tag:blogger.com,1999:blog-71729133582669132382011-07-30T15:50:12.611-07:00The Past dayhttp://www.blogger.com/profile/12531664881508792781noreply@blogger.comBlogger51100tag:blogger.com,1999:blog-7172913358266913238.post-74734635395873621352009-11-30T22:38:00.000-08:002009-11-30T22:41:01.163-08:00This simple circuit sounds a beeper when its electrodes detect water. It is powered by a single 1.5v N cell. A small 1.5v button battery will also work.<br /><br /><a href="http://2.bp.blogspot.com/_ZQcyIDLbx30/SxS6L5QYb1I/AAAAAAAAABY/6pS41X2boWE/s1600/WATER+SEEPAGE+ALARM.GIF"><img id="BLOGGER_PHOTO_ID_5410153765889666898" style="DISPLAY: block; MARGIN: 0px auto 10px; WIDTH: 400px; CURSOR: hand; HEIGHT: 299px; TEXT-ALIGN: center" alt="" src="http://2.bp.blogspot.com/_ZQcyIDLbx30/SxS6L5QYb1I/AAAAAAAAABY/6pS41X2boWE/s400/WATER+SEEPAGE+ALARM.GIF" border="0" /></a> More Detail <a href="http://www.discovercircuits.com/PDF-FILES/h2oalm.pdf">discovercircuits.com</a><br /><div></div><div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/7172913358266913238-7473463539587362135?l=alarm-circuits.blogspot.com' alt='' /></div>The Past dayhttp://www.blogger.com/profile/12531664881508792781noreply@blogger.com0tag:blogger.com,1999:blog-7172913358266913238.post-84683368312227130342009-11-30T22:34:00.000-08:002009-11-30T22:37:06.266-08:00Many companies offer simple alarm devices for personal use in bedrooms or hotel rooms. A metal chain attached to a box holding the electronics is placed around the inside doorknob of a wood door. Anyone grabbing the knob from the outside is detected by the electrical capacitance change that occurs from the human hand contact between the knob and the box.<br /><br /><a href="http://1.bp.blogspot.com/_ZQcyIDLbx30/SxS5PN0W_PI/AAAAAAAAABQ/POSPgNOcaUQ/s1600/DOORKNOB+ALARM.GIF"><img id="BLOGGER_PHOTO_ID_5410152723437255922" style="DISPLAY: block; MARGIN: 0px auto 10px; WIDTH: 400px; CURSOR: hand; HEIGHT: 229px; TEXT-ALIGN: center" alt="" src="http://1.bp.blogspot.com/_ZQcyIDLbx30/SxS5PN0W_PI/AAAAAAAAABQ/POSPgNOcaUQ/s400/DOORKNOB+ALARM.GIF" border="0" /></a><br /><div>lmost all of the commercial devices sold use a more expensive and power consuming radio frequency circuit approach to detect the capacitance change. But, a very inexpensive and micro power technique can also work. </div><div> </div><div>This circuit schematic should dramatically reduce the cost of the device and allows it to operate for many years from one set of batteries. </div><div>More detail <a href="http://www.discovercircuits.com/PDF-FILES/dooralm2.pdf">discovercircuits.com</a></div><div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/7172913358266913238-8468336831222713034?l=alarm-circuits.blogspot.com' alt='' /></div>The Past dayhttp://www.blogger.com/profile/12531664881508792781noreply@blogger.com0tag:blogger.com,1999:blog-7172913358266913238.post-55518071394268551002009-11-30T22:29:00.000-08:002009-11-30T22:33:33.658-08:00For some medical equipment it is important for an operator when power is lost to the machine.<br /><a href="http://4.bp.blogspot.com/_ZQcyIDLbx30/SxS4KgWTAKI/AAAAAAAAABI/3KR3n_A_j5Q/s1600/MACHINE+POWER+LOSS+BEEPER.GIF"><img id="BLOGGER_PHOTO_ID_5410151543000465570" style="DISPLAY: block; MARGIN: 0px auto 10px; WIDTH: 400px; CURSOR: hand; HEIGHT: 181px; TEXT-ALIGN: center" alt="" src="http://4.bp.blogspot.com/_ZQcyIDLbx30/SxS4KgWTAKI/AAAAAAAAABI/3KR3n_A_j5Q/s400/MACHINE+POWER+LOSS+BEEPER.GIF" border="0" /></a> The beeper is powered from a 9v battery and requires the machine to have a power switch with a third set of contacts.<br /><div>More Detail Please see <a href="http://www.discovercircuits.com/PDF-FILES/powerlos.pdf">discovercircuits.com</a></div><div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/7172913358266913238-5551807139426855100?l=alarm-circuits.blogspot.com' alt='' /></div>The Past dayhttp://www.blogger.com/profile/12531664881508792781noreply@blogger.com0tag:blogger.com,1999:blog-7172913358266913238.post-85967482443791947972009-11-30T22:22:00.000-08:002009-11-30T22:25:07.850-08:00This circuit produces a short beep once each minute. It is powered directly off the 120vac power line to remind you that a device connected to the circuit is turned on.<br /><br /><a href="http://4.bp.blogspot.com/_ZQcyIDLbx30/SxS2jo4LUII/AAAAAAAAABA/BwAffmsTqlo/s1600/POWER+REMINDER+BEEPER.GIF"><img id="BLOGGER_PHOTO_ID_5410149775763525762" style="DISPLAY: block; MARGIN: 0px auto 10px; WIDTH: 400px; CURSOR: hand; HEIGHT: 248px; TEXT-ALIGN: center" alt="" src="http://4.bp.blogspot.com/_ZQcyIDLbx30/SxS2jo4LUII/AAAAAAAAABA/BwAffmsTqlo/s400/POWER+REMINDER+BEEPER.GIF" border="0" /></a><br /><div>It is simple enough to be packaged inside a small plastic box. It might be ideal for computers, printers or some test equipment that shouldn't be left on all night.</div><div>More detail <a href="http://www.discovercircuits.com/PDF-FILES/beeper2.pdf">http://www.discovercircuits.com/PDF-FILES/beeper2.pdf</a></div><div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/7172913358266913238-8596748244379194797?l=alarm-circuits.blogspot.com' alt='' /></div>The Past dayhttp://www.blogger.com/profile/12531664881508792781noreply@blogger.com0tag:blogger.com,1999:blog-7172913358266913238.post-17260111070654262652009-11-30T22:12:00.000-08:002009-11-30T22:15:32.649-08:00The circuit is powered for years by a single 3 volt lithium battery. It sounds an alarm when the temperature exceeds a certain point. With some minor changes the circuit could also be configured for an under temperature (freeze) alarm.<br /><a href="http://1.bp.blogspot.com/_ZQcyIDLbx30/SxS0PATSOlI/AAAAAAAAAA4/O2HJHvhZ-18/s1600/MICRO+POWER+OVER-TEMPERATURE+ALARM.GIF"><img id="BLOGGER_PHOTO_ID_5410147222250732114" style="DISPLAY: block; MARGIN: 0px auto 10px; WIDTH: 400px; CURSOR: hand; HEIGHT: 234px; TEXT-ALIGN: center" alt="" src="http://1.bp.blogspot.com/_ZQcyIDLbx30/SxS0PATSOlI/AAAAAAAAAA4/O2HJHvhZ-18/s400/MICRO+POWER+OVER-TEMPERATURE+ALARM.GIF" border="0" /></a>The circuit uses a cheap but accurate thermistor as the temperature sensor.<br />More Detail<br /><a href="http://www.discovercircuits.com/PDF-FILES/overtemp.pdf">http://www.discovercircuits.com/PDF-FILES/overtemp.pdf</a><div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/7172913358266913238-1726011107065426265?l=alarm-circuits.blogspot.com' alt='' /></div>The Past dayhttp://www.blogger.com/profile/12531664881508792781noreply@blogger.com0