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Author Topic: [RQD]help with Pololu Pushbutton Power Switch LV  (Read 939 times)
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Wizpic
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« on: August 30, 2015, 11:32:03 23:32 »

I'm working on my milliohm meter and want to add an single push button for on then control it with auto off from the arduino  but the trouble is it runs off a3v battery (2x1.5v batteries)and then a step up converter to 5v and came across the Pololu Pushbutton Power Switch LV which works with 2.5v to 5.1v input, I can buy the mosfet used (FDS4465) but not sure how they do the latching circuit has can't find the rest of the schematic of that part (latching) anybody got any ideas about how they do it, I think it's just a transistor to hold the gate on then turn off the transistor off to turn circuit off or is the a better way with low current draw
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bbarney
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« Reply #1 on: August 31, 2015, 12:15:43 00:15 »

http://www.eevblog.com/2012/03/30/eevblog-262-worlds-simplest-soft-latching-power-switch-circuit/

and  here http://www.eevblog.com/forum/projects/an-improvement-on-the-soft-latching-power-switch/
« Last Edit: August 31, 2015, 12:17:55 00:17 by bbarney » Logged

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CocaCola
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« Reply #2 on: August 31, 2015, 01:25:51 01:25 »

http://www.faqs.org/patents/app/20090237065

Or you can go to the real patent website and do a search for patent number 7,781,920

http://patft.uspto.gov/netahtml/PTO/search-bool.html

Click on the [images] button after you search to see the schematics...
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« Reply #3 on: August 31, 2015, 08:16:28 08:16 »

Barney I did see the first one but reading and playing with it on another project I found it was not good a bit hit n miss,did not see the second one looks good  but I want to be able to turn it off by the arduino will look more in detail at it may be I can add it.
Coca great find did not think about doing a patent search normally you don't find so much detail
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« Reply #4 on: September 01, 2015, 12:54:51 00:54 »

I am sure there are some SR-Latch made in SOT23 package.  that would definitely simplify the switching.

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« Reply #5 on: September 02, 2015, 02:10:24 02:10 »

Here is the schematic I use for the switching.
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« Reply #6 on: September 02, 2015, 04:58:15 04:58 »

... personally I like this one (very reliable): http://todbot.com/blog/2010/01/02/momentary-button-as-onoff-toggle-using-555/
-an
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« Reply #7 on: September 03, 2015, 04:05:18 16:05 »

@Parmin for an SR latch like that would you require some method of debouching the switch since you are pulsing the clock?
If so would a simple RC sufficient for that purpose?
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« Reply #8 on: September 04, 2015, 12:04:12 00:04 »

@Parmin for an SR latch like that would you require some method of debouching the switch since you are pulsing the clock?
If so would a simple RC sufficient for that purpose?

Yes
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