used to make sure that there was at least theoretical stability, but then it became much more empirical. For example the construction and mounting of the oscillator components was critical to avoid mechanical disturbance causing microphony. Even the choice of FETs was vital From the same manufacturer there could be a substantial difference to noise behaviour depending on the factory and the packaging method of the device.

It became more entertaining when microprocessor based control systems were added. Only a single supply rail was available (mobile equipment) and most MOS microprocessor devices and peripherals were two or even three rails. Hence the code had to be burned into low power bipolar proms (at £50 a pair) making development expensive. The uP subsystem had to be powered on and off several times a second to reduce power consumption from the batteries. All of this in very close proximity to a receiver that was wide open over a wide frequency range and a spec that meant that only a few spot frequencies were allowed to be unusable.

The hours I spent in Faraday cages without air conditioning and in contortions in vehicles to get it all to work. Many interference interactions could be found and fixed but would often make others worse.

Some aspects are probably better now as the result of VLSI technology and ASICS, but I think that anything involving RF either purposefully or accidentally will always have a green fingers element to it - and I don't mean he staining from copper and brass shielding.

[Duncan Wood]

You could always get a decent calculator. HTH. HAND.

[Conor]

I've given you the component list.

4x resistors (value irrelevent for this question but low wattage ones) 2x capacitors (value irrelevent for this question) 2x LED 2x BC108

There is only one type of flipflop you can build using those components.

[Andy Hall]

You didn't provide the quantities of components or the objective. Now you are specifying the complete list of components, so now what is the meaning of smallest? Do you mean that all of the components must be used or may be used?

[Andy Hall]

If you are going to use all of the components that you mentioned, then the circuit can be a classic one as follows:

- Emitters of both transistors to negative rail

- Collector of each transistor connected via LED and a series resistor to positive rail

- Base of each transistor connected via resistor to positive rail

- Capacitors connected from collector of each transistor to the base of the other.

Result is astable multivibrator.

[PCPaul]

Or try to get any useful answer at all from a polarimetric many-GHz radar system with a 500MHz IF and ultra-sensitive sample-and-holds/ADCs when some sod puts up a mast transmitting 10W or so at about the same frequency just outside the window..

Or a calculator for those of us a bit younger ;->

[tony sayer]

No its not!. RF is quite understandable you just have to have Green blood flowing in yer veins;)...