6x6x6 LED cube with Attiny85 - Page 1
Forum section: electronics / projects

author: 00
author_rank: Contributor
timestamp: February 04, 2021, 08:24:28 pm
content: Hi everyone!I want to make a 6x6x6 LED cube that is controlled by one Attiny85 instead of Arduino etc. I have been thinking about it and made a schematic(see in the attachment).Five SN74HC595N are going to control the cathodes("+" terminals) for the 36 columns of the cube. The 6th shift register is going to turn on/off the layers of the cube(control anodes).All 5 shift register outputs each are connected to 220R resitors(each one for each column). The outputs of 6th shift register are connected to S8050 NPN BJTs(each capable of continuous >700mA).1. At the first glance, is it going to work? Are there any delays in microcontrollers that could cause problems?2. Are all components capable of driving these LEDs? Only one layer will be turned on at time, so I think that everything shoul be OK.3. Maybe this circuit isn't so effective, for example, only one layer turned on.4. Are there any other potential problems?I know that it may not be smart to do this, but I want to make it.

author: mino-fm
author_rank: Regular Contributor
timestamp: February 04, 2021, 09:58:02 pm
content: Another way to go would be using C4094 shift-registers. Each output is capable to drive around 5 mA @ 5 V without an extra current limiting resistor. Its output resistance is sufficient. Lower VCC will reduce output current.You would need 5 pieces of C4094 to drive one plane (max. 40 leds) and all together 30 x C4094 for the cube.Let me show you an example of driving 6 x 7-segment digits:http://www.mino-elektronik.de/7-Segment-Variationen/LCD.htm#led1

author: 00
author_rank: Contributor
timestamp: February 05, 2021, 07:33:22 am
content: Yes, I could also choose other options, but I already have like 20 shift regsters and plenty of resistors, that's why I chose these.Are there any visible flaws in my circuit or now I only need to asseble everything and see what happens?

author: larsdenmark
author_rank: Regular Contributor
timestamp: February 05, 2021, 08:32:59 am
content: I don't think it will work.You want to use the output of QH' (and not QH) as input to the next shift register. That way you can send the data for all the shift registers and then to an update of all the outputs in one go.It is probably not necessary, but it doesn't hurt to have a decoupling capacitor for each IC.It is probably just a mix of words, but you write:cathodes("+" terminals)but "+" are anodes! In your design your want the transistors to be close to ground "-" and the 5 shift registers to be positive "+". You don't want to mix this up when soldering 216 LEDs.

author: 00
author_rank: Contributor
timestamp: February 05, 2021, 10:37:44 am
content: Thanks! I didn't check twice. Yes, I meant anodes("+" terminals) and cathodes("-" terminals).I don't really understand why should I use output QH'. Isn't it opposite of QH? If it is opposite, wouldn't it inverse all data sent from 1st shift register etc.? If I want QA pin for 2nd register high, wouldn't it be low because it takes opposite of what I send as input?About decoupling capacitors. I didn't include them because in my opinion they are necessary, but take up a lot of space in schematic.

author: larsdenmark
author_rank: Regular Contributor
timestamp: February 05, 2021, 12:28:42 pm
content: Every time you flip the latch clock signal the data stored in the shift register are sent to the outputs. This is true for QA to QH (for all shift registers).Meanwhile, The QH' is immediately shifted from one register to the next, which means that you can load all the data into the shift registers and then when you flip the latch clock signal all shift registers will use the data as outputs at the same time. This reduces flicker.Here is a random link to a diagram where it is done:https://www.electroschematics.com/multiple-shift-registers-arduino-part-1/I would definitely use a decoupling capacitor for the MCU.

author: 00
author_rank: Contributor
timestamp: February 05, 2021, 06:30:13 pm
content: Thanks! Very helpful!