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LED Flasher

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daviddoria

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**broken link removed**

(sorry for the banned website)

this doesn't seem too difficult... however i am having little success. I am using components roughly what they called for... it doesn't have to be exact does it? like instead of 330ohms i used like 300ohms and instead of 10uF i used around 20.

if that matters i can get more accurate components, but what else could be wrong (i would give more information, but i see nothing to tell you except the lights dont flash! haha)

any info would be great
thanks
david
 

Pilot

New Member
Re: schematic questions

daviddoria said:
http://www.*****************.com/lightsimages/1.gif

first thing, what is the difference between NE555 and LM555 and the rest of the 555s?

Different manufactuters use different prefixes. Some are made to a different spec ie. Military, low power cmos. Get a copy of the 555 data sheet - available on the web.

1) on that diagram, where is the negative terminal of the battery?

Under the 0.01uF capacitor. That bit that looks like an upsidedown T is an earth/ground designator.

2) on the 100k preset resistor on the left, what is the line from the dot below it to the middle of it?

The resistance of a variable/preset is measured across the two outer pins. The centre pin is connected to a slider that allows you to vary the resistance between zero and maximum. To test it connect an ohmmeter across two of the pins and adjust the preset. If the value changes then one of the connections is on the slider.

3) what is the line all by itself at the very bottom?

This just shows an alternative arrangement for connecting the LED. Read te text that goes with the diagram.

i'm sure these are silly questions, but i'm just trying to make sure my timer works before i use it in a bigger project, so i thought this would be an easy way to test it

thanks
david
 

mechie

New Member
555 Timers

(Your link will not display as it is a banned website !)
A bog-standard 555 astable circuit
Question 0 (!)
All 555 ICs are basically the same, the letters at the front are usually just a code to say who made them. The only exception to this I can think of is the 7555 which uses CMOS technology and therefore may not work the same in all circuits.

Question 1
See Question 3 ! That line (connected to pin 1 of the 555) is the neg terminal.

Question 2
The 100k preset has 3 terminals, one to each end of its carbon track (a fixed 100k resistance in this case) and a third, the wiper, which, by rotating the centre bit of the preset, will vary from one end (a near short to one fixed terminal - 100k to the other) through centre (about 50k to either fixed terminal) to the other end (100k to one fixed terminal, a near short to the other). Wow !
This circuit only needs a variable resistor (either fixed terminal and the wiper), so just to be tidy they have connected the 'unused' fixed terminal to the wiper. This makes little difference to the operation of the circuit, it's just good practice.
The 'dot' you refer to is just this junction or connection.

.
 

daviddoria

New Member
why is that a banned website?

can i just put a normal ceramic 100k resistor instead of that wiper thing or whatever you were talking about (hehe)?
 

windozeuser

Member
That Admin Warning Sucks He is immature

The Only Way U can get sued from copying other people's circuit's is that they have a copyright of the Schematic ( I THink)
 
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