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Topic: Led Cube 8x8x8 (Read 1 time) previous topic - next topic

Yogpeople

I need help i am in grade 10 and i am trying to make a led cube 8x8x8 i am using shift registers and using arduino but i dont know how to wire it or power it plz help me thank you

here is the link to the picture
http://imgur.com/oYlmM

CrossRoads

How is it wired up so far? Anodes connected in columns, cathodes connected in layers?
So 64 anodes would be driven high by 8 shift registers (thru current limit resistors) and you'll add a 9th shift register to control 8 N-channel MOSFETs to sink the current (up to 64 * 20mA = 1.28A) from 1 layer at a time?
Shift registers controlled by SPI.transfer() commands for nice fast updating?
5V, 2A power supply  like this would be sufficient.
http://www.dipmicro.com/store/DCA-0520
Use 1 resistor per anode column, value of (5V - (Vf of LED, ~1.7V for Red?) )/20mA = 165 ohm , 180 is standard value and would work well.
Use Low Rds, Logic Level N-channel MOSFETs such as
http://www.digikey.com/product-detail/en/NTD5867NL-1G/NTD5867NL-1GOS-ND/2401422

turn all cathode off, drive the anodes, turn 1 cathode on, in 5mS turn it off, drive anodes for next layer, turn next cathode on, in 5mS turn it off, repeat for next 6 layers.
During the 5mS, your code can be doing something else.

Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Yogpeople

Sorry for the late reply. we are useing 74hc595n shift registers, the positive leads are connected in columns down the cube and the negatives are connected in layers. We are trying to use a 64-bit binary pulse from an arduino uno to turn on the leds. We also have access to the arduino leonardo and arduino due. Can you please also clarify on the 8 N-channel MOSFET.

CrossRoads

So you've got something like this then, but expanded across the page to be 64 LEDs/layer.
You would drive the anodes from 8 shift registers, then drive the cathode for 1 layer low.
Repeat for the next 7 layers.
With the LEDs on full, you could have 20mA * 64 LEDs = 1.28A if all LEDs are on.
A  N-channel MOSFET with low Rds (like 30mOhm) will not heat up if turned on/off quickly, dissipating just 1.28A*1.28A*.03ohm =  50mW, while an NPN transistor will dissipate ~0.7V * 1.28A = 900mW everytime it turns on.

This would be a good Logic Level, Low Rds, Low Gate capacitance, high current, low cost, N-channel MOSFET.
http://www.digikey.com/product-detail/en/NTD5867NL-1G/NTD5867NL-1GOS-ND/2401422
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

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