[SOLVED] Circuit power control

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YoSuk

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Hello,

I am currently working on a project where i want to be able to turn on and off the power to three circuits from a microcontroller/button switch. These are low power circuits where the total current wont exceed 600mA. Is it possible to do this with a transistor as shown in this picture? Or do i have to use relays or some other method? I want the circuit to be as small and use as little current as possible.



Thank you for your help,
Ole K.
 

That will work, the main problem is that when the transistor is switched it will exhibit a common impedance between the three circuits. Also make sure that the transistor is truly saturated, Ib = Ic/10.
Frank
 
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    YoSuk

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Thank you for your reply! What is the best way to address the problem of common impedance? The distance between the circuits and the ground will be very short, probably between 5-10cm of copper trace, since the circuit will be on a PCB. Will this have any effect?

Thanks again,
Ole K.
 

When the transistor is hard on, .2V @ 10 mA, this gives a resistance of .2/.02 =10 ohms. Which will then have a small voltage across it from each circuit, which may cause interference. One way is to use three transistors, each with its own base resistor and fire the "on" signal to all three base resistors, which then turn on their respective transistors.
Frank
 
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    YoSuk

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Hi,

Try for solid state relays
http://www.futurlec.com/Relays/SSRDIP60Vpr.shtml
http://www.datasheetdir.com/VO14642AT+Solid-State-Relays
 
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    YoSuk

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Thank you both for your replies. I will try with the SSR.

Regards,
Ole K.
 

A logic level power-MOSFET will work good as switch with only a few mili-ohm on-resistance..
 

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