I need something faster than an ordinary relay .The point is that I used a relay to switch for external battery that power the circuit when the main supply goes off.
And this small delay while switching sometimes caused the registers of my microcontroller to be reset so i need a solution.

thanks.

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YOu can just use a transistor or solid state relay. HOwever, what you get in switching speed you trade for by giving up the ideal open and closed switch, which is what you get with a relay. If you cannot tolerate the leakage currents, then perhaps connect a LARGE decoupling capacitor to supply power to your circuit while the relay is turning on and to supress the effects of the bouncing of the contact when it closes. (YOu should have an extra large capacitor anyways, even with a semiconductor switch).

 

Why have a relay or a switch at all? Just combine the two power sources with suitable diodes and whichever one is at the higher potential will power the processor.

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Could you clarify more?!
thanks.

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He means put one diode in series with the battery -> circuit and another one in series with the main power -> circuit. THat way the battery won't charge the circuit and the circuit won't charge the battery, but whatever voltage is higher will feed into the circuit.

ANother way to say it is to make a Y connection between the positive power connection of your main power, battery, and circuit, then add a diode onto the positive battery connector and another one to the main power connector.

 

yeah.so the higher voltage would supply the circuit cause the common cathode could have only one voltage value.

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