LED Cube with K8055

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1

Hi im planning to build an Led Cube and I want to control it with my K8055.

Because im not satisfied with only 8 Leds flashing i want to Multiplex (or even Charlieplex) them…
So my main Question is how many Leds can I control with my Board?

Would it be 16 Led with Multiplex (8 by 8 grid) or less because I can’t seperate Aniod and Kathiode?

Can the board even Charlieplex them? Because for this it would be necessary to enable a TRI-State ( Input-High-Low)…
Like in http://www.youtube.com/watch?v=ECXk95qYZu8&feature=relmfu

Thanks for the help in advantage
Biohazard

2

Multiplexing is possible but Charlieplexing is not.
You may multiplex up to 16 LEDs.
Here an example how to multiplex 8 LEDs.

When the output O7 is not active (open) and O8 is active (pulled down) you can turn any of the LEDs D1 to D4 on.
When the output O8 is not active (open) and O7 is active (pulled down) you can turn any of the LEDs D5 to D8 on.

You may complete the circuit by connecting similar groups of LEDs to O5 and O6.

3

Thank you for the explanation. I was affraid i can damage the open collector Output channels when i create a direct connection like this. So there is no need for a Transistor?

4

You can’t damage the open collector if you use the circuit like in my previous post.

5

Hello folks!

Not a new thread, almost the same idea.

Of course, I can add some digital output channels by coupling up to 4 K8055,
but my idea was to use a demux like a DM54LS154J (4 to 16 demux) or a DM74LS138N (3 to 8 demux) which I have.
Including a TTL/CMOS Logic, because it’s in my case not a good idea that channel 8 is active when starting (booting a PC).

My Questions:
Can I connect the outputs of velleman’s K8055 (the ULN 2803) directly to the inputs of this LS or HCT type chips or do I need some resistors for current limits?
And do I need to use pull-up/down resistors?
Do I have to connect pin 10 of the ULN2803?

Thanks in advance for your time spent helping me.

6

[quote]Can I connect the outputs of velleman’s K8055 (the ULN 2803) directly to the inputs of this LS or HCT type chips or do I need some resistors for current limits?[/quote]You can connect the K8055 outputs directly to the TTL, LS or HCT type chip inputs.

[quote]And do I need to use pull-up/down resistors?[/quote]If you use TTL (or LS) then the circuit may work also without the pull-up resistors . For CMOS you need to use pull-up resistors (e.g.10k).

[quote]Do I have to connect pin 10 of the ULN2803?[/quote]No, this pin have to be connected for inductive load only.

7

Dank U wel voor het snelle beantwoorden! Thanks a lot!
I studied some electronic basics and now I understand PIN 10, Open Collector (TTL) and Open-Drain (CMOS). Pullup-resistors of 10 kohms seem to be a standard value which should work fine in almost all circuits with 5 V DC.