bcurko

Hey guys I'm currently doing practical electronics at my school as an elective. I am really struggling to understand the flow of electrons and the whole idea with capacitors and the such... My teacher is compelled to think that i know most of the work and that well im a genius

So anywho the circuit I'm building is a Led Timer with 555 Timer it's basically meant to be able to flash a certain amount of times per second and the variable resistor is their to control the flow so that i can control the speed.

This is similar to what I'm building just that i have changed some resistors and such....


What can you guys suggest i do ? Are there any books that can help me

Thanks Heaps and no this isn't a hwk related question it's work that I'm struggling to understand...

Thanks Curko

Fernbay

Cap's pass AC & block DC.

Low freq's need bigger caps, & higher freq's need smaller ones.

if the cap had bulged, the plastic label split or pulled down, top rounded, blacked, burned etc, then it needs changing


If your trying to learn current flow, then use a passive circuit, maybe a few transistor/diodes etc, but avoid IC's etc. We just treat them as black boxes & accept that they work, & if they don't, we change them

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bcurko

Yeh thanks for the reply it helps to know that someone is here to help. But the only flaw in your reply is that if i modify my circuit including diodes or transistors my teacher will fail my practical work as it doesn't follow the classes curriculum. although i could try ....

Fernbay

You could also build it on a breadboard & meter the current, as long as the ac parts are low frequency

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rievax

It seems like you should be building this circuit.


Replace R2 with a variable resistor.

beer4life

G'Day Curko,
You sure like to jump in at the deep end.
Try a google search " 555 timer circuits ".
Amongst them you will find this one.
555 Timer/Oscillator Tutorial
Seems as good as any of them. Details history and operation far better than I can explain in a few short words.
I dare say that various versions and applications of these devices are more prolific than grains of sand on Manly Beaches.

Kindest Regards, " The Druid ".

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Studio1

Better to put a variable resistor in series with R2 as you don't want R2 to equal zero ohms (dead short) at any point.

As for assistance with learning electronics, do you have a local electronics club or Ham Radio club? They would be a good start to help you. As a kid I joined an electronics club that was run by the local Ham Radio people. I learnt a lot at that place and have great memories of my times there on a Friday night.

In fact, I still have the very first PCB I ever made from there - an astable multivibrator using 2 transistors to switch two LEDs as flashing "railway crossing" lamps.

While you are here, take a look at this page: Welcome to Play-Hookey!

Some very good stuff on there that might help you with electronics.

Joey

If you multiply the resistance by capacitance you will get the frequency in milliseconds, , the charge or discharge time remain constant.

EG: if you pick a 1uf cap for C1 and 100 Ohm resistor for R1 it will be 100 x 1 = 100ms meaning your output will flash 10 times per second.

So if you want it to flash once per second you change R1 to 1K or 1000 ohms.

If you were to put a wire link across R1 you would need a 1000uf cap to get the same 1 second pulse.
But if you added a 1K resistor using the same cap it would be 1000 x 1000 about 16.6 minutes per pulse. this is where these IC's become good timers.

Basically if you use a 1uf cap for C1 and a 5K variable resistor ( pot ) for R1 you will be able to play quite a bit with frequencies that are visible via a led on the output.

best4less

Now even I can understand that
Very nicely worded

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iwacelect

ARRRGGHH, warms the cockells of me hearrt hearing 'bout time constants


arrrgghh


dont forget 5 x tc = finished! on a diminishing one off pulse that is!

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trash

Looks like the guys above have got the 555 time theory covered. But maybe you need a little help with the ultra basics.

For anybody having trouble with electronics, there is one easy way to understand components and how they work. Every component has a mechanical equivalent. A friend who is a very good mechanic picks up circuit theory when I describe a component to him in mechanical terms.

Capacitors are like springs.
If you stretch a spring it stores energy, when you let it go, the potential energy discharges as kinetic energy.

An Inductor works like a flywheel.
A flywheel stores kinetic energy. A flywheel likes to remain at a constant velocity, any attempt to change that velocity is met with a resistance (or reactance). An inductor attempts to maintain a constant current.


Another example is to think of a capacitor as a water tank.
This time the resistor is like a tap which allows water to flow in.
The lower the resistance (tap open) the faster water flows into and out of the tank. The amount of water flowing through the pipe is the current. The volume of the tank is the capacity, the level of the water in the tank is the voltage and the amount of water the charge.

The 555 timer works a bit like the tank float in an automatic toilet.
The toilet tank fills slowly according to the tap setting (the resistor)
When the tank reaches a certain level, the valve opens, the toilet flushes. Another tap controls how fast the tank drains, (either a second resistor or the same resistor).
Finally when the tank is drained, the float opens the fill valve and the tank starts to fill again.

So the time it takes for the tank to fill and empty is controlled by two varibles. The setting of the taps, AND the size of the tank. If the tank is small, if fills quickly. If it is large, it fills slowly.

The time it takes for the cycle to complete is the frequency.

The dunny, like the 555 timer can be made to operate in many different ways.
A standard toilet charges and waits for a trigger (pull the chain) and then refills.

oyama

well done joey & Trash, i learnt something too

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best4less

You guys should be teachers very well done,I would even pass in your class

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Joey

hehe talk about getting back to basics , Priceless trash

Studio1

What does a non-standard dunny do?

iwacelect

well covered trash, another way is to think of all electronic functions as hydrolics... resisitor = tap/restrictor, capacitor = pressure diaphram, volts = pressure, amps = litres/pm...

after all a computational device can be powered by water

Water computer - Uncyclopedia, the content-free encyclopedia

Water integrator - Wikipedia, the free encyclopedia

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trash

Thanks guys,
yeah I'd love to get into science education. I did a little with the CSIRO's Double Helix club many years ago. I have to pay my debt back to society thanks to Rob and Dean from the Curiosity Show. Those guys are my inspiration.

One of the guys I occasionally work with heckling me about comparing a 555 chip to a toilet. I told him to wait for the sequel, the 556 dual flush !

Joey

Oh man that was my inspiration aswell , Loved that show !!

As for the Dual Flush , couldn't you make that more interesting in multivibrator mode

bcurko

Hey guys guess its time for me to start moving. I really want to pass electronics for my sake and to please my parents but i really do need another method to teach me whether it be from the For Dummies Book for Electronics whatever works! i just need to get this from a to b. Im currently ranked 1st in the class due to my assignment being perfect but that will change as i failed my exam for electronics and am behind my prac work by an odd 6 weeks which isn't good. '
So can someone please help me this is a dire situation

bulbous

Turn the music off, close the web porn browsers and do some work !

YOU have to do the work, WE have already done it. You "guess it's time for me to start moving" ....well, WTF have you been doing ? Your assignment might have been "perfect" but it was essentially done for you ! YOU have to think, study, make notes and remember things for exams - nobody is going to - or can - do it for you.

If you have specific questions people will gladly answer them, but YOU have to make a start to be in a position to ask relevant questions.

This all might sound tough, nasty or grumpy - but sorry mate, it's the facts ! .