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	<title>Comments for Projects &amp; Libraries</title>
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	<lastBuildDate>Sat, 14 Nov 2009 17:55:50 +0000</lastBuildDate>
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		<title>Comment on Eureka! The Dot Matrix Displays Work! by David Cary</title>
		<link>http://cuznersoft.com/wordpress/?p=47&#038;cpage=1#comment-866</link>
		<dc:creator>David Cary</dc:creator>
		<pubDate>Sat, 14 Nov 2009 17:55:50 +0000</pubDate>
		<guid isPermaLink="false">http://cuznersoft.com/wordpress/?p=47#comment-866</guid>
		<description>I have learned to start a little file with every project: &quot;Things that I would do differently if I ever do this project again&quot;.
Little tweaks that are not really worth fabbing a fresh PCB -- but if I were to fab a fresh PCB anyway for other reasons, I would go ahead and make those tweaks also.

I&#039;ve seen lots of people end up with transistors in hand that had a slightly different pinout than what the guy who designed the board thought it would be.
They usually get 2 legs soldered down, then run a very short wire-wrap wire from the last leg to the other pad.
Or were you lucky enough to get pFETs that dropped right in?</description>
		<content:encoded><![CDATA[<p>I have learned to start a little file with every project: &#8220;Things that I would do differently if I ever do this project again&#8221;.<br />
Little tweaks that are not really worth fabbing a fresh PCB &#8212; but if I were to fab a fresh PCB anyway for other reasons, I would go ahead and make those tweaks also.</p>
<p>I&#8217;ve seen lots of people end up with transistors in hand that had a slightly different pinout than what the guy who designed the board thought it would be.<br />
They usually get 2 legs soldered down, then run a very short wire-wrap wire from the last leg to the other pad.<br />
Or were you lucky enough to get pFETs that dropped right in?</p>
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		<title>Comment on Dot Matrix Clock: Display board assembly by David Cary</title>
		<link>http://cuznersoft.com/wordpress/?p=97&#038;cpage=1#comment-865</link>
		<dc:creator>David Cary</dc:creator>
		<pubDate>Sat, 14 Nov 2009 17:55:14 +0000</pubDate>
		<guid isPermaLink="false">http://cuznersoft.com/wordpress/?p=97#comment-865</guid>
		<description>Congratulations!

I see that, like me, you turn on the power and program the CPU long before all the parts are soldered down. :-)</description>
		<content:encoded><![CDATA[<p>Congratulations!</p>
<p>I see that, like me, you turn on the power and program the CPU long before all the parts are soldered down. <img src='http://cuznersoft.com/wordpress/wp-includes/images/smilies/icon_smile.gif' alt=':-)' class='wp-smiley' /> </p>
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		<title>Comment on Dot Matrix Clock: Open sourcing the display schematic by Dot matrix clock on the way &#124; Diy all the Way</title>
		<link>http://cuznersoft.com/wordpress/?p=88&#038;cpage=1#comment-447</link>
		<dc:creator>Dot matrix clock on the way &#124; Diy all the Way</dc:creator>
		<pubDate>Sat, 12 Sep 2009 18:43:01 +0000</pubDate>
		<guid isPermaLink="false">http://cuznersoft.com/wordpress/?p=88#comment-447</guid>
		<description>[...] sent in his almost finished open source dot matrix clock. Sporting a hefty 40 x 16 display powered by a PIC 18F he has complete pixel by pixel control of [...]</description>
		<content:encoded><![CDATA[<p>[...] sent in his almost finished open source dot matrix clock. Sporting a hefty 40 x 16 display powered by a PIC 18F he has complete pixel by pixel control of [...]</p>
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		<title>Comment on Dot Matrix Clock: Open sourcing the display schematic by Dot matrix clock on the way - Hack a Day</title>
		<link>http://cuznersoft.com/wordpress/?p=88&#038;cpage=1#comment-446</link>
		<dc:creator>Dot matrix clock on the way - Hack a Day</dc:creator>
		<pubDate>Sat, 12 Sep 2009 17:49:40 +0000</pubDate>
		<guid isPermaLink="false">http://cuznersoft.com/wordpress/?p=88#comment-446</guid>
		<description>[...] sent in his almost finished open source dot matrix clock. Sporting a hefty 40 x 16 display powered by a PIC 18F he has complete pixel by pixel control of [...]</description>
		<content:encoded><![CDATA[<p>[...] sent in his almost finished open source dot matrix clock. Sporting a hefty 40 x 16 display powered by a PIC 18F he has complete pixel by pixel control of [...]</p>
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		<title>Comment on Eureka! The Dot Matrix Displays Work! by Kevin Cuzner</title>
		<link>http://cuznersoft.com/wordpress/?p=47&#038;cpage=1#comment-430</link>
		<dc:creator>Kevin Cuzner</dc:creator>
		<pubDate>Tue, 01 Sep 2009 03:48:34 +0000</pubDate>
		<guid isPermaLink="false">http://cuznersoft.com/wordpress/?p=47#comment-430</guid>
		<description>I realized the day after I ordered my boards that I should probably have used pFETs. I completely forgot about their lack of needing a higher voltage to turn &quot;on&quot; until I was doing some stuff in SPICE the other day, but I guess I will just deal with that problem once the boards get here. Your (a) option is easiest from a post-fabrication standpoint since I can just drop parts in hopefully.

As for rows not turning on I have realized that the problem is that I need a smaller resistor since current controlled devices vary the voltage to get the specified current. I still am not sure if running this short circuit will have an adverse effect, however, so it is still an option.

The actual power supply hasn&#039;t been designed yet, so at the moment my bench supply will have to suffice until my power draw gets over 800mA.</description>
		<content:encoded><![CDATA[<p>I realized the day after I ordered my boards that I should probably have used pFETs. I completely forgot about their lack of needing a higher voltage to turn &#8220;on&#8221; until I was doing some stuff in SPICE the other day, but I guess I will just deal with that problem once the boards get here. Your (a) option is easiest from a post-fabrication standpoint since I can just drop parts in hopefully.</p>
<p>As for rows not turning on I have realized that the problem is that I need a smaller resistor since current controlled devices vary the voltage to get the specified current. I still am not sure if running this short circuit will have an adverse effect, however, so it is still an option.</p>
<p>The actual power supply hasn&#8217;t been designed yet, so at the moment my bench supply will have to suffice until my power draw gets over 800mA.</p>
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		<title>Comment on Dot Matrix Clock: Down to two candidates by DavidCary</title>
		<link>http://cuznersoft.com/wordpress/?p=82&#038;cpage=1#comment-426</link>
		<dc:creator>DavidCary</dc:creator>
		<pubDate>Sat, 29 Aug 2009 19:35:42 +0000</pubDate>
		<guid isPermaLink="false">http://cuznersoft.com/wordpress/?p=82#comment-426</guid>
		<description>Often I lay out a PCB in such a way that the &quot;same&quot; component in several different packages will fit.
I&#039;ve seen many PCBs designed by other people that have similar &quot;overlapping&quot; footprints.

Would it be too much work to both put a surface-mount footprint for the small crystal on your PCB, and also extend the traces to the large crystal?

Then when you get the PCB, you can start putting on the small crystal first, and then either
(a) scream in frustration and throw the impossible-to-solder SMT part across the room, then smile as you fit in the through-hole part, or
(b) smile as the SMT part solders right into place, and you&#039;re left wondering why people make such a big deal out of SMT. Then (optional) saw through the unnecessarily-long traces that lead to the now-unused through-hole footprint.

Either way you are left smiling.</description>
		<content:encoded><![CDATA[<p>Often I lay out a PCB in such a way that the &#8220;same&#8221; component in several different packages will fit.<br />
I&#8217;ve seen many PCBs designed by other people that have similar &#8220;overlapping&#8221; footprints.</p>
<p>Would it be too much work to both put a surface-mount footprint for the small crystal on your PCB, and also extend the traces to the large crystal?</p>
<p>Then when you get the PCB, you can start putting on the small crystal first, and then either<br />
(a) scream in frustration and throw the impossible-to-solder SMT part across the room, then smile as you fit in the through-hole part, or<br />
(b) smile as the SMT part solders right into place, and you&#8217;re left wondering why people make such a big deal out of SMT. Then (optional) saw through the unnecessarily-long traces that lead to the now-unused through-hole footprint.</p>
<p>Either way you are left smiling.</p>
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		<title>Comment on Eureka! The Dot Matrix Displays Work! by DavidCary</title>
		<link>http://cuznersoft.com/wordpress/?p=47&#038;cpage=1#comment-425</link>
		<dc:creator>DavidCary</dc:creator>
		<pubDate>Sat, 29 Aug 2009 19:10:24 +0000</pubDate>
		<guid isPermaLink="false">http://cuznersoft.com/wordpress/?p=47#comment-425</guid>
		<description>Wow, that does sound odd.
Problems caused by a chip acting differently than what I think the datasheet says are annoying.

I am almost certain that driving the gate to a mere 0.26 V above +5.0 V is not turning your high-side nFETs completely on.
Most (all?) nFETs need Vgs_on over 3 V to completely turn on.
The other end of the nFET (the end we are *trying* to pull up to turn on the LEDs) is pulled up to, at most, the Vgs_threshold voltage below the gate voltage.
(oversimplifying:) If your Vgs_threshold is 3 V, and your gate voltage is 5.26 V, then the output is a mere 2.26 V above ground -- perhaps that&#039;s why shorting out the column driver resistor seemed to help.

I don&#039;t like running digital logic chips off nonstandard power voltage.
But if we give the row driver digital logic its standard power voltage, how do we turn the MOSFETs completely on?

There are at least 2 ways:
(a) Replace all the hi-side nFET with hi-side pFET. Turning on high-side pFETs by pulling the gate a few volts *down* from +5V, is much simpler than turning on nFETs by pushing the gate a few volts *up* above +5V.
Or,
(b) Use some sort of &quot;level translator&quot; &quot;high-side driver&quot; between the row driver digital logic and the high-side nFETs.
The level translator converts the 0 V to 5 V output of the row driver
to the ~1 V or less to turn the nFET hard off, and a &quot;Vpp&quot; high voltage of &quot;5V + Vgs_on&quot; or more (8 V or more?) to turn that nFET fully on.

The simplest level translator is a one-transistor NOT gate (with a cheap nFET or npn), with its pull-up resistor to the &quot;Vpp&quot; high voltage.

I hope you can easily get the Vpp you need (8 V? 10 V?) from your power supply.
There are many other clever ways to generate (&quot;bootstrap&quot;) that &quot;Vpp&quot; voltage.</description>
		<content:encoded><![CDATA[<p>Wow, that does sound odd.<br />
Problems caused by a chip acting differently than what I think the datasheet says are annoying.</p>
<p>I am almost certain that driving the gate to a mere 0.26 V above +5.0 V is not turning your high-side nFETs completely on.<br />
Most (all?) nFETs need Vgs_on over 3 V to completely turn on.<br />
The other end of the nFET (the end we are *trying* to pull up to turn on the LEDs) is pulled up to, at most, the Vgs_threshold voltage below the gate voltage.<br />
(oversimplifying:) If your Vgs_threshold is 3 V, and your gate voltage is 5.26 V, then the output is a mere 2.26 V above ground &#8212; perhaps that&#8217;s why shorting out the column driver resistor seemed to help.</p>
<p>I don&#8217;t like running digital logic chips off nonstandard power voltage.<br />
But if we give the row driver digital logic its standard power voltage, how do we turn the MOSFETs completely on?</p>
<p>There are at least 2 ways:<br />
(a) Replace all the hi-side nFET with hi-side pFET. Turning on high-side pFETs by pulling the gate a few volts *down* from +5V, is much simpler than turning on nFETs by pushing the gate a few volts *up* above +5V.<br />
Or,<br />
(b) Use some sort of &#8220;level translator&#8221; &#8220;high-side driver&#8221; between the row driver digital logic and the high-side nFETs.<br />
The level translator converts the 0 V to 5 V output of the row driver<br />
to the ~1 V or less to turn the nFET hard off, and a &#8220;Vpp&#8221; high voltage of &#8220;5V + Vgs_on&#8221; or more (8 V or more?) to turn that nFET fully on.</p>
<p>The simplest level translator is a one-transistor NOT gate (with a cheap nFET or npn), with its pull-up resistor to the &#8220;Vpp&#8221; high voltage.</p>
<p>I hope you can easily get the Vpp you need (8 V? 10 V?) from your power supply.<br />
There are many other clever ways to generate (&#8220;bootstrap&#8221;) that &#8220;Vpp&#8221; voltage.</p>
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		<title>Comment on Weekend Project: Smoke Bombs by Mark</title>
		<link>http://cuznersoft.com/wordpress/?p=62&#038;cpage=1#comment-423</link>
		<dc:creator>Mark</dc:creator>
		<pubDate>Fri, 28 Aug 2009 15:46:27 +0000</pubDate>
		<guid isPermaLink="false">http://cuznersoft.com/wordpress/?p=62#comment-423</guid>
		<description>Copious quantities of smoke... :D Gets funnier every time I hear it.</description>
		<content:encoded><![CDATA[<p>Copious quantities of smoke&#8230; <img src='http://cuznersoft.com/wordpress/wp-includes/images/smilies/icon_biggrin.gif' alt=':D' class='wp-smiley' />  Gets funnier every time I hear it.</p>
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		<title>Comment on Weekend Project: Smoke Bombs by Gabriel</title>
		<link>http://cuznersoft.com/wordpress/?p=62&#038;cpage=1#comment-324</link>
		<dc:creator>Gabriel</dc:creator>
		<pubDate>Tue, 07 Jul 2009 00:06:33 +0000</pubDate>
		<guid isPermaLink="false">http://cuznersoft.com/wordpress/?p=62#comment-324</guid>
		<description>Good Job on the smokebomb</description>
		<content:encoded><![CDATA[<p>Good Job on the smokebomb</p>
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		<title>Comment on Not so temporary&#8230; by Robert</title>
		<link>http://cuznersoft.com/wordpress/?p=3&#038;cpage=1#comment-10</link>
		<dc:creator>Robert</dc:creator>
		<pubDate>Sun, 15 Feb 2009 22:13:08 +0000</pubDate>
		<guid isPermaLink="false">http://cuznersoft.com/wordpress/?p=3#comment-10</guid>
		<description>I hope you can get the website back up to shape again!</description>
		<content:encoded><![CDATA[<p>I hope you can get the website back up to shape again!</p>
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