9 LED's chaser with reverse using 4017

[justDIY]

I think that makes sense about the ORing... since you want leds 2-8 to blink 'twice' but 1 and 9 to only blink once in the sequence.

I haven't heard of multisim before.   I've used PSpice (way to complex for my needs) and currently use Cadsoft Eagle.

from the same 'sim', I take it that program allows you to simulate the circuits?

[cpemma]

Can I use the diagram on this site under "10 Channel LED Sequencer":
http://ourworld.compuserve.com/homepages/Bill_Bowden/page5.htm#4017-7.gif
for the transistors and LED's?

Will it work with no resistors on the transistors bases? Won't they burn to death?

The circuit has the boost transistors in emitter-follower config, so the voltage to the led & resistor is the voltage at the base (equal to the 4017 output voltage, which will be a bit below the supply voltage) less about 0.6V.

The base current is automatically set to load current/transistor gain, so providing you don't short out the load, you don't need base resistors; a base resistor will in fact drop some volts (base current x resistance) and reduce the output voltage even more.

See here for more detail.

To keep construction simpler, I think I'd connect the transistors in a switch configuration, using a few ULN2803, a cheap and common octal darlington chip with built-in base resistors.  I 18-pin chip will drive 8 leds, neater than 8 transistors & 8 resistors.

[Rob]

emitter-follower

Good catch.

[Anotherledmember]

I will not pay ANYTHING for this ciruit!
I would NEVER have bought an IC for 3.00 !!
It did'nt cost me anything to get all my 5 4017-ic's! 
I only use old components that I find on old ciruit-boards!
I have also found the LED's!
You would'nt die because you have to make a few more solderpoints!!!!!

ooh k.   I saw "can anyone help me" and just tried to show other ways.  I get IC's free and LEDs dirt cheap but thats besides the point.  Not just your led situation, but just informing how this can be done.  I did all that discrete and linear circuits long ago.  Like I said before, its necesary for a good foundation.

    16 LED Video  
Light Saber

[Mr. Diode]

 
 

I have found an IC called ULN2803A. Can it bee used in ths ciruit?


See attached datasheet for the ULN2803A. 

 

[Anotherledmember]

Any luck?

[justDIY]

I have found an IC called ULN2803A. Can it bee used in ths ciruit?

about the only thing this chip is good for would be eliminating the need for discrete drive-transistors, in regards to switching LED arrays or incandescent lights.

a darlington pair is two transistors linked so a very small signal can switch a very large signal ... personally, I'd use a logic-level mosfet for this, but I'm sure the darlington pair offers some advantage in some situation.

[Anotherledmember]

No luck yet i see.

[cadstarsucks]

I have found an IC called ULN2803A. Can it bee used in ths ciruit?

about the only thing this chip is good for would be eliminating the need for discrete drive-transistors, in regards to switching LED arrays or incandescent lights.

a darlington pair is two transistors linked so a very small signal can switch a very large signal ... personally, I'd use a logic-level mosfet for this, but I'm sure the darlington pair offers some advantage in some situation.

Actually the 2803 is very good for diving say 28V from 3V.  As for me, I would just hang the decoder, which you need anyhow, off the high rail to drive FETs.  A common base/gate circuit does level shifting nicely.

Dan

[cpemma]

Can I use the diagram on this site under "10 Channel LED Sequencer":
http://ourworld.compuserve.com/homepages/Bill_Bowden/page5.htm#4017-7.gif
for the transistors and LED's?

Will it work with no resistors on the transistors bases? Won't they burn to death?

A bit late answering, but it might reassure someone someday ... each LED (and the LED resistor) is on the transistor's emitter side, so base current is automatically limited to LED current/Transistor gain.  The transistor is not being used as a 'switch' but as a 'voltage follower'.