Another LED sequencer question

[martinihenry]

Okay, I need to do this....

Cycle six LEDs on, about 1 per second in the bar-graph style...that is, the preceeding LED remains lit when the next one illuminates. When all six LEDs have lit up in turn, I need them to all simultaneously extinguish, and start the process over again.

I've seen loads of 'knight rider' type sequencers and bar graph circuits, but none that does this sort of "Old school neon sign" kind of sequencing.

I have no desire to use a pic or stamp. I know my request is easy to achieve via programming, but I have no desire to setup for that. I'd prefer to do it with standard ICs, like the 555, 4017, LM391x series and logic circuits.

Many thanks in advance for your thoughts!

Jason

 

[colin55]

Here is what you want:
**broken link removed**
**broken link removed**

 

[martinihenry]

Wow, that certainly looks like a good solution. Could an additional LED be added, as I need six separate LED cyclings? If so, what would that look like?
I'm trying to understand how the circuit works...the 555 is generating clock cycles, and I'm assuming the BC 547s are acting as switches to turn on the LEDs, but I'm not quite understanding how that occurs in sequence. I'm guessing it has something to do with the RC network and the two diodes?

Many thanks!
Jason

 

[colin55]

Just add another transistor-stage like the top transistor and a 10k resistor. The transistors come on separately due to the 0.6v drop across the base-emitter junction. This makes the LEDs come on individually.
The diode on pin 3 of the 555 allows the 100u to charge slowly via the 4k7 as it does not come into operation and discharge quickly when the output of the 555 is LOW as the diode come into operation.
The diode on the emitter of the lower transistor creates a 0.6v drop so that the output voltage of the 555 has to be a small amount before the first transistor is turned on.