How to power my circuit.

On Mon, 13 Aug 2012 03:34:40 -0700 (PDT), fungus
<tooby@artlum.com> wrote:

>On Monday, August 13, 2012 10:22:41 AM UTC+2, Jon Kirwan wrote:
>>=20
>> I'd have to check my notes. But I remember that they roughly
>> dissipate about 80W per.
>>=20
>
>So a dozen panels is a kilowatt. A big
>display is more like 20kW... 180Amps?*
>Get a big thick cable.
>
>*(at 110VAC)

Well, if you look at Ebay you will see 8x8 RGB without driver
chips. Each LED accepts 20mA, but at 3V, 3V, and 2V. So you
are talking about 160mW per, if on full. That doesn't count
any losses anywhere else supplying that. With 64, that's
about 10W. My panels are 4X as much. So that would be 40W
already. And you still don't have the drivers and their
losses. And besides, these LED panels I have are very high
efficiency and designed for outdoors so quite bright.
Regardless, you can see that the 80W figure is probably in
the ballpark. So my memory may have been correct. I think the
peak current was around 25mA for each LED.

Each IC was a 76 pad, 16x8 pixel controller with on-chip
static ram, EEPROM, Address Decoders, Multiplex circuitry and
constant current driver. It used 0.5um double metal, double
poly, CMOS technology.

Some features of these ICs were:

	8 rows x 16 columns driver matrix.
	Inter-digit blanking of 1/32 times the row-on period.=20
	Programmable column driver constant current sources.
	Up to 31 Levels of PWM global brightness control.
	7 Bit global peak current digital brightness trim
		in non-volatile memory.
	7 Bit peak current global color correction from a
		second color in non-volatile memory.
	1024 values of programmable pre-scale for the
		multiplex clock.
	Internally buffered signal feed-through for serial
		cascading of devices
	24 Bit pulse counter (run time) in NV memory with
		selectable 50 or 60Hz signal input.
	70 MHz maximum serial shift clock and multiplex
		clock frequency
	30ms Deadman timer feature to prevent extended
		direct current drive
	130C Over-temp protection.
	Half-multiplex (1/8 to 1/4) feature to decrease
		peak current.
	Programmable stagger of column drivers for reduced EMI

Pretty fancy, all in all.

All this was built into a module with a metal, drilled out
face for each RGB LED and a heavy heat sink on the backside.
You supplied power and serial communications.

It would take some serious design, microcontrollers, and four
of those RGB 8x8 on Ebay (they seem to got for about $7-8
each) to put the equivalent together. They sold, in qty, for
about $70 each. And that was some years ago. They are OSRAM
devices.

And yes, a 200x300 matrix (VHS supported 210 lines) would be
about 250 devices or something like that. I think the
displays rarely had all the pixels full-on all the time, so I
think 10kW was the area folks considered for design. It was
still a LOT of power. So heat (and the communication rate and
distribution to keep 30 frames per second going) were the
main issues, I think.

Jon

Here's a picture of the devices:

http://www.infinitefactors.org/misc/images/p1000046_640x480.jpg

3mm diameter pixel on a 4mm pitch, with a wide viewing angle.

Jon

Daniel Pitts schrieb:

> So to power 192 LEDs (8x8xRGB) I could spend spend over $30 using 
> MAX7219, or I could spend just 3*.88+.25=$2.89. I think a 90% cheaper 
> solution is the better solution, especially for a hobby project.

Hello.

if you want to power 192 LEDs with a mean current of 10 mA, you will 
need 1.92 A only for the LEDs if all are on. That is too much for three 
AA cells in series. Use a wall wart as recommended by the other posters.

Bye

On Monday, August 13, 2012 5:43:52 PM UTC+2, Uwe Hercksen wrote:
> 
> if you want to power 192 LEDs with a mean current of 10 mA, you will 
> need 1.92 A only for the LEDs if all are on. That is too much for three 
> AA cells in series. Use a wall wart as recommended by the other posters.
> 

They will never all be on at the same time,
only a single column of 8 LEDs. The maximum
power is only 80mA.

On 8/12/12 3:52 AM, fungus wrote:
> On Saturday, August 11, 2012 1:05:57 AM UTC+2, fungus wrote:
>>
>> thinking it might be a good time to get
>> started on my own LED cube. :-)
>
> I gave in to temptation, ten MAX7219s for $5.10
>
> http://www.ebay.com/itm/300739928460
>
> Now I just need a load of LEDs and my
> cube will be under way...
>
> I think I'll go for 5x5x5 - 7x7x7 is
> three times as many LEDs, that's a lot
> more work/expense than 5x5x5.
>
If you want to get cheap LEDs, search for a batch of 1000 on ebay. I've 
gotten them around 1� an LED for reds/yellows/greens. and 2� to 3� for 
teal/uv  (I was trying to get blue, but teal was what I got. My bad for 
not looking at the wavelength)

Note, 1000 is not quite enough for a 32x32 display. It is plenty for a 
single 8x8x8 cube, with enough left over to also make a 7x7x7. You can 
make 8 5x5x5 with 1000 leds.

On Tuesday, August 14, 2012 8:30:43 PM UTC+2, Daniel Pitts wrote:
>=20
>=20
> > I think I'll go for 5x5x5 - 7x7x7 is
>=20
> > three times as many LEDs, that's a lot
>=20
> > more work/expense than 5x5x5.
>=20
> >
>=20
> If you want to get cheap LEDs, search for a batch of 1000 on ebay. I've=
=20
>=20
> gotten them around 1=EF=BF=BD an LED for reds/yellows/greens. and 2=EF=BF=
=BD to 3=EF=BF=BD for=20
>=20
> teal/uv  (I was trying to get blue, but teal was what I got. My bad for=
=20
>=20
> not looking at the wavelength)
>=20

Yep, I did that. There's 500 3mm diffuse blue
LEDs on the way.

I still didn't decide between 5x5x5 and 7x7x7.
It's a lot more LEDs but the wiring/programming
isn't really more difficult. Might have to forget
about USB power, too.

OTOH my girlfriend likes soldering...every time
I get the soldering iron out she's like, "Oh,
let me do it..."

On 8/15/12 4:31 AM, fungus wrote:
> On Tuesday, August 14, 2012 8:30:43 PM UTC+2, Daniel Pitts wrote:
>>
>>
>>> I think I'll go for 5x5x5 - 7x7x7 is
>>
>>> three times as many LEDs, that's a lot
>>
>>> more work/expense than 5x5x5.
>>
>>>
>>
>> If you want to get cheap LEDs, search for a batch of 1000 on ebay. I've
>>
>> gotten them around 1� an LED for reds/yellows/greens. and 2� to 3� for
>>
>> teal/uv  (I was trying to get blue, but teal was what I got. My bad for
>>
>> not looking at the wavelength)
>>
>
> Yep, I did that. There's 500 3mm diffuse blue
> LEDs on the way.
>
> I still didn't decide between 5x5x5 and 7x7x7.
> It's a lot more LEDs but the wiring/programming
> isn't really more difficult. Might have to forget
> about USB power, too.
Well, if you have good multiplexing and don't need to run at a high 
duty-cycle, USB might provide enough power.
>
> OTOH my girlfriend likes soldering...every time
> I get the soldering iron out she's like, "Oh,
> let me do it..."
Lucky you.  I wasn't able to even start on electronics projects until I 
was single. ;-)

Although, it was for other reasons.

On 8/7/12 5:39 PM, Daniel Pitts wrote:
> Hello,
>
> So far, all of my circuits have had the power supplied by an Arduino
> (compatible) board.  I'm going to try to change the setup here a little,
> and design a circuit that has just an ATTiny in its place, but now I
> have to think about power supply.
>
> The circuit I'm envisioning is going to have three Texas Instruments
> "TLC5916" constant-current sink's, powering one column of a multiplexed
> 8x8 RGB led matrix. The circuit will also have an ATTiny85 (or ATTiny84,
> depending on a few things), and a 74HC238 (to select the row on the LED
> matrix).
>
> Now, if I'm reading the specs right, I think I can power the whole thing
> on 3 AA batteries (4.5 volts). But if I wanted to have more robust power
> handling, I'm not sure what I want to do.  I'd like to try to keep the
> circuit cheap, and potentially have it powered by a wall socket or USB.
> I also don't have the time/money to etch my own PCB, so something that I
> can plug into my protoboard is preferable.
>
> Is it just me, or is deciding on a power supply a relatively difficult
> problem, compared to other aspects of working on digital circuitry?
>
> Thanks in advance for any suggestions!
>
> --
> Daniel.


Thanks to everyone who gave advice.

For prototyping purposes, I ended up buying a 5v linear voltage 
regulator from Radio Shack.  It lets me power my project from a 9v 
battery.  I don't know how the performance is, whether it's sufficient 
for a wearable or always-on.  If I wanted a non-wearable always-on, I 
can get a wall adapter.

On Thursday, August 16, 2012 5:42:17 PM UTC+2, Daniel Pitts wrote:
> 
> > I still didn't decide between 5x5x5 and 7x7x7.
> > It's a lot more LEDs but the wiring/programming
> > isn't really more difficult. Might have to forget
> > about USB power...
> 
> Well, if you have good multiplexing and don't need to run at a high 
> 
> duty-cycle, USB might provide enough power.
> 

With one MAX7219 chip per layer I could have
49 LEDs on at the same time. They can control
the brightness with PWM so I guess I could
have a switch on the box for "USB mode" to
lower the power a bit. Maybe I can also have
an indoor/outdoor setting as well - run the
LEDs at higher power.

I should probably build in some sort of
safety features if I do that though. USB
doesn't have over-current protection AFAIK.

First I have to see how bright the LEDs are
in real life.

On 2012-08-16, Daniel Pitts <newsgroup.nospam@virtualinfinity.net> wrote:
>> So far, all of my circuits have had the power supplied by an Arduino
>> (compatible) board.  I'm going to try to change the setup here a little,
>> and design a circuit that has just an ATTiny in its place, but now I
>> have to think about power supply.
>>
>> The circuit I'm envisioning is going to have three Texas Instruments
>> "TLC5916" constant-current sink's, powering one column of a multiplexed
>> 8x8 RGB led matrix. The circuit will also have an ATTiny85 (or ATTiny84,
>> depending on a few things), and a 74HC238 (to select the row on the LED
>> matrix).
>>
>> Now, if I'm reading the specs right, I think I can power the whole thing
>> on 3 AA batteries (4.5 volts). But if I wanted to have more robust power
>> handling, I'm not sure what I want to do.  I'd like to try to keep the
>> circuit cheap, and potentially have it powered by a wall socket or USB.
>> I also don't have the time/money to etch my own PCB, so something that I
>> can plug into my protoboard is preferable.
>>
>> Is it just me, or is deciding on a power supply a relatively difficult
>> problem, compared to other aspects of working on digital circuitry?
>>
>> Thanks in advance for any suggestions!
>>
>> --
>> Daniel.
>
>
> Thanks to everyone who gave advice.
>
> For prototyping purposes, I ended up buying a 5v linear voltage 
> regulator from Radio Shack.  It lets me power my project from a 9v 
> battery.  I don't know how the performance is, whether it's sufficient 
> for a wearable or always-on.  If I wanted a non-wearable always-on, I 
> can get a wall adapter.

Those 9V batteires are one of the most expensive ways to buy electricity,
and the regulator is throwing almost half the energy away.

4 rechargable AA Nimh cells get you the voltage you need and will run
for 5 times longer between charges. 4xAAA cells will cost about the
same as AA but be about as heavy as the 9V and still outlast it by a
factor of 2 

-- 
&#9858;&#9859; 100% natural

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