Need Help

[colin55]

Here is a simple circuit using a PIC microcontroller. Any of the LEDs can be illuminated in any order at any time and any effect can be produced.
This circuit is a 3x4 multiplex. A similar circuit can be produced using CharliePlexing.

 

[Mr RB]

Here is a simple circuit using a PIC microcontroller. Any of the LEDs can be illuminated in any order at any time and any effect can be produced.
This circuit is a 3x4 multiplex. A similar circuit can be produced using CharliePlexing.

Actually your circuit IS charlieplexed Colin!

It's just not obvious on first glance that every 2 nodes has a inverse pair of LEDs between.

 

[Acetronics]

Hi,

I would simply use a 4029 UP/Down counter followed by a 4028 BCD to DEC decoder ... driving transistors to cope with Leds current ...

My little LED christmas tree ( 2 X 10 R + 10 G+ 10 Y leds ) is running with those for at least ... 20 Years.

the 4017 ( johnson counter ) is not bidirectionnal ... halas.

a µP is really overkill here ....

Alain

 

[caster.cp]

4028 will not do what he wants. It's a decoder. He wants a johnson counter, not a normal ring counter... I agree a ring counter would be much simpler, but...

And microprocessor nowadays are never overkill.

Budget for a uC solution
PIC 16F54 - $0.66
20Mhz Xtal - $0.12
LM7805 - $0.24

Budget for discrete solution
74HC299 - $0.68
74HC194 - $0.78
74HC14 - $0.47

(price of DIP parts at Digikey)

To make a really good and reliable discrete solution, he would have to spend more money as it would take more chips (I cannot see how he could do this with less than three ICs...)

Why insist on the discrete solution, so?
With one IC and less money you get a more reliable, more reproductible, easier to implement, easier to modify (while keeping the hardware the same) and smaller circuit.

I rarely tend to see microprocessors as overkill, since they are so incredibly cheap and easy to program... There's a plethora of PIC programmer circuits available on the web, that anyone with no knowledge on electronics could easily assemble.

 

[vne147]

I live in Seattle, WA. I would definitely be willing to work something out to have this done. Let me know if you are inerested and what we would be talking as far as price and we can definitely make this happen.

I sent you a private message.

 

[vne147]

Hi,

I would simply use a 4029 UP/Down counter followed by a 4028 BCD to DEC decoder ... driving transistors to cope with Leds current ...

My little LED christmas tree ( 2 X 10 R + 10 G+ 10 Y leds ) is running with those for at least ... 20 Years.

the 4017 ( johnson counter ) is not bidirectionnal ... halas.

a µP is really overkill here ....

Alain

I couldn't agree with caster.cp more. At first I thought the 4029 and 4028 solution would work but it wouldn't do what he wants. It could probably be made to work by adding some flip flops and/or additional logic but the µcontroller will be the cheapest, lowest part count, and easiest to add to or modify. I've already written the firmware. It took me all of 10 minutes.

 

[colin55]

The only real answer to this is a microcontroller.
No matter what you do with discrete chips, you will always find the client will want to change things.
In the end, the microcontroller will be one chip and an enormous amount of relief as anything can be changed and altered and modified and improved and extended as the client changes his mind over and over again.

 

[vne147]

Check your inbox. I sent you a PM.

 

[blueroomelectronics]

I would agree a microcontroller is a natural answer for LED sequencing.