http://www.batterybackupguide.com/blog/i-want-to-use-a-capacitor-for-an-alarm-clock-but-am-not-completey-sure-on-what-size-to-use/ Thu, 17 May 2012 22:31:39 +0000 http://wordpress.org/?v=2.7 hourly 1 http://www.batterybackupguide.com/blog/i-want-to-use-a-capacitor-for-an-alarm-clock-but-am-not-completey-sure-on-what-size-to-use/comment-page-1/#comment-478 pingerlee Tue, 20 Jan 2009 01:02:15 +0000 http://www.batterybackupguide.com/blog/i-want-to-use-a-capacitor-for-an-alarm-clock-but-am-not-completey-sure-on-what-size-to-use/#comment-478 well, charge in cap = voltage x value of cap, so value of cap = charge / voltage. You want the charge to last 3 sec, and charge = current x time, so cap value = (0.2Ax3sec)/10v=0.06F, which is a large cap. Remember that you can use smaller caps in parallel if this is too large. well, charge in cap = voltage x value of cap, so value of cap = charge / voltage. You want the charge to last 3 sec, and charge = current x time, so cap value = (0.2Ax3sec)/10v=0.06F, which is a large cap. Remember that you can use smaller caps in parallel if this is too large.

]]> http://www.batterybackupguide.com/blog/i-want-to-use-a-capacitor-for-an-alarm-clock-but-am-not-completey-sure-on-what-size-to-use/comment-page-1/#comment-477 some_yank Fri, 16 Jan 2009 18:11:40 +0000 http://www.batterybackupguide.com/blog/i-want-to-use-a-capacitor-for-an-alarm-clock-but-am-not-completey-sure-on-what-size-to-use/#comment-477 Better check your math first. If e= 120v and r = 50, you then have a 2.5 amp alarm clock....don't think so. Once you know the true current consumption, you just need to calculate the capacitive time constant. Better check your math first. If e= 120v and r = 50, you then have a 2.5 amp alarm clock….don’t think so. Once you know the true current consumption, you just need to calculate the capacitive time constant.

]]> http://www.batterybackupguide.com/blog/i-want-to-use-a-capacitor-for-an-alarm-clock-but-am-not-completey-sure-on-what-size-to-use/comment-page-1/#comment-476 oldguy Thu, 15 Jan 2009 14:00:48 +0000 http://www.batterybackupguide.com/blog/i-want-to-use-a-capacitor-for-an-alarm-clock-but-am-not-completey-sure-on-what-size-to-use/#comment-476 use yor RC time constant formula to determine how long the cap's charge need to last to keep the clock powered and if a series resistor is needed to control the discharge use yor RC time constant formula to determine how long the cap’s charge need to last to keep the clock powered and if a series resistor is needed to control the discharge

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