Super simple oscillator

[mozly]

So I just started electronics and I'm a comeplete noob. I'm trying to build an oscillating circuit in which an led flashes. I wanna build this circuit using no ICs just components.

So far here is what I have: The problem with this circuit is that the led does not go dark again.**broken link removed**

ALL help and suggestions are welcome

 

[colin55]

Who said the circuit works? Where did you get it from?
Why don't you build a circuit that DOES work:
**broken link removed**

 

[Roff]

Try raising the value of the 470k to 1Meg or more. You might want to add a small value resistor (47 ohms?) in series with the cap to limit the peak current.

BTW, your transistor part numbers were swapped.

 

[colin55]

The circuit above is a particularly bad design.
Here is an improved version:


Even with these improvements, the circuit is not a good design.
The circuit is very critical to supply voltage. It will not work at 4.5v and does not work at 9v.
The flash rate is very low at 9 seconds for 22u and 4 seconds for 10u.
However the current is less than 20uA and does not alter when the LED flashes. The energy from the electrolytic is passed to the LED with no load-resistor wastage.

 

[mozly]

thx for all the Help. But, I tried both schematics with the correct parts yet the led does not oscillate, it merely turns on.

 

[colin55]

You are connecting the transistors around the wrong way. The second circuit must be 6v supply.

 

[mozly]

can the first one work with 9v?

 

[colin55]

The first one doesn't work at all. To make the second one work on 9v, change the 470k base resistor to 220k.

 

[mozly]

Also, Since were on the topic, are there any good books or tutorials for teaching circuits for begginers?

 

[colin55]

There's aren't, that's why I have produced various topics on my website. Just to describe one type of oscillator would require 400 pages. That's how complex electronics is.

 

[mozly]

How did you learn then?

 

[colin55]

By building hundreds and hundreds of circuits.

I have employed a number of people and even though they did not have University qualifications, they had all built dozens and dozens of circuits relating to their field of expertise.
Then a University person came along and wanted to write for my magazine. I said I would give him the parts for the project and he could build a prototype. "Oh, I don't do soldering." was his reply.
He wasn't hired.
Then another University person came along and I hired him. After 2 weeks he had designed the PC board and had it made. He then asked me to purchase the components.
He fitted them and all the wiring was back-to-font and the displays were all reverse.
When he made the board (It was hand made with tape in 1984) he didn’t realise he had to think of the track-work in reverse.
He didn’t show up the next day.
This is just to prove that the most important thing is to build things and not just “think” they will work.

 

[mozly]

Wow, thx for the advice. I would love to check out your website and magazine if you send me a link.

Also, that is the very reason I decided to try and learn electronics on my on time. I went over my physics text book's chapters on electricity and magnetism. It consists of nothing but theory about the laws of electricity and magnetism. I absolutely hate that all we do in school is theoy and theory is crap without any application. (btw I'm in college). I have seen tons people who are amazing at theory and crap at application. Thats why when I work on a physics project I never pair up with a theoretical genius; they are all talk and no work.
My point is that school can't teach me what I want to learn so I should just do it myself.

This brings me back to my previous post. The reason I was asking for books and tutorials is that I need some way to start. I can't just build circuits without first getting some momentum going.

 

[colin55]

The address of the SITE is:

https://www.talkingelectronics.com

 

[mozly]

Oh ****!!!!!!! I built the circuit by replacing the resistor. You are Awesome man! thx

 

[mozly]

I did some modifications to the capacitor and the resistor in series with it and I can get oscillations in the 10000hz range with a mini loudspeaker