[sdiy] flashing LED?? blinking led FLED (are they internally similar to a UJT?)
Roman Sowa
modular at go2.pl
Wed Jun 12 09:36:45 CEST 2024
Flashing LEDs were very popular in the 90's. People used to put them in
their cars as fake car-steal alarm. Soon it became the symbol of bad
taste in electronic design. Way before blue LEDs took over that.
A few years ago one of tech magazines for kids published flashing
christmass tree project using one flashing LED as a timing device. It
contained all the parts and cardboard with printed christmas tree where
you put all the parts. Conections were printed at the back side.
Basicaly the flashing LED takes much more curent when it shines, and
that current was controlling one chaion of regular LEDs, while the other
chain was driven from transistor inverter also controlled by fLED's current.
I still have it...
Roman
W dniu 2024-06-11 o 16:57, loss via Synth-diy pisze:
> I am building a small motor based "BUG" robot with my son. One of the
> parts the project calls for i have never seen before..a flashing led or fLED
>
> The text says that if you use a regular led the motor will not work
> properly (it must somehow be using the FLED as a timer which allows
> current to flow from the storage capacitors
> to the motor. The text gives no further explanation but it does
> reference it as a timing element. Later projects use a hard to obtain
> part called the 1381 trigger but i would rather use parts I have on hand.
>
>
>
> Obviously I could order an FLED but as the datasheets are very sparse I
> was wondering if anyone has any idea internally how these parts work.
> Where does the timing mechanism come from?
> I was wondering if even though they are a two leg device..that
> internally they may have similarities with PUT or UJTS. I have a whole
> bunch of PUTS around.
>
> thanks!
>
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