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<?xml-stylesheet type="text/xsl" href="https://community.arm.com/utility/feedstylesheets/rss.xsl" media="screen"?><rss version="2.0" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:slash="http://purl.org/rss/1.0/modules/slash/" xmlns:wfw="http://wellformedweb.org/CommentAPI/"><channel><title>AC square wave constant voltage</title><link>https://community.arm.com/developer/tools-software/tools/f/keil-forum/22433/ac-square-wave-constant-voltage</link><description> 
hi friends, 

 
Do you have an idea or circuit for &amp;quot;AC square wave constant
voltage generator&amp;quot; with short circuit protection ? 
The spec: 
1. The square wave output is 24v 200mA. 
2. Max load&amp;#39;s resistance is 8000 ohm 
3. When the load&amp;#39;s resistance is</description><dc:language>en-US</dc:language><generator>Telligent Community 10</generator><item><title>RE: AC square wave constant voltage</title><link>https://community.arm.com/thread/135405?ContentTypeID=1</link><pubDate>Wed, 11 Jun 2008 11:54:55 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:c9f919f5-dda6-419d-97b1-e83a26b73958</guid><dc:creator>ImPer Westermark</dc:creator><description>&lt;p&gt;&lt;p&gt;
You are an order of magnitude off. The specified load was 8 kohm,
not 800 ohm, so it would take 1,6kV to drive 200mA through the load,
and the power sent into the load would be 320W at 50% (?) duty
cycle.&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: AC square wave constant voltage</title><link>https://community.arm.com/thread/124723?ContentTypeID=1</link><pubDate>Wed, 11 Jun 2008 06:56:55 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:a3dcee80-89ba-4045-8d86-670a73607bbc</guid><dc:creator>D Tiziano</dc:creator><description>&lt;p&gt;&lt;p&gt;
Additionally&lt;/p&gt;

&lt;p&gt;
24 V on 800 ohm get 30 mA so you have to check your
specification.&lt;br /&gt;
For 800 ohm load you need at least a generator with 160 V.&lt;/p&gt;

&lt;p&gt;
For a simple on/off a switched constant current generator can do
the job (the frequency can be the problem if too high).&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: AC square wave constant voltage</title><link>https://community.arm.com/thread/114014?ContentTypeID=1</link><pubDate>Wed, 11 Jun 2008 01:27:21 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:dd53c8e4-b45d-4a4a-b0df-80df3a6b8e55</guid><dc:creator>ImPer Westermark</dc:creator><description>&lt;p&gt;&lt;p&gt;
Anyway, you don&amp;#39;t specify any load regulation for your generator.
If you really did mean that max load is 8000 ohm, then you can select
a trivial solution.&lt;/p&gt;

&lt;p&gt;
Just use a 24V linear voltage regulator and feed the 24V to a
switch transistor controlled by a logic-level squarevave
generator.&lt;/p&gt;

&lt;p&gt;
Place a 120 ohm resistor between transistor and connector.&lt;/p&gt;

&lt;p&gt;
Your short-circuit current will then be 24V/120ohm = 200mA.&lt;/p&gt;

&lt;p&gt;
Your open-circuit voltage will be 24V (minus a little loss in the
switch transistor).&lt;/p&gt;

&lt;p&gt;
Your fully loaded current will be 24V / (120 + 8000) A =
0.00296A.&lt;/p&gt;

&lt;p&gt;
Your fully loaded volage will be 24V - 24 * 120 / (120 + 8000) V =
23.65V (minus a little loss in the switch transistor).&lt;/p&gt;

&lt;p&gt;
Your load regulation will be 1.5% which should be good enough for
most usages.&lt;/p&gt;

&lt;p&gt;
But this is only valid if you by 200mA meant short-circuit
current, and didn&amp;#39;t mean max current at nominal load (which would be
120 ohm and not 8000 ohm).&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: AC square wave constant voltage</title><link>https://community.arm.com/thread/114010?ContentTypeID=1</link><pubDate>Wed, 11 Jun 2008 01:18:22 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:83664cb8-bc90-46e1-89fe-6851516c4470</guid><dc:creator>Andy Neil</dc:creator><description>&lt;p&gt;&lt;p&gt;
... we could also ask whether this is really AC - ie
&lt;i&gt;&lt;b&gt;alternating&lt;/b&gt;&lt;/i&gt; - or is it just pulsed DC?&lt;/p&gt;

&lt;p&gt;
ie, does the voltage swing between +24V and -24V (or +/-12V), or
is it just 0V and 24V?&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: AC square wave constant voltage</title><link>https://community.arm.com/thread/100743?ContentTypeID=1</link><pubDate>Wed, 11 Jun 2008 01:14:46 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:f0e2231b-753c-48c8-af32-b46f184f84b5</guid><dc:creator>Andy Neil</dc:creator><description>&lt;p&gt;&lt;p&gt;
&lt;i&gt;&amp;quot;Doesn&amp;#39;t AC stand for Alternating Current? Which would imply
alternating (and therefore not constant) voltage.&amp;quot;&lt;/i&gt;&lt;/p&gt;

&lt;p&gt;
Maybe he means constant &lt;i&gt;&lt;b&gt;amplitude&lt;/b&gt;&lt;/i&gt;?&lt;/p&gt;

&lt;p&gt;
I don&amp;#39;t think it&amp;#39;s unusual to speak of a &amp;quot;constant amplitude&amp;quot; AC
source as &amp;quot;constant voltage&amp;quot; - even if, as you say, it isn&amp;#39;t
&lt;i&gt;literally&lt;/i&gt; true?&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: AC square wave constant voltage</title><link>https://community.arm.com/thread/76375?ContentTypeID=1</link><pubDate>Wed, 11 Jun 2008 00:51:41 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:b77ffc9c-144a-4bcf-86b2-5ea853db9d12</guid><dc:creator>Silly Sasuage</dc:creator><description>&lt;p&gt;&lt;p&gt;
I may be being dim here, but ...&lt;/p&gt;

&lt;p&gt;
Doesn&amp;#39;t AC stand for Alternating Current? Which would imply
alternating (and therefore not constant) voltage.&lt;/p&gt;

&lt;p&gt;
A constant voltage would normally be referred to as DC.&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: AC square wave constant voltage</title><link>https://community.arm.com/thread/51835?ContentTypeID=1</link><pubDate>Wed, 11 Jun 2008 00:24:25 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:e126110e-490a-4a00-a2b9-3f1ae37aed0f</guid><dc:creator>ImPer Westermark</dc:creator><description>&lt;p&gt;&lt;p&gt;
This is not a hardware forum.&lt;/p&gt;

&lt;p&gt;
Anyway: When the loads resistance is decreased, the current will
not drop - it will increase until you reach your rated maximum of
200mA. Then you will have to either shut off the output, or drop the
voltage (current regulation) or let the generator burn to
cinders.&lt;/p&gt;

&lt;p&gt;
Your specification only specify &amp;quot;with short circuit protection&amp;quot; so
it isn&amp;#39;t obvious if it should decrease the voltage or just disconnect
the load.&lt;/p&gt;

&lt;p&gt;
Don&amp;#39;t you mean that the frequency must be &lt;b&gt;variable&lt;/b&gt; between
100Hz and 100kHz?&lt;/p&gt;

&lt;p&gt;
Further: You call it a &amp;quot;&lt;b&gt;AC&lt;/b&gt; square wave constant voltage
generator&amp;quot;. Does that mean that it should generate +/- 24V (or maybe
+/- 12V), i.e. that it should switch polarity? Switching between 0V
and +24V is not AC. It is just pulsed DC.&lt;/p&gt;

&lt;p&gt;
Finaly: you require 200mA output, but specify max load 8000 ohm.
Max load is expected to be the lowest resistance that may be used.
24V / 8000 ohm means 3mA which is way less than 200mA. Did you really
mean that the max load should be 8000 ohm or did you mean that the
minimum load is 8000 ohm, i.e. that the load may vary between 120 ohm
and 8000 ohm?&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item></channel></rss>