Hi folks,
This is my first post on AAC but I am not sure if this question is in the correct section (apologies if it isn't) and I am hoping I will get the answer I need.

I am quite new to the world of electronics and especially schematics. I have built a 4x4x4 RGB cube that I found on Instructables but everything had been done for me, even the Arduino code.
Now I want to design my own pcb for an 8x8x8 RGB cube based on the now infamous Kevin Darrah's cube, but I don't much like the idea of 192 transistors and 704 resistors to drive the led's.
I know that I can use the ULN2803 instead of the 2N3904s and resistor networks instead of the 704 resistors.
The programs I want to use to design the pcb are old but pretty easy to use, LiveWire and PCBWiz (unless anyone can suggest another easy to use pcb design program). I have thought about using EagleCAD or Fritzing but they are both a bit much for my limited pcb and pc knowledge, and I can't find all the parts I need in either of their parts databases.

My questions are >- How do I connect the SN 74HC595 symbol (with 8 output lines) to the ULN2803 symbol (with 1 input line) on a schematic,

and where do I connect the 8 outputs, the GND and Common +V with only 2 lines remaining ?
This is probably the most important piece of info I need and my 2 days searching have come to nothing.

Please help in any way if you can, all info will be looked into and will be gratefully received.
Thanks, in advance, to all who reply.

 

Welcome to AAC.

I'll let someone else answer your schematic software question, instead let me suggest you take a look at a TPIC6B595 which combines the function of the 74HC595 with a ULN2803 - it is a high power version of the 74HC595. I haven't had time to determine if this is a drop-in replacement to the other two IC's, so review the datasheet beforehand, but at a quick glance, it looks like a pretty good match. Good luck.

 

The 595 has 8 outputs, all in one schematic symbol. The 2803 has 8 independent sections, which can be shown all in one symbol like the 595 or as 8 individual symbols like you show. If you use the 8 separate symbols, be sure to include the pin numbers so you don't have duplicates by mistake. Line up the 8 2803 symbols to the right of the 595, and connect each 595 output to a different 2803 input.

ak

 

@elec_mech, thanks for your suggestion, it does sound like a good viable option to have both ICs in 1 package but I want to use the 595 and 2803 because I already have plenty of these and I already have quite a bit of Arduino code and annimations. Thank you for the reply though, it's good to feel welcome.

@AnalogKid, I think I understand what you mean in your reply, I have made another pic.

The first 4 inputs on the 2803 are connected as they should be according to the pin numbers, the second 4 are connected in the opposite way, LED to pin 10 common and 5v live to the output pin.
Strange thing is the second 4 LEDs seem to work in the simulation program. This I can't understand.

I think I might watch a few tutorials on EagleCAD or Fritzing and see if I can use one of these for my pcb.
This is much harder than I thought it would be.

Thanks again for your reply guys

 

The outputs load of the ULN2803 should be going to +DC not the DC common terminal, (or earth GND as you show it).

Max.

 

Physically I know how to connect them but the symbol of the IC is not available in the program I want to use.
The only symbol available for a ULN2803 is the one I posted. The lower pin on the symbol I posted is pin 10 and that is the common pin in all pinout docs I have seen. But the fact still remains that there is no pin 9 to ground the 2803 (the lower left pin on your pic).
I don't have time now to amend my pic but I will do so tomorrow to see if I can get any improvement on the simulator program I am using.

Thanks for your reply Max, in time I'm sure I will get there.

 

The Vcc and GND pins frequently are not shown on schematic symbols for IC's. Since almost everything has a ground pin that is well understood in the industry, eliminating them from schematics removes a lot of unnecessary clutter. Same for the power pins of digital logic ICs. The invisible pins are a part of the schematic symbol and are passed through to the pc board layout software in a file called the netlist. Usually you can open up a schematic symbol in some kind of editor to see what unconnected goodies are hiding.

ak

 

Hello Ant Brown
.
Well: The LiveWire simulator leaves much to be desired.
For example: Do not bring in their libraries SN74HC595; so only you inserted a socket and appointed him as such.
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Since this simulator brings separate internal Darlington, you have to insert more ULN2803 to complete the 8 that come in the package. -Insert Or copy and paste-.
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Analyzes the image which I attached. You observe how each NOT Darlington has different identification number and PIN also different.
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I attached also the file generated with the LiveWire simulator in .ZIP.
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.
.
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Hello ant247
.
If you are using the same simulator as Ant Brown or any other note what mentioned to you AnalogKiD.
Practically all simulators do not include the PIN's for the Vcc and GND digital symbols. Except some symbols in Multisim.
.
I recommend to You the simulator ISIS-ARES from Proteus Center Lab or Multisim from National Instruments.

I attached more information to study

 

Thanks for all your reply's, all info together makes it a lot more understandable for me now.
I think that having to put 8 darlington symbols together to produce 1 IC is a bit much, (I need to link 24 x 595 shift registers together) and that would make for a rather large schematic.
Would this work if I linked 24 of them together and put them on an Arduino ? (Ignore the voltage and resistor value, It's just the circuit that matters for now)


Thanks for all help so far, all is becoming useful in it's own way.

 

Although there is no harm in it, it is not really necessary to connect P10 for non-inductive loads.
Max.

 

Your LEDs are in the wrong orientation. Take a look at Max's example in post #5. The 'arrow' should point toward the ULN2803 pins (toward ground). We assume you're using common anode RGB LEDs. Common cathode (as you've drawn) won't work with a ULN2803.

 

Thanks for pointing that out elec_mech, I did say in my first post that I was quite new to electronics. Suppose it's a rookie mistake.
I have modified my pic again, is this now more like something that will work if I string 24 x 595's and 24 x 2803's together, with a few capacitors in for good measure (and 1 on every 595)

I am now a lot closer to my goal now than I was on Wednesday when I started this thread, BIG thanks to all you guys