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Topic: low voltage cutout switch/relay to prevent killing batteries?? (Read 6039 times) previous topic - next topic

lemming

#15
Jun 10, 2014, 04:21 am Last Edit: Jun 10, 2014, 05:17 am by lemming Reason: 1
OK, I get it now. It gets a bit more complex though.

You can read up on linear vs switched mode regulators but to cut to the chase you need to conserve battery power so you need to bypass the inefficient linear mode regulator on the arduino board. Instead you will use a switched mode regulator that puts out 5 volts and feed this into the 5 volt pins on the Arduino. Below is a cheap and suitable regulator that i have used in the past but similar units would be fine.

http://www.digikey.com/product-detail/en/OKI-78SR-5%2F1.5-W36-C/811-2196-5-ND/2259781

Due to the required low drop-out voltage required for the fob plus its (assumed) low current draw, you would be best off using a cheap and simple 12 volt zenner diode/resistor combination to power that. The problem with that is that it will draw a few milliamps even when the fob is not activated. A workaround  may be to permanently close the push button and then use the relay to switch power to the fob (through the zenner regulator) as no power used unless activated . You would need to check if this works first.

The other way is to use a very low  dropout DC-DC buck converter but they may not put out 12 volts when their input is close to 12 v. Alternatively you could use a buck-boost converter so that you always get 12 volts as long as the input voltage is above ~3 volts.

e.g.  http://www.ebay.com/itm/DC-DC-Converter-Regulator-Step-up-Step-down-2-in-1-/370538642812






allermuller

#16
Jun 10, 2014, 08:04 am Last Edit: Jun 16, 2014, 05:27 am by allermuller Reason: 1
TC54VC2102EZB is really good ?? In fact, I have been looking for such a device, for my husband, can you inform more information? Beacause i have no idea ?the electronics...thank you  :smiley-red:

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Ulli

Did you know that there are special chips called "supervisors"? Simply look here: https://www.google.de/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=automotive+supervisor+battery+-jobs+-plant
I would prefer the LTC2960 from LT. It's current consumption is below 1µA... In general, you also have to consider the self-discharging effect of a battery which is several times more. More Information is  to be found here: http://batteryuniversity.com/learn/article/elevating_self_discharge
As i know LT, you shurely will get free samples at http://www.linear.com/samples/LTC2960
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lemming

Quote

can you inform more information?


http://www.microchip.com/wwwproducts/Devices.aspx?product=TC54

http://www.digikey.com.au/product-search/en?vendor=0&keywords=TC54VC4302EZB

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