Need help identifying these symbols and what they do

[jsean21]

What do all these symbols do? so confusing

I am doing a project for GCSE creating a circuit board. i dont know what these things mean and what they do. Please help, thanks.
-[2k2]- thats one, what is it and what does it do?
-[270k]- dont know what this is either and what it does
-[100k]- same with this

they look like that except they got a box around the writing, please can someone tell me what each does and what affect they could have on a circuit.
Thank you

 

[fingaz]

I am doing a project for GCSE creating a circuit board. i dont know what these things mean and what they do. Please help, thanks.
-[2k2]- thats one, what is it and what does it do?
-[270k]- dont know what this is either and what it does
-[100k]- same with this

they look like that except they got a box around the writing, please can someone tell me what each does and what affect they could have on a circuit.
Thank you

Hi,

These are all resistors. the numbers inside are the resistance. eg 2k2 =2200 ohms. (2.2k but people tend to put in the k where the decimal point is -> 2k2)
270k = 270,000 ohms
100k = 100,000 ohms

Hope this explains it for you

Neil

 

[jsean21]

thanks that helps but what is a:
-[270R]-
is that just another resistor aswell or a 270 ohm variable resistor?

 

[fingaz]

thanks that helps but what is a:
-[270R]-
is that just another resistor aswell or a 270 ohm variable resistor?

It depends on the circuit diagram. can you post it, or post a link to it?
Or try looking on goole for citcuit symbols. The symbol for a variable resistor is the same as the symbol for resistor, but it has a '3rd' leg, which is shown on the diagram as an arrow pointing to the middle of the resistor.

Just googled circuit symbols and got this link for you : Circuit Symbols of Electronic Components

Have a look over these, print them out to make it easier to look them up.

Neil

 

[jsean21]

heres the circuit diagram i have to construct but i dont know how it works and what components do what:

 

[Nigel Goodwin]

270R is 270 ohms.

 

[jsean21]

cool, but know i know what everything is what do they all do,im still confused.Please can anyone help?
thnak you

 

[fingaz]

Ok,

100k is a Variable Resistor, it's resistance can be altered by turning the shaft. It's resistance can be anything from 0 ohms to 100K ohms depending on the position of the shaft.

The symbol below that is a Light Dependant Resistor (LDR). It's resistance will vary depending on how much light (or dark) it is exposed to.

Look here for a better explanation : Light Dependent Resistors

The BC108 is a transistor, in this circuit it is used as a switch.

The link above actually uses a circuit similar to the one you have (but it has 2 transistors connected as a 'darlington pair', don't worry about that)

You also have a 220R resistor (220 ohms, some people tend to write R instead of ohms)
You also have an LED (Light Emitting Diode)

The link to the website above should tell you what the circuit does.

Neil

 

[jsean21]

Thanks thats brilliant, just what i needed, one other thing the resistors in the circuit are in place to just limit the amount of current flowing to the next component right?
sorry for keeping on hasseling you, but this is something i really need to get my head around

 

[fingaz]

Thanks thats brilliant, just what i needed, one other thing the resistors in the circuit are in place to just limit the amount of current flowing to the next component right?
sorry for keeping on hasseling you, but this is something i really need to get my head around

Right (for this circuit), except for the variable Resistor. The purpose of the VARIABLE resistor is to set the sensitivity of the circuit (ie, to alter the amount of light needed to turn on the LED)

 

[jsean21]

Thanks thats very helpful

 

[fingaz]

No Problem,

Just one tip, You can get loads of information from Google Quite often it will come up with links that are aimed at 'newbies' so you may get an explanation that is easier to understand.

 

[Hero999]

Do you know the coloour code for resistors?
Resistor - Wikipedia, the free encyclopedia

And that there is a set of standard values for resistors and capacitors?
Preferred number - Wikipedia, the free encyclopedia

You can't go out and buy an 800R resistor, not easilly anyway (some non-standard values are made but they tend to be more expensive) you'd normally use an 820R resistor.

 

[Noodles141]

Whats this for out of interest?

 

[4pyros]

Whats this for out of interest?

I am doing a project for GCSE creating a circuit board.

This thread is vary old.
The OP has not posted sense 2008.

 

[dougy83]

Whats this for out of interest?

Looks like a primitive 'night-light' type circuit (i.e. LED turns on when it's dark)