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Hello, I'm currently building a system with a rechargeable battery in it. The power supply is 12v dc 3a and the battery is 12v 5mah. The battery is NiMH, it cannot discharge below 10v, if i do so i'll ruin it. I would like to design a circuit where, when i'm using the power supply the battery stop supplying and when I unplug it the battery takes over. Also, I want the battery to stop supplying if its voltage is below 10v . I would like to use IC 741 as a comparator. I really need help. Thanks in advance! |
April 15, 2017 |
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There is a type of power plug that does just this. When you plug in your power supply the battery is mechanically disconnected and when you pull out the plug your battery is switched on again. Here is one that does 12V 3A: The battery low voltage cutout is fairly simple to arrange, but remember the circuit itself will draw a few mA from the battery when it is off. A typical circuit is here: http://www.homemade-circuits.com/2013/10/low-battery-cut-off-with-indicator.html To minimise battery current when off you need a low current opamp, like this: You will need a different values of R1 and R2. |
by mikerogerswsm April 15, 2017 |
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PS - here's a similar power connector in use: http://mike-wsm.org.uk/psv.html Note the battery negative is switched (centre pin positive). |
April 15, 2017 |
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