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I'm building a digital clock using 40xx series IC's. Currently you just plug it in and it's on. Are there any major drawbacks or disadvantages to not having an on/off switch?

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    \$\begingroup\$ The main issue is about how long it takes for the power supply to come up to a steady, useful value versus how the circuit behaves during the period prior to a stable voltage. It can be helpful to have a switch of some kind, if you arrange things so that the switch leaves the power supply enabled and operating but only resets the circuitry depending upon that supply. And only then, if the circuit is sensitive to the timing of the power supply "ramp up" period. Often, though, folks just arrange an RC delay (or some other kind of delay) so that the circuit isn't engaged until the supply is up. \$\endgroup\$ – jonk Jan 10 at 6:04
  • \$\begingroup\$ It is wiser to use a wallwort and coaxial DC plug for these. Most people do this so the safety issues are external . Now the plug acts as a switch. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jan 10 at 8:04
  • \$\begingroup\$ I think the question is whether or not an ON/OFF switch is recommended on a device as opposed to just plugging it into the wall socket. \$\endgroup\$ – Transistor Jan 10 at 8:29
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Are there any major drawbacks or disadvantages to not having an on/off switch?

Depends on what you think is 'major'.

If the circuit is mains powered then it should be designed to start up reliably even if 'turned on' by simply plugging it in. This may require a more sophisticated reset circuit to ensure that sequential logic is properly initialized when the power supply voltage rises slowly or erratically.

Another drawback that might be considered 'major' is if the device is battery powered, since you would have to disconnect the battery to turn it off. Some mains powered clocks use a 9V battery to keep the timing going during power cuts. If you unplug the clock for a long time and forget to disconnect the battery it will go flat.

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  • \$\begingroup\$ My circuit seems to work perfectly fine whether switched on or plugged in. I’d like to know if there are any electrical inconsistencies to the “plug it in” method. If there is a risk of damaging the circuit would be a major one. \$\endgroup\$ – StrugglingStudent117 Jan 10 at 17:31
  • \$\begingroup\$ You haven't shown us your circuit, so how could we know? If it is properly designed it should not be damaged by plugging it in. \$\endgroup\$ – Bruce Abbott Jan 10 at 17:48

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