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Topic: 8x8x8 multiplexed LED cube with an Arduino Mega 2560 (Read 41 times) previous topic - next topic

Un4Seen

Rds(on) = 0.05 Ohms then, so it's good :)

Thanks!

Un4Seen

#91
Dec 31, 2012, 12:38 am Last Edit: Dec 31, 2012, 12:50 am by Un4Seen Reason: 1
For anyone else who might be interested in the future to build a LED cube based on this design, I've put together a component list with prices based on what I have bought for the project. I tried to buy the components as cheap as I could, most of them off eBay, but for many of them I have bought more than actually necessary, because they sell in bulk or because I wanted some spare parts. Here's what I got:

NDP6020P: 14 pcs 33.3 EUR (43.8 USD)
3mm diffused blue LEDs: 1000 pcs 19.4 EUR (25.5 USD)
TPIC6B595N shift registers: 20 pcs 9.3 EUR (12.3 USD)
1K variable resistors: 100 pcs 7.4 EUR (9.8 USD)
5V 3A power supply: 1 pcs 7.1 EUR (9.4 USD)
Craft wire 0.8mm 6m: 3 pcs 7 EUR (9.2 USD)
Jumper cables 40 PCS: 2 pcs 6 EUR (7.9 USD)
Capacitors (0.1 uF) + resistors (82R, 220R): 3 pcs 4.6 EUR (6.1 USD)
PCB 18x12 cm: 2   pcs 3.9 EUR (5.2 USD)
Female pin headers: 200 pcs 3.8 EUR (4.9 USD)
TO-220 heatsink: 10 pcs 3.4  EUR (4.5 USD)
IC sockets DIP-20 for TPIC6B595N: 10 pcs 2 EUR (2.7 USD)
Crocodile clips: 2 pcs 0.8 EUR (1 USD)
Total: 108 EUR (142.3 USD)

Sorry, I just can't get the data into a well-formatted table.

This does not include, of course, the price of the Arduino driving the cube or other miscellaneous stuff like soldering materials or the prices of some tools that you use for other projects too.

Hippynerd

Somehow I got lost on the math there DC. 1.28 * 1.28 = 1.6384, divide by 4 and you get .4096.
How do you come up with .5 watt?
He will need 8 mosfets, each one will run 1/8th of the time (12.5%), each one will need to be able to source between 0 and 1.28A. I see the 1.28 in there, and the 4 was from half watt times 8. So I see some of the numbers, and understand where they came from, Im still confused with the math, and where half a watt came from. it seems arbitrary. 

I tried crossroads technique, and came up with 7 P-channels, I started by searching "p-channel mosfet", then clicked a link that said Fets-Single, That displayed a page with many options, I selected logic level gate, through-hole, and then I scrolled the package column, and selected the TO-220-3

From there, I notice that all of the parts have many mOhm RDS (way way over .4 ohm), not even close to mOhms.
I dont know what a good/bad gate capacitance is, but I can only find gate charge, and input capacitance.

I can also see that the NDP6020 is rated at 60 watts, and if using 1/2 watt, Im guessing you wouldnt need a heatsink.
How many 20mA LEDs could you run on that mosfet?

Also $150 for the parts for a 8x8x8 cube sounds like a lot, but I havnt built a cube that big.

6 Meters of wire seems like a low estimate to me too, I bet you use over 8. what kind of wire is it? soft wire is very difficult, but harder wire is a bit easier, and ends ups being sturdier. I find very hard steel works the best. For cube building, and general keeping wires straight, thinner and softer are more difficult, thicker and harder are easier, but for soldering, thinner is easier.

Un4Seen

Hi!

I'm planning to run 64 20 mA LEDs from one of those MOSFETS.
That price of 142$ includes components for the big 8x8x8 cube, but also for the small 4x4x4 learning cube and some spares. I guess that if I tried to but onyl as many components as necessary for the 8x8x8 cube only, I could have pulled it off for about 100$.

6m of craft wire is definitely not enough. But I have bought 3x6=18m, which is probably twice as much as I need. I do not know how soft or hard it is, I bought it blindly from eBay based on the suggestion of somebody who has already used the same or similar craft wire to build a LED cube successfully. It is 0.8mm thick and is sold rolled up, I'll have to straighten it before soldering.

dc42


Somehow I got lost on the math there DC. 1.28 * 1.28 = 1.6384, divide by 4 and you get .4096.
How do you come up with .5 watt?


See reply #83. I suggested a maximum of 1W for a TO220 mosfet with no heatsink, and 0.5W for a mosfet in a smaller package.
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