trash

It might be time to consider another carear path ?
Maybe not Plumbing either ?

z80

I can't believe that people expect to be able to understand a complex integrated circuit without doing the basics like current flow theory.

It all comes down to the fact that those who don't know jack about electronics always reckon they can "pick it up" in an afternoon.

It's all this do it yourself, assemble the kit...without any idea on how it works type of mentality.

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bulbous

Many don't even manage to get step-by-step kits going properly....mostly because they can't read and understand the written word well enough, but sometimes because they assume little thought is required.

Like many of the experienced technicians on Austech I will go out of my way - and offer my time to anyone - on the proviso that the person needing the help is not lazy and has made a genuine effort first.

I had a young country fellow bring his kit-built amplifier into the workshop (he was prepared to pay service rates for me to 'have a quick look') and on first inspection it looked neat and tidy with nicely placed components and even the colour bands of the resistors all the same way around....then I turned the PCB over to have a look at his soldering !

He had used AIRFIX plastic modelling cement to glue the bits in.......

........so I showed him a bottle of acetone and told him to come back when the thing was cleaned up after he had pulled all the bits off the board. I sat this bloke in a spare workshop position and set him up with a WELLER, gave him a lesson in soldering and in no time (well, slow really !) his amplifier was making noises. This bloke is now quite proficient at kit building and helps others, which for me is the buzz.

The junk '20-in-one' and '100-in-one' type do-it-yourself boxes seen at shops like TANDY etc. are a complete waste of time - kids just follow the steps and connect things up and learn absolutely nothing about theory - most kids just want instant gratification. Some of the Dick Sniff Electronics "Fun Way" projects were a little better in that at least they had a circuit explanation, but still offered limited value in terms of a real grounding (!) in theory.

If anyone wants to work with electronics it is imperative that they learn the basics, and for many this will mean extra study in mathematics. When you have the basics you can start to learn the tricks ! A good sharp technician can fix many faults without a service manual or even a circuit diagram, much of this insight coming, of course, from experience. In fact I have a line for whining customers along these lines -

"Yes Sir, the repair invoice total is $85 - $15 for the parts and $70 for knowing where to put them".......

The guts of the electronics world is - if you don't want to study and learn, including the shitty mathematics, you are wasting your time. Not everyone can learn electronics - the really clever ones probably don't want to !

For me the service game is over, now I concentrate on my own gear for Amateur Radio and etc.,....and I have never enjoyed it more.

trash

Interesting ... maybe they have deteriorated since I was a kid.
I had a 20 in 1 that my folks gave me when I was 7yo. That was a BIG mistake.
Naturally there isn't a lot you can do with 20 circuits, but the explinations of how each circuit worked were simple and clear. Simple enough that a 7yo could understand how they worked. The manual is very much like the Dick Smith books. Very simple, but I do think that is what is required for people who don't have anybody looking over their shoulder to help guide them.
Nobody in my immediate or distant family is electronically minded, so I can only put down my learning foundation to that kit.

I have noticed kids today have changed from when I was that age.
I was programing computers when I was 8yo. While my friends were playing games, I was writing them. CP/M machines didn't have much to offer in graphics back then.

I help out with JOTA. 20 years ago kids were still amazed that they could talk to people on the other side of the world for free or transmit their own television pictures.
Today, this is old news. Internet, mobile phones, and video phones make such technology seem trivial. At JOTA scouts have no interest but playing network games on the internet. Nothing we organise seems to be able to fire their interest. Even the smartest of the bunch who thinks he's a hacker is usually nothing but a skript kiddy.

The cubs on the other hand are full of wonder and amazement. They seem to lack the corruption of the modern world. I set up enough material for the scouts to build crystal radios. Winding a coil was too much effort for the scouts. The cubs (<10yo) took pride in their work. Even the kids who were not so handy were amazed that they had made a radio that worked on nothing was made from junk.
Anything and everything fascinates them.

One old rotory dial phone was all that was required to make a radio. All the parts can be found inside. But sometimes germanium diodes and maybe a tuning capacitor can be bought from jaycar to make it better.

I'm constantly looking for new ideas and circuits that are simple to build that will corrupt these young minds into science and engineering carears !

z80

I can teach you how to make a radio with a needle and razor blade trash


as long as the blade is as old as you obviously are....



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best4less

I thought I made one about 200 years ago LOL

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z80

damnit...thought I was the only one

Though the selectivity looks sus on your one

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LeroyPatrol

well bugger me you guys aren't talking crap!

NEODUX - make love not work

I remember using an OA95 with an ear piece as a kid. Got 3mp or 3kz (not 3xy hehe)

Leroy

trash

Yes Z80, you might have also discovered that you can use just about any two dissimilar conductors to produce a slight rectifying effect.
My favourite material is graphite, (pencil lead) on any metal, especially razor blades.
Galena as a minerial is always fun to use. Lead is in the same group as Carbon, Silicon, Germanium and Tin all of which are used for their rectifying properties as well as some of the elements in the neighbouring groups.
Want a good crystal radio project ... make your own diode by growing tin whiskers on a substrate.

I've been meaning to make an FM crystal radio using a cavity and a germanium ratio detector. I'll get around to it one day.

My last weird arse project was to make a glass of water transmit are radio signal !
I can hear the crowd shout "BULLSHIT" ! So I'll describe the process.

The first task is to make the water a semiconductor.
A salt makes the water conductive, a metal probe provides the dissimilar conductor.
That part is simple, you already have the basis for a glass of water crystal radio. (yes it does work Z80).
The trick to making a diode transmit is that you need it to have a negative resistance. An example of a real diode that does this is a Tunnel Diode.
Tunnel diodes were used in all kinds of oscillators, a variation of the tunnel diode is a Gunn Diode, used in microwave modules and police radar etc.

So how do you make a glass of water have a negative resistance ?
Choose the type of salt and the metal probe carefully.
Borax and Aluminium are a winning combination.
Aluminium is very easy to come by, borax used to be found at chemists* but because everybody is a terrorist, you'll have to buy it at the local garden shop.
The Aluminium needs to have the smallest point contact possible. I use aluminium cans split to form an aluminium splinter and the point just touching the surface of the water.

You can test the negative resistance of your glass of water with a voltage divider and a milliammeter. The ammeter will drop as your raise the voltage across the diode, this is the negative resistance region and the voltage that you need to run your diode at. If you have a spectrum analyser (I do) you will notice RF noise coming from the glass of water !

So now it's just a matter of cleaning up all that RF power.
A tank circuit does it nicely ! I wind a coil around the glass using it as the former. A bit of clever engineering I have a metal plate (aluminium foil) on the top and bottom of the glass to make a capacitor.

Apply the power and VOLA ! A carrier appears.
That's how you make a glass of water transmit !

I find that most of my carriers end up in the HF section of the band anywhere from about 5 to 20MHz depending on coil windings.

Just in case you're thinking that DXCC on a glass of water is going to be possible, the best output power I've managed to achieve has been about -20dBm, or 10uW which is a very tiny signal.

But even with this tiny amount of power, you can use a shortwave radio and hear the carrier up to 100m away.


===

The Chemist.
I wondered into my local chemist and asked for some borax. I've bought plenty of borax from chemists in the past 25 years and never had a problem.
The assistant approached the dias upon which the chemist was perched.
He looked down upon me and decended from his lofty postion to interigate me.
Why do you want borax ?

Shit ! How do I explain this ? Ok, he's a smart guy, he might understand.
"I'm making a negative resistance semiconductor using a glass of water !"
Do you know the Doc from "Back to the Future" ? Yeah, well that's the look I got from the chemist who immediately decided that a 'negative whatever' was some sort explosive.
I don't know what it is your trying to do but it sounds as bad as asking for Iodine.

At this point, my view of the chemist as being the smarter person changed.
I pointed to the tincture of iodine the nearby shelf and to a cleaner which I knew would have 'ammonium hydroxide' and told the chemist that if I was going to ask for material to make explosives, I would not ask him directly for those materials and instead would purchase the tincture of iodine and refine it without his knowledge.
It was about then he suggested I leave.

BigW next door had Borax in the garden shop.
I wonder if he called the terrorist hotline ?

best4less

When I go to a new chemists to pick up the Bosses medicines I cant help but
ask if my 4 litre bottle of Sudoephedrine has arrived yet LOL
One day I'll get one

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trash

Different Chemist....
I went in to find Sudafed. All I could find on the shelves was that substitute rubbish.
I went over to the counter and demanded the snotty nosed brat give me the real fvcking pseudoephedrine !
He pulled out the real Sudafed from behind the counter... I inspected the box and told him, "What's this shit ? Pseudoephedrine hydrochloride, do I like look a bikie ? Give me the real stuff pseudoephedrine sulphate !"
Once again, the chemist was forced to come down from his altar to consult me.

z80

Trash....you have too much time on your hands if you are assaulting the local chemist...

Maybe we need another thread about how to remove a tree stump..the "quick" way?




( I think mod Fernbay is asleep tonight if you want to run the gauntlet )






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bcurko

To z80 if you read my first post you would quite clearly understand that i didn't think this subject was going to be a walk in the park bludge without requiring some decent effort. But you seem to like stating that i jumped into the subject thinking that it was just a 1+1 subject.

I cannot choose the way my mentor teaches me and how he chooses to not grasp how i am struggling with the topic. What do you want me do it's not easy for everyone

But a mate in my class told me what we were building (A Stable 555 circuit which should flash for 11 seconds and then time out and stop. This is the circuit as it's currently not working. I am still trying to classify what the problem is..

Sorry for the poor quality images my N95 autofocus seems to be not focusing correctly... loving it too..

z80

I don't know the background, but you have jumped into something quite advanced, a lot of concepts are required before you can put in "a decent effort".


If all is as you say it is, then your mentor is a fool.
No-one can start to understand an astable multivibrator circuit without knowing what an ohm or a farad or time constants are.

Please be sure to show your mentor this post.



What class is that? Year 11?

You have no hope in hell of classifying what the problem is if you don't understand how time constants work.

I am sorry to he so harsh...but it is quite unrealistic to expect you to "fix it" without all the fundamantel concepts.

(unless it was meant as a paint by numbers exercise and you mixed up the paint...or the numbers )



Oh...just by loking at the components in that blurry photo i can tell that the circuit doesn't contain enough "bits" to work as a one shot AND an astable.




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beer4life

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z80

I guess the VR and yellow cap may be on the reset line, and just noticed the missing resistor in the blurry corner.


My money is on the two caps being mixed up.

I'm surprised the mentor didn't use a Pic chip....hell we all know they're a piece of piss.

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FTO King

Google KVL , KCL, OHM'S LAW, VOLTAGE DIVIDER RULE, CAPACITANCE AND INDUCTANCE.

And ill give you a heads up if you wanna know what the 555 chip does it has a flip flop in it (google it).

Because ima uni student myself and i know the pressurs of schooling/uni i do feel sorry for you for failing an exam but i want to see you at least try first.When is it due in?if all else fails ill lend you more help.

beer4life

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trash

Bcurko .... try and find your local Tandy store. They 'may' still have their 555 engineering book. It will cost you $5 and is the shortcut you seek.

You should also consider teaching yourself ohms law, DC theory and AC theory. This will be enough to help you scrap through. Those three subjects can be learned in about 3 days on your own, quicker if you have a good teacher.

z80

Hmmm.....that's quite an accelerated learning curve Professor.


I guess as long as we don't let him touch anything after the three days all should be good to go...

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