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When building a circuit, are there any conventions as to where the on/off switch should pe placed? As in between the negative pin of the battery and ground, or between the positive pin of the battery and circuit supply point?

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  • \$\begingroup\$ No, there are no conventions. If putting the switch in the wire connecting battery to ground does the job then so be it. Not all battery-powered circuits are grounded and those that are may have positive or negative terminals of the battery grounded. \$\endgroup\$
    – Andy aka
    Apr 25, 2015 at 17:35

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No, there are no conventions. If putting the switch in the wire connecting battery to ground does the job then so be it. Not all battery-powered circuits are grounded and, those that are, may have positive or negative terminals of the battery grounded. I'm mentioning this because the question assumed a negative ground.

If a battery powered circuit has a remote activation switch, quite a few designers would choose to use an NPN BJT or N channel MOSFET in the negative lead of the battery in order to activate it; the reason being that better "on" characteristics are obtainable for the same price.

I see no reason to justify always switching the ungrounded terminal of the battery on the basis that the circuit will "remain live". It's battery powered and like I said earlier, a lot of battery powered equipment is ungrounded.

However, lets explore the problem of switching the relevant battery terminal to ground to activate the circuit - until that switch is closed there can be no more risk of "stray" leakages, currents or voltages partially powering the circuit because the battery will have an open circuited terminal that isn't going anywhere by itself!

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You should place it between the positive terminal and the circuit supply, because if you place it between the negative and your circuit ground, even if the switch is open, you circuit is "live" because if anything else ground the circuit before the switch it will turn on.

Another way of saying it, placing it on the positive insulate you circuit from the battery power when the switch is open.

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one may put switch on any supply line which it is NOT grounded. If it is a floating circuit stray voltage may damage sensitive devices. prior to selection of grounding supply pl. ensure, especially with input instruments, power supply which supply terminal is grounded.. select the same polarityfor grounding your circuit and put the switch on the other polarity supply line.. vtingole

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