looking for 1 transitor led flasher circuit..that works!!!!!

[deadastronaut]

ive found a few, and breadboarded them...no joy..

i know theres 2 transistor ones out there..but im looking for the smallest one...anyone?..link/pic etc...

i tried this.with a 2n3904..but it just wont have it....

[R.G.]

I wouldn't expect that circuit to flash.

Two things come to mind.
1. Why not use an LED with an internal flashing circuit so you don't need *any* transistors at all. Yep, they exist.
2. In general, single transistors don't oscillate all that well. You can get a twin T to oscillate, but it's hard to get it to drive an LED, too. Use something like a 2N6027 PUT and you can get a relaxation oscillator to run with only two resistors and one cap, but driving the LED well is tricky. It works best in short, sharp spikes of light.

[deadastronaut]

I wouldn't expect that circuit to flash.

Two things come to mind.
1. Why not use an LED with an internal flashing circuit so you don't need *any* transistors at all. Yep, they exist.
2. In general, single transistors don't oscillate all that well. You can get a twin T to oscillate, but it's hard to get it to drive an LED, too. Use something like a 2N6027 PUT and you can get a relaxation oscillator to run with only two resistors and one cap, but driving the LED well is tricky. It works best in short, sharp spikes of light.

hi RG yeah ive got flashing leds already...but i want to be able to vary the rate......

ive tried various 2 tranny led flashers...but again i want minimal parts...and no ic etc...

ive also tried this one and it wont work...! even though the guy has a video/gif showing it working...

[CynicalMan]

I'm on my phone so I can't link it, but there's a one-transistor lfo in Tim Escobedo's Wobbletron with a flashing led.

Edit: Here's the link: http://folkurban.com/Site/Wobbletron-703.html

[deadastronaut]

I'm on my phone so I can't link it, but there's a one-transistor lfo in Tim Escobedo's Wobbletron with a flashing led.

thanks alex i'll look for it...

edit:
anyone see why the second schematic would or wouldnt work....like i said the guy had it working on his site...weird!!!...

shame coz its nice and simple too..

[Manny]

More super simple LED / LDR circuits on the way here Rob? 

[deadastronaut]

hmmm maybe!

like me....

[arma61]

this one works, I get it working long time ago, though, IIRC, it didn't work at 9V, again IIRC try to change the type of LED

A.

[deadastronaut]

cheers armando.

cool i'll give it another go then...i like the simplicity of it!...back to the breadboard!..

[twabelljr]

but again i want minimal parts...and no ic etc...

No IC huh? Craig Anderton's metronome project is a very simple 555 circuit (less than 10 parts) that uses a 10k pot to make a small speaker tick at 60-1500 bpm, 120-3000 bpm, or 30 to 750 bpm depending on a couple of cap values. I'm sure it could be made to safely flash an led but it uses an IC and I have no idea what you are up to.  

[deadastronaut]

but again i want minimal parts...and no ic etc...

No IC huh? Craig Anderton's metronome project is a very simple 555 circuit (less than 10 parts) that uses a 10k pot to make a small speaker tick at 60-1500 bpm, 120-3000 bpm, or 30 to 750 bpm depending on a couple of cap values. I'm sure it could be made to safely flash an led but it uses an IC and I have no idea what you are up to.  

yep i can do it with 555's etc...done that ages ago...i did it with 2 trannies too...but im after the worlds simplest variable speed flasher now!...to experiment with in a very small project!.....!!!!

the 555's are prone to clicking issues...so am trying to avoid them......

[arma61]

Hi

digget out from the bin this little thing, still works!! and I didn't remember correctly, it works at 9V and if you put a "sag pot" at +9 it acts as a speed control

here's a video of it "in action" !



very nice to simulate an antitheft system on motorbike!!


Cheers m8s
Armando

[deadastronaut]

cool...(that is the oene above isnt it?)..on 9v  yay!!!!!!!............havent got mine working though!..

will this work on a 2n3904....or other npn...

it says 2n2222...what alternative could i use???any ideas!..

cheers rob.

[twabelljr]

the 555's are prone to clicking issues...so am trying to avoid them......  

Gotcha. Looks like Armando might have a solution. Keep experimenting. Your posts are great to read. I'm a breadboard guy too.

[deadastronaut]

the 555's are prone to clicking issues...so am trying to avoid them......  

Gotcha. Looks like Armando might have a solution. Keep experimenting. Your posts are great to read. I'm a breadboard guy too.

cheers tommy. yeah i love experimenting on the old breadboard!...i'm getting done over by a tiny simple circuit though!..arghhhhhhhhhhhhhhhhhhhhhhh...


edit:

alternatives to a 2n2222 anyone?...

[arma61]

Yes Rob, video is related to the Dick Cappel's circuit

Had a look at it again and also put it again on the breadboard, some info

- works on 9V
- I didn't use the 2 resistors
- my cap is 470uF
- seems only 2N2222 works, no 2N3904,BCs, 2N50.. (sorry Rob, looks like you need a trip to Craplin  )

- the sag pot is the trick, without it the LED stays on all the time
that's true for my board, it's set up as follow

To recap  V+ to lug 1 of a 22k Linear pot (value not crucial i think), lug 2 of pot goes to T1 Emitter and Pos side of 470uF,  T1 Collector goes to Pos side of LED, Neg side of cap and LED go to GND

don't ask why i did these, it was almost 2 year ago, really I don't remember.. but it works!!


Armando

[deadastronaut]

Yes Rob, video is related to the Dick Cappel's circuit

Had a look at it again and also put it again on the breadboard, some info

- works on 9V
- I didn't use the 2 resistors
- my cap is 470uF
- seems only 2N2222 works, no 2N3904,BCs, 2N50.. (sorry Rob, looks like you need a trip to Craplin   )

- the sag pot is the trick, without it the LED stays on all the time
that's true for my board, it's set up as follow

To recap  V+ to lug 1 of a 22k Linear pot (value not crucial i think), lug 2 of pot goes to T1 Emitter and Pos side of 470uF,  T1 Collector goes to Pos side of LED, Neg side of cap and LED go to GND

don't ask why i did these, it was almost 2 year ago, really I don't remember.. but it works!!


Armando

brilliant...thanks for that armando..nice one!..even smaller then...yay!!!!!!!!!!!!!...excellent.

yep looks like craplins then ...hold on i can get 5 x2n2222's for a quid at bitsbox...i need solder too...so i'll order some tonight!..

does it give a steady pulse too..or does it get a bit random?...thanks a lot dude!.. rob.

[arma61]

Looks steady, I know, you can't see that in the video because I'm turning the pot continusly! but it really looks steady, that was the reason why I built it for my scooter, it just look like the LED alarm in the cars, "off time" just a little bit longer then the "on time", you kow what I mean ?

A.

[deadastronaut]

Looks steady, I know, you can't see that in the video because I'm turning the pot continusly! but it really looks steady, that was the reason why I built it for my scooter, it just look like the LED alarm in the cars, "off time" just a little bit longer then the "on time", you kow what I mean ?

A.

yep fake alarms..nice.  

yeah it sounds really good, and really tiny too!..just what i was looking for...for ages.....excellent..as long as i can adjust the rate im happy....cheers man...i'll update when i get it going...

i just cracked open my whisky... cheers amando!...


edit: so like this then!...gave me an excuse to try a schematic to pdf!......

http://dl.dropbox.com/u/7464107/simplest%20led%20flasher.pdf

[Manny]

Rob I've got some of those 2222A's from bitsbox.
If you want to hold fire I'll give this circuit a quick breadboard tonight when I get home form work.