On 8/17/12 4:20 PM, Jasen Betts wrote:
> On 2012-08-16, Daniel Pitts <newsgroup.nospam@virtualinfinity.net> wrote:
>> 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
>
Thanks for the tip.

The regulator I bought (from radio shack, just to get started on 
something) has a rated minimum voltage of 7v, which is just above 4xAA. 
  However, I don't know that my project needs a full 5v. I actually have 
a 4xAA pack, so I could try it and see if it powers my project sufficiently.

If I ever "mass produce" this project (meaning make more than 1), I'll 
try to find a more efficient power system.

Thanks,
Daniel.

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

--- Posted via news://freenews.netfront.net/ - Complaints to news@netfront.net ---

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 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 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&#65533; an LED for reds/yellows/greens. and 2&#65533; to 3&#65533; 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 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 8/12/12 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&#4294967295; an LED for reds/yellows/greens. and 2&#4294967295; to 3&#4294967295; 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 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.


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