Hi,
I've built this circuit:
formatting link
On a breadboard and I'm struggling to get it functioning correctly. The LED just stays on..
How can you tell if the 555 timer chip is working?
Fading LED circuit with 555 timer.. LED stays on..
Jul 16, 2010
3 Replies
led.html
Did you tie pin 4 to pin 8?
g-led.html
Actually, I think pin 4 (TTL) will float high if unterminated. It's a good idea to connect it high if not used, but should float high if unterminated.
-Bill
The fault may be the circuit design. If the BC547 has low gain then the circuit will never charge the cap to the required 2/3 supply voltage to make it change state. Try changing the 220 ohm resistor to 1k - 2.2k. Also in the original circuit substituting for the white LED with anything other than a blue will affect performance. With 2.2k it won't matter
Join the Discussion
Have something to add? Share your thoughts — no account required.
Didn't find your answer?
Ask the community — no account required