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       <description>Free electronics circuits &amp; schematics!</description>
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          <item>
             <title>Fonera patch  version 0.2 released</title>
             <link>http://www.CircuitDB.com</link>
             <pubDate>Thu, 08 May 2008 16:09:06 +0200</pubDate>
             <guid><guid isPermaLink="false">news 20 at CircuiDB.com</guid></guid>
             <description><![CDATA[Today we released a new patch for the Fon firmware. We have included OpenVPN in the firmware so your Fonera can now act as an VPN server! <a href="http://www.circuitdb.com/articles/11/5" target="_blank" class="postlink">Download and read more here</a>.]]></description>
          </item>
          <item>
             <title>Tone Control Circuit</title>
             <link>http://www.CircuitDB.com/circuits/id/266</link>
             <pubDate>Sun, 04 May 2008 05:25:46 +0200</pubDate>
             <guid><guid>http://www.CircuitDB.com/circuits/id/266</guid></guid>
             <description><![CDATA[Based on the classic Baxendall tone control circuit, this provides a maximum cut and boost of around 10dB at 10K and 50Hz.
The first [url=http://www.chinaicmart.com/suppliers/174/BC109C.html]BC109C[/url] transistor (left hand side) is acting as a buffer. It provides the circuit with a high input impedance, around 250k has a voltage gain of slightly less than unity. As the Baxendall tone control circuit is a passive design, all audio frequencies are attenuated. The position of the controls and reactance of the capacitors alters the audio response. The last transistor provides a slight boost of about 3x. The output is designed to feed an amplifier with input impedance of 10k to 250k. Both tone controls should be linear type potentiometers.]]></description>
          </item>
          <item>
             <title>3 seconds to 2 minutes timer</title>
             <link>http://www.CircuitDB.com/circuits/id/265</link>
             <pubDate>Tue, 22 Apr 2008 08:33:02 +0200</pubDate>
             <guid><guid>http://www.CircuitDB.com/circuits/id/265</guid></guid>
             <description><![CDATA[This timer makes a LED be on for a certain amount of time after pressing the switch.
This time is adjustable from 3 seconds to 2 minutes using the potmeter.
Instead of a LED other load can be connected to this circuit, a relay for instance.

[url=http://www.circuitdb.com/download.php?fileID=217]TinyCAD file of this circuit[/url]]]></description>
          </item>
          <item>
             <title>Fun with La Fonera</title>
             <link>http://www.CircuitDB.com/articles/11</link>
             <pubDate>Mon, 21 Apr 2008 23:03:18 +0200</pubDate>
             <guid><guid>http://www.CircuitDB.com/articles/11</guid></guid>
             <description><![CDATA[Building a serial port interface. Mount network shares. Build your own modifed firmware for La Fonera while keeping the original Fonera functionality. ]]></description>
          </item>
          <item>
             <title>And the winner is.....</title>
             <link>http://www.CircuitDB.com</link>
             <pubDate>Mon, 31 Mar 2008 13:12:53 +0200</pubDate>
             <guid><guid isPermaLink="false">news 19 at CircuiDB.com</guid></guid>
             <description><![CDATA[CircuitDB is proud to announce that <a href="http://www.circuitdb.com/profile.php?mode=viewprofile&u=369" target="_blank" class="postlink">saurabhparashar</a> is the winner of the <a href="http://www.circuitdb.com/contest/" target="_blank" class="postlink">CircuitDB Design Contest 2008!</a> He sent in his <a href="http://www.circuitdb.com/circuits/id/234" target="_blank" class="postlink">Programmable path navigator Robot project</a>. Congratulations saurabhparashar! You win 100 US dollar and eternal fame!]]></description>
          </item>
          <item>
             <title>New WiiKey firmware (1.9S) available</title>
             <link>http://www.CircuitDB.com</link>
             <pubDate>Wed, 26 Mar 2008 23:46:49 +0100</pubDate>
             <guid><guid isPermaLink="false">news 18 at CircuiDB.com</guid></guid>
             <description><![CDATA[Here is some good news for WiiKey owners, <a href="http://wiikey.cn" target="_blank" class="postlink">http://wiikey.cn</a> is up again! They also have released an update that should fix the problem with original Super Smash Bros Brawl disc and add a DVD update blocker to prevent a NTSC disc to ruin your PAL Wii.


Just to be sure CircuitDB will continue hosting the files <a href="http://www.circuitdb.com/articles/8" target="_blank" class="postlink">here</a>.]]></description>
          </item>
          <item>
             <title>Quick Draw</title>
             <link>http://www.CircuitDB.com/circuits/id/264</link>
             <pubDate>Thu, 28 Feb 2008 12:51:31 +0100</pubDate>
             <guid><guid>http://www.CircuitDB.com/circuits/id/264</guid></guid>
             <description><![CDATA[The object of Quick Draw is to test your reaction time against your opponent's. A third person acts as a referee and begins the duel by pressing S1, which lights LED1. Upon seeing LED1 go on, you try to outdraw your opponent by moving S2 from &quot;Holster&quot; position to &quot;Draw&quot; position before your opponent moves S3 from &quot;Holster&quot; to &quot;Draw&quot; position. Who ever gets there first will light the corresponding LED and will automatically prevent the other LED from lighting, clearly indicating a winner.

Copyright 2001 [url=http://home.maine.rr.com/randylinscott/index.html]Randy Linscott[/url]]]></description>
          </item>
          <item>
             <title>Touch 'N Flip</title>
             <link>http://www.CircuitDB.com/circuits/id/263</link>
             <pubDate>Tue, 26 Feb 2008 09:05:50 +0100</pubDate>
             <guid><guid>http://www.CircuitDB.com/circuits/id/263</guid></guid>
             <description><![CDATA[This circuit will give you a feel for how the touch plate works in a circuit and you can expand on the circuit to suit your project needs. The touch plate can be a small piece of metal or aluminum foil. Start the circuit by moving S2 to the set position and then back to the previous position. Now press S1. One of the LED's will light. Now touch the touch plate and the LED's will flip on the opposite way. The sensitivity of the plate will vary depending on the humidity. Adjust the VR and capacitor that is connected to S2 to adjust the sensitivity.

Copyright 2001 [url=http://home.maine.rr.com/randylinscott/index.html]Randy Linscott[/url]]]></description>
          </item>
          <item>
             <title>Automotive Speed Indicator</title>
             <link>http://www.CircuitDB.com/circuits/id/262</link>
             <pubDate>Sun, 24 Feb 2008 18:02:35 +0100</pubDate>
             <guid><guid>http://www.CircuitDB.com/circuits/id/262</guid></guid>
             <description><![CDATA[The speed of an automobile can be indicated by detecting the pulses generated by the ignition system and causing an LED to light. The circuit utilizes a quad NOR gate IC chip. Two of the gates are configured as a one shot multivibrator which produces a fixed duration pulse each time the primary circuit of the automobile ignition system opens the circuit to the ignition coil. The other 2 gates are used as buffers which provide an accurate rectangle pulse. As the number of pulses per second increases, the voltage fed to the base of of the NPN transistor becomes high enough to cause it to conduct and turn on the LED. The speed at which the LED lights is set by R4. The input of the circuit is connected to the distributor side of the ignition coil or to the tachometer connection on those cars that are equipped with electronic ignition.

Copyright 2001 [url=http://home.maine.rr.com/randylinscott/index.html]Randy Linscott[/url]]]></description>
          </item>
          <item>
             <title>American police car siren</title>
             <link>http://www.CircuitDB.com/circuits/id/261</link>
             <pubDate>Fri, 22 Feb 2008 08:19:53 +0100</pubDate>
             <guid><guid>http://www.CircuitDB.com/circuits/id/261</guid></guid>
             <description><![CDATA[This circuit simulates the siren of an American police car. It uses two 555 timers in the circuit. The 555 on the right is wired as an alarm tone generator and the second 555 timer on the left is wired as a low frequency astable timer which generates a ramp waveform of about 6 seconds that is buffered by the transistor and again used to frequency modulate the tone generator. The transistor is used to help strengthen the signal to the speaker.

Copyright 2001 [url=http://home.maine.rr.com/randylinscott/index.html]Randy Linscott[/url]]]></description>
          </item>
          <item>
             <title>Star Trek "Red Alert" siren</title>
             <link>http://www.CircuitDB.com/circuits/id/260</link>
             <pubDate>Wed, 20 Feb 2008 06:55:45 +0100</pubDate>
             <guid><guid>http://www.CircuitDB.com/circuits/id/260</guid></guid>
             <description><![CDATA[This circuit simulates the &quot;Red Alert&quot; siren from the TV show Star Trek. It uses two 555 timers in the circuit. The 555 on the right is wired as an alarm tone generator and the second 555 timer on the left is wired as a 1.5 second non-symmetrical astable that generates a fast rising but slow falling saw tooth waveform. This waveform is buffered by the transistor and used to frequency modulate the tone generator and making its frequency rise slowly during the falling parts of the saw tooth but collapse rapidly during the rising part of the saw tooth. The output starts as a low frequency, rises for 1.15 seconds to a high tone, ceases for .35 seconds and then repeats the cycle.

Copyright 2001 [url=http://home.maine.rr.com/randylinscott/index.html]Randy Linscott[/url]]]></description>
          </item>
          <item>
             <title>British police car siren</title>
             <link>http://www.CircuitDB.com/circuits/id/259</link>
             <pubDate>Tue, 19 Feb 2008 21:32:14 +0100</pubDate>
             <guid><guid>http://www.CircuitDB.com/circuits/id/259</guid></guid>
             <description><![CDATA[This circuit simulates the siren of a British police car. It uses two 555 timers in the circuit. The 555 on the right is wired as an alarm tone generator and the second 555 timer on the left is a 1 Hz astable multivibrater. The output of the left timer is to frequency modulate the right timer. This causes the right timers frequency to alternate between 440Hz and 550Hz at a 1 Hz cyclic rate. The transistor is used to help strengthen the signal to the speaker.

Copyright 2001 [url=http://home.maine.rr.com/randylinscott/index.html]Randy Linscott[/url]]]></description>
          </item>
          <item>
             <title>12 Volt to 120 Volt Inverter</title>
             <link>http://www.CircuitDB.com/circuits/id/258</link>
             <pubDate>Sat, 09 Feb 2008 07:53:03 +0100</pubDate>
             <guid><guid>http://www.CircuitDB.com/circuits/id/258</guid></guid>
             <description><![CDATA[Ever needed a low power 120volt AC  power source for your car, van or truck? Well this circuit should do the trick for you. It will supply 15 watts of AC power to a device. It should power lamps, shavers, small stereos and small appliances. If you draw to much power the circuit will shut down all by itself. The output of this circuit is a square wave so there may be some noticeable hum on audio units plugged into it. To reduce some of the hum increase the value of the output capacitor which is at .47uf now. That transistor in the circuit are high power PNP transistors. Radio Shack part number 276-2025 are good ones to use or TIP32. The transformer is a 24 volt 2 amp center tapped secondary Radio Shack part number 273-1512 or equivalent.

Copyright 2001 [url=http://home.maine.rr.com/randylinscott/index.html]Randy Linscott[/url]]]></description>
          </item>
          <item>
             <title>Voice Record / Playback Circuit</title>
             <link>http://www.CircuitDB.com/circuits/id/257</link>
             <pubDate>Fri, 08 Feb 2008 11:32:56 +0100</pubDate>
             <guid><guid>http://www.CircuitDB.com/circuits/id/257</guid></guid>
             <description><![CDATA[The ISD1000A is a Direct Analog Storage  device which allows you to store 20 seconds worth of voice data on an IC chip which can be play backed anytime. The data stored will stay in memory even if the power is removed. To use the circuit below simple apply power to the circuit, press the record button and hold. Speak clearly into the microphone. You have up to 20 seconds of voice message that you can store. If you talk beyond that time the chip will only store the first 20 seconds. After recording, release the record button. To playback the message, press the playback message and the message you recorded will play back. The microphone is an electret mic and the speaker is a 8 ohm speaker. If you use a 16 ohm speaker then the 10 ohm resistor marked optional, can be eliminated. This circuit can be the basis of many other larger projects. For example it could be part of an alarm circuit which plays back a voice warning when the alarm circuit is triggered.

Copyright 2000 [url=http://home.maine.rr.com/randylinscott/index.html]Randy Linscott[/url]]]></description>
          </item>
          <item>
             <title>Plant Moisture Meter</title>
             <link>http://www.CircuitDB.com/circuits/id/256</link>
             <pubDate>Thu, 07 Feb 2008 21:51:32 +0100</pubDate>
             <guid><guid>http://www.CircuitDB.com/circuits/id/256</guid></guid>
             <description><![CDATA[Stick the metal probes into a freshly watered plant and adjust R5 for a mid-scale meter deflection. The meter will monitor the soil wetness and the meter will indicate whether it is to moist or to dry. This circuit uses a dual power supply which could be created by two 9 volt batteries.

Copyright 2000 [url=http://home.maine.rr.com/randylinscott/index.html]Randy Linscott[/url]]]></description>
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