8x8x8 multiplexed LED cube with an Arduino Mega 2560

CrossRoads:
Wow, 10 pieces for $7.50 - that adds a lot to cost of the MOSFET!

Unfortunately, yes - although SMD mosfets are so cheap that it still costs less than using a TO220 mosfet (but a lot more work of course).

One day I'll get round to sending an SMD adapter design off to Itead to reduce the cost. It would be useful to have boards that take 2 or 4 SOT23 devices too.

Un4Seen:
I live in Romania, so have 3 options:

Have you tried http://ro.farnell.com/?

Is Farnell expensive in Romania?
For a part like this?
I don't know what this price relates to in US dollars.

I bought a sheet of adapters like
http://www.ebay.com/itm/SMD-CONVERTER-ADAPTER-PCB-SOT-TO-MSOP-SIP-DIP-14-/270832318388?pt=LH_DefaultDomain_0&hash=item3f0edd37b4
Probably had like 20 each of the different adapters on it.

I have just tried Farnell. They sell it for about 2.5$, same as the Chinese eBay seller (which could be fake). They say it's coming from UK, so it would probably take less time. The problem is however, that they haven't got a user-friendly site and I just can't figure out how much the transport to Romania would be without trying to actually buy the stuff :slight_smile:

CrossRoads:
Is Farnell expensive in Romania?
For a part like this?
I don't know what this price relates to in US dollars.
http://ro.farnell.com/international-rectifier/auirf4905/mosfet-w-diode-p-ch-55v-74a-to220ab/dp/1865604

They sell the one you originally suggested for less, see http://ro.farnell.com/fairchild-semiconductor/ndp6020p/mosfet-p-to-220/dp/1017724?Ntt=NDP6020P-ND.

PS - 7.06 RON = 2.10066 USD according to xe.com

Un4Seen:
I have just tried Farnell. They sell it for about 2.5$, same as the Chinese eBay seller (which could be fake). They say it's coming from UK, so it would probably take less time. The problem is however, that they haven't got a user-friendly site and I just can't figure out how much the transport to Romania would be without trying to actually buy the stuff :slight_smile:

If you go through the order placement process, I think you will find the carriage cost (if any) added on before you get asked for your credit card details. It may be free, some of the stuff I buy from Farnell gets shipped form mainland Europe and I don't get charged extra. You may find there is a minimum order, it's GBP20 here in the UK for non-business accounts.

OK, I have figured it out :slight_smile: As I wrote, one NDP6020P costs about 2.5$ at Farnell. The transport to Romania would be 5 Euro, regardless of what is in the package. So, assuming that I'd buy 15 pieces of NDP6020P (8 for the 8x8x8 cube, 5 for the 5x5x5 cube and 2 for spares), the total cost would be around 27E or 35$. That's more than the 1000 LEDs and about 33% of the total project cost :slight_smile: I there's no other choice, I'll go for it, but if there's some more widely available, less expensive MOSFET, I'd prefer that :slight_smile:

CrossRoads:
I bought a sheet of adapters like
http://www.ebay.com/itm/SMD-CONVERTER-ADAPTER-PCB-SOT-TO-MSOP-SIP-DIP-14-/270832318388?pt=LH_DefaultDomain_0&hash=item3f0edd37b4
Probably had like 20 each of the different adapters on it.

That looks excellent, I'll order one.

Unfortunately, P-channel MOSFETs and PNP transistors seem to be pricey compared to N-Channel & NPNs.

From my point of view the biggest problem is not that they are pricey, it's that they are rare. Otherwise I could buy them here at home or on eBay :slight_smile: I just talked to a friend and he says that Farnell only ships to Romania for companies, not for individuals. I'll have to check that out.

Okay, so can they ship to Un4Seen, Incorporated?

I just searched eBay for P-channel mosfets and got 156 results. The SMD ones are inexpensive, the TO220 ones cost a lot more and are mostly not logic level.

Might be worth trying RS as well, http://ro.rsdelivers.com/.

Un4Seen:
OK, I have figured it out :slight_smile: As I wrote, one NDP6020P costs about 2.5$ at Farnell. The transport to Romania would be 5 Euro, regardless of what is in the package. So, assuming that I'd buy 15 pieces of NDP6020P (8 for the 8x8x8 cube, 5 for the 5x5x5 cube and 2 for spares), the total cost would be around 27E or 35$. That's more than the 1000 LEDs and about 33% of the total project cost :slight_smile: I there's no other choice, I'll go for it, but if there's some more widely available, less expensive MOSFET, I'd prefer that :slight_smile:

All the suitable but less expensive p-channel mosfets I found were in SMD packages - and they are MUCH less expensive. So I think your alternative is to download Eagle and design a pcb to hold a 74HC595 and eight SMD mosfets. Then get Itead to make 10 of them for $9.90. Add mosfets such as http://www.ebay.co.uk/itm/20PCS-AO3401-SOT-23-P-Channel-MOSFET-TRANSISTORS-/150653948679?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item2313acd307.

I ordered some of these from thaishine.com
N
Manufacturer Part No: IRF3205

Specification
Mosfet Type N-channel
Current Rating 110A
Rds (On) 8m?
Voltage Rated 55V

P
Manufacturer Part No: IRF9540

Description
MOSFET
Transistor Type:MOSFET
Transistor Polarity:P Channel
Drain Source Voltage, Vds:-100V
Continuous Drain Current, Id:-23A
On Resistance, Rds(on):117mohm
Rds(on) Test Voltage, Vgs:-10V

They were under $1 each in packs of 10.

I also found these (below), after I had ordered the above fets.

Mosfet Type: P-channel
Current Rating: 2.6A
Rds (On): 40 mOhm
Voltage Rated: 12V
Package: SSOT-3

Mosfet Type: N-channel
Current Rating: 4A
Rds (On): 100 mOhm
Voltage Rated: 60V
Package: SOT-223

They are smaller package, but probably suitable for my 1 amp needs. they may be suitable for 1.3 amp, you have to check.

Im not sure which one I got it from, thaishine also sells through ebay.
www.thaishine.com
www.taydaelectronics.com

I am way behind on those cubes, and I havnt had a chance to use the parts, but I assume they will be good for cubes/multiplexing.

dc42, are those tiny sot23 parts going to be able to handle 1.28 amps? they seem pretty small for that. I looked, but I didnt see any datasheet.

Wow, 4 amps from such a tiny package. I wish I had gotten those now.

Yes, see http://www.aosmd.com/pdfs/datasheet/AO3401.pdf. They are rated at 4A continuous (although 3.7A would be a more realistic limit when driven from 5V, since that is the current at which Rds(on) is measured for Vgs=4.5V) and 1.4W power dissipation (although I wouldn't want to dissipate more than a few hundred mW in one).

Guys, did I understand correctly, that the IRF9540 would be able to do the job and I could use it instead of the NDP6020P?
I've found them on eBay and for a good price too: http://www.ebay.com/itm/10pcs-IRF9540-P-Channel-Power-MOSFET-23A-100V-TO-220-IR-Free-Shipping-/180816152092?pt=LH_DefaultDomain_0&hash=item2a197b861c

It seems to be a fast switching P-channel MOSFET in TO-220 packaging, rated at 23A and 100V. What do you think?

Thanks,
Andras

Seems to be a logic level part

Will have at least 1V drop across it, see Figure 2.

TPIC6B595 will have 3-4 ohms of resistance, see Figure 7, at 20mA = another 0.07V

So as long as your LEDs have Vf <(5-1-.07) = 3.93V you should be okay.
Adust your current limit resistors accordingly.