weekly timer

electronic weekly timer 

When we want to control the exact time of activation and function of a power consumption that is repeated every week we can use the weekly timer. Similarly there daily timer and rarely monthly timer.
A simple weekly electronic timer shown in the photo.

The minimum period you can turn depends on the individual model. in one in photograph is one minute.
There are also mechanic timer that gets its name from the programming way, with teeth that get on or off and each tooth has a specific duration eg 15 minutes.

The standard is to contain an internal battery to keep time if it drops the power supply.

Bottom right, in this photography is to provide suply at 230 volts and below left is the contact we use for control. The supply voltage varied depending on the model and is electrically isolated (galvanically isolated) from contact consumption.
If  we have high power consumption is better to put intermediate relays. The timer in this case controls the armature of the relay and the relay controls the consumption.
Necessarily need intermediate relay if consumption is three phase or consisting of more than two single-phase differential phase.
There are popular in the market timers who come directly to schuko socket and control the consumption of their own place in the socket - outlet.