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Anyone wanting to control many LEDs should perhaps check out the TLC5947 - it can control 24 LEDs using PWM (or 8 x 3 LEDs for R G B). Check datasheets for more info.<BR>
<BR>
<A HREF="http://hackedgadgets.com/2010/11/10/rgb-led-circuit-using-the-tlc5947">http://hackedgadgets.com/2010/11/10/rgb-led-circuit-using-the-tlc5947</A><BR>
<BR>
Cheers<BR>
<BR>
On Tue, 2010-11-16 at 07:26 +1300, Nathan Kennedy wrote:
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<PRE>
I did a bulk order of 74HC595 a while back when I was building my xmas light
controllers (unfortunately we're not doing our display this year due to
quake damage), and I've got a few left over.
I can do them at $1 each (inc gst) if you (or anyone) is interested.
Thanks,
Nathan.
-----Original Message-----
From: <A HREF="mailto:chchrobotics-bounces@lists.linuxnut.co.nz">chchrobotics-bounces@lists.linuxnut.co.nz</A>
[<A HREF="mailto:chchrobotics-bounces@lists.linuxnut.co.nz">mailto:chchrobotics-bounces@lists.linuxnut.co.nz</A>] On Behalf Of Mark
Atherton
Sent: Tuesday, 16 November 2010 7:01 a.m.
To: <A HREF="mailto:chchrobotics@lists.linuxnut.co.nz">chchrobotics@lists.linuxnut.co.nz</A>
Subject: [chbot] PWM control of William's LED display
William,
I have some thoughts about how you could control the brightness of
your LED display unit using PWM.
Brielfy, an 8 bit shift register (74x595 etc) is loaded with a
brightness value (0..255) this is fed into the A side of an 8 bit
magnitude comparator (2 x cascaded 74x85 etc.). The B side of the
comparator is fed with a continuously running 8 bit binary counter.
This counter needs to wrap around at about 100Hz. The ">" output of
the cascaded 74x85 then becomes the PWM brightness control signal and
feeds the enable signal of each of the LED drivers.
South Island Components's (how do you pluralize that ?) web site
claims to have everything in stock...
datasheets:
<A HREF="http://www.nxp.com/documents/data_sheet/74HC_HCT85_CNV.pdf">http://www.nxp.com/documents/data_sheet/74HC_HCT85_CNV.pdf</A> and
<A HREF="http://www.fairchildsemi.com/ds/MM/MM74HC595.pdf">http://www.fairchildsemi.com/ds/MM/MM74HC595.pdf</A>
Anyway, just a thought after too much coffee.
-Mark
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