Thread: 555 timer plz help

hi ppl,
must start of by saying this is a fantastic site and full of helpfull info in all sorts of tehc areas, wondering if anyone can help me with something.

I recently put together a TLC555 CMOS 555 TIMER along with a few resistors capacitors and a npn switch transistor and installed it into my videogame controller, in order to give me the ability to tap a specific button rapidly (aka rapid fire or turbo button). It works perfectly also put a led to display the speed.
I now wish to make it adjustable so that i have three speeds to choose from , does anyone have that tehc know how to push me in the right direction of doing so?
Any help or suggestions greatly appreciated, oh and sorry about my terrible spelling although i might of done ok.

thanx once again great site

You can put a variable resistor (pot) in place one of the resistors ( the one that connects to pins 2, 6). Or you can put a 3 position toggle switch and a few resistors there. Depends on how you want it to be set up.

You should be able to get a miniature variable resistor (pot); connect the wiper to pin 6, and one of the outside pins to pin 7. remove the 56k resistor. If you use a 100K pot, you'll be able to adjust the speed from half the current speed to impossibly fast (the controller will ignore it).

thanx dougy ill give it a go and let you know how i went, once again thanx for your input

i tried what you sugested and it works there are two or three different speeds i can shoot at b4 i turn it to high and the controller dosnt respond , you know your shit dougy thanx alot , but it seems to not function properly at the start the first few time i press it it fires a shot then it reloads this happens 2 or 3 times then and then it works fine do you know why this might be happening,

also forgot to include the i also have a small led light that goes from - on the led to 3 on the timer and + on the led to a switch that goes to + on the battery
once again thanx for your help

Wow, you managed to fit all those words into a single sentence! So what are the problems?
* If you turn the repeat rate too high the controller ignores it? That's to be expected. Just don't turn the speed up so high (or you can put a resistor in-line with the pot to limit the maximum speed)
* Sporadic operation at the start? Not sure. :clutching straws: Maybe a loose connection or you need to connect a capacitor across the 555 power supply.

Also, make sure the LED has a resistor (say, 470R for a 5V supply) in line with it.

if you connect the battery to the 555 circuit you might be getting power glitches.
look at this site for suggestions

LM555 Timer Circuits

hope this helps