Power supply problems with 74HC595. 74HC165 and CD4051 chips

I'm building a digital modular synthesizer where I use a Teensy 3.1 for the control interface and each module has a 74HC595 and a 74HC165 shift register and a CD4051 multiplexer. Here are their datasheets:

74HC595 http://www.ti.com/lit/ds/symlink/cd74hc595.pdf 74HC165 http://grobotronics.com/images/datasheets/74HC165.pdf CD4051 http://grobotronics.com/images/datasheets/schs354a.pdf

I don't know much about electronics and I'm facing some issues which I think have to do with power supply. I've put 14 modules up to now and I'm using a voltage regulator giving 5V/3A http://grobotronics.com/voltage-regulator-lm1085it-5v.html which I feed with a 12V/2A DC power supply (that's what I have at home as I'm trying out different things). I've measured the current of the whole circuit with my multimeter and it said that it draws around 100mA, but again I'm really not sure if this is the case. The thing is that, with the said power supply, the circuit seems stable with up to 11 or 12 modules. After that I get some strange behaviour where some LEDs are dimly lit when they're supposed to be off and I receive some data in my computer which should not be there. Mind that I pass all data and power supply from one module to the next with ribbon cables like this http://grobotronics.com/ribbon-16wire-1m.html. I think that 3A cannot pass through such a thin cable, right? But still, I think that 3A are a bit too much for this circuit.

I'm powering the Teensy with a different power supply with common grounds.

Any advice as to how much current can these ICs draw and how I can overcome my issue will be greatly appreciated.

Try adding 0.1uF capacitors between power and ground at each IC. It's standard practice to use "bypass capacitors" on every IC.

Make sure you also have the recommended input & output capacitors on the regulator.

Also, check the voltage to make sure there is 5V at the chip... at the far-end of the ribbon cables.

I've measured the current of the whole circuit with my multimeter and it said that it draws around 100mA, but again I'm really not sure if this is the case....

...Any advice as to how much current can these ICs draw

100mA seems reasonable. You can check the datasheets for the chips and you'll have to calculate the current for the LEDs. Typically, each LED will draw around 10-20mA but that depends on the resistors you use.

I think that 3A cannot pass through such a thin cable, right? But still, I think that 3A are a bit too much for this circuit.

You said 100mA... The power supply does not "push" 3 Amps. The regulator puts-out a constant voltage (assuming it's operating properly and within its specified parameters, etc.). The current is determined by the load [u]Ohm's Law[/u].

Note that the LM1085 can only supply 3A under ideal conditions with the proper heatsink. With 12V applied and no heatsink, it will very-likely overheat and shut down (or shut-down partially) at less than 1 Amp.

Also with 2A out of your 12V supply, you can't get 3A out of the regulator. (The story is different with a switching regulator... Switching regulators are nearly 100% efficient so when you step-down the voltage, you can get more current out than you put in.)

alexandros301: I've measured the current of the whole circuit with my multimeter and it said that it draws around 100mA

If all you are powering is the 3 chips you listed, 100mA sounds a little bit high but reasonable. However, as your post goes on you seem to have a number of other things connected. A schematic or block diagram would be extremely helpful.

alexandros301: After that I get some strange behaviour

Without a schematic or block diagram, it's going to be difficult to diagnose what "modules" and "circuit" means in your context.

alexandros301: I think that 3A cannot pass through such a thin cable, right? But still, I think that 3A are a bit too much for this circuit.

Without a schematic or block diagram, it is going to be difficult to tell where 3A would be flowing.

alexandros301: I'm powering the Teensy with a different power supply with common grounds.

Again, without a schematic or block diagram it's going to be difficult to provide any decent answers.

Thanks for you replies. @James C4S I tried to upload the schematic but it didn't go through, so I've uploaded it on my website. Here's a .png of the schematic http://drymonitis.spgl.cc/modular_generic.png

It's rather messy, it's my first attempt to design a circuit board.

@DVDdoug, I've put the capacitors you mention on each chip. They're not on the schematic cause when I made it I didn't know about this, so I've soldered them on the back side of each board, in a hackish fashion. Also, I'm using a heat sink with the voltage regulator, so it should give sufficient Amps, I guess...

cheers