LED Chaser Circuit --Need Help

[Tony Stewart]

Hi spec et al, I have not used 74AHCxx but I see they are faster and slightly slower ESR and of course this is depends on Vdd. , worst case, best and typ vs temp.

But at room temp 4.5V Zol = 50 Ohms and at 3V Zol= 100 Ohms by design with Zoh slightly higher.

This Zol is voltage rise with rated current for Vol and voltage drop from Vdd for test current for Zoh

As consistent with all 50 to 70 CMOS families since the early CD3xxx days Zout drops as the Vdd max drops which means more current for "Advanced " meaning designed for lower voltages" Of course Zout increases with Vdd but so does self heating at f max.

The lowest Zout I have seen is ARM's "ALC2xxx" type with 22 Ohms. Each newer generation of CMOS uses smaller lithography, lower Vdd range, lower RdsOn and lower dynamic current with faster speed giving lower Pd at same f for dynamic losses and lower pF input capacitance.

The dynamic losses are due to RdsOn * C load*f^2 for RC rise time and f transitions per second since f is linear but power is I^2ESR or RdsOn

 

[ChrisP58]

I fully understand the interest in learning electronics by choosing a fully hardware solution. But if you're open to alternatives...

My choice to make a 5 led chaser in the minimum space, would be to use a small microcontroller. The PIC12F508 would do the job nicely. It's in an 8 pin package the same size as the 555. No other IC required. And fewer passive components.

https://ww1.microchip.com/downloads/en/DeviceDoc/41236E.pdf

 

[spec]

I fully understand the interest in learning electronics by choosing a fully hardware solution. But if you're open to alternatives...

My choice to make a 5 led chaser in the minimum space, would be to use a small microcontroller. The PIC12F508 would do the job nicely. It's in an 8 pin package the same size as the 555. No other IC required. And fewer passive components.

https://ww1.microchip.com/downloads/en/DeviceDoc/41236E.pdf

Hi Chris

How would you physically drive 10 LEDs with an 8 pin controller chip without additional chips? As there are only 5 output lines if you multiplexed the LED drive that would only give a 2 by 3 matrix making a total of 6 LEDs. Perhaps a 16F05 would be a simpler approach?

UPDATE: just worked out how to drive 12 LEDs with just the 12F508 and two resistors, I think!

What facilities would you recommend to program the PIC12F508? I know this can be checked on the net but it is always better to get information direct from someone with hands-on.

I ask out of interest. Also, this approach may suit another application and I have zero experience with PICs.

spec

 

[ChrisP58]

spec,
In his original request, Jeez said he only needs 5 LEDs. My choice of an 8 pin part with 5 outputs just makes that count.
For 6 LEDs yes, I would still use the same uC and multipex a 2x3 array. Much more than that and I'd probably just go for a uC with more pins.
The PIC16F505 from the same datasheet has 11 output pins. It would drive 11 LEDs directly, or 30LEDs in 5x6 array.

Need help for my Chaser circuit

4)My final out put will not have 10 LEDS , instead will have 5 LED's , is it best to use IC 4017? or do you guys have any other IC in mind .

Thanks
GJ