The idea is to generate an automatic starting mechanism for a home power
generator (not industrial).
I guess this could be done with a PLC, but this I think it would a very
expensive alternative, so I thought maybe, if it possible, the control
device could be replaced by Arduino.
I think to have defined the connection logic, but I would analyze and
translate this logic to the real model in which each component would be
physically connected with the intermediate elements necessary.
Then We would have the Arduino being fed by UPS, which receives line
voltage (220 V). When there is a power interruption, the UPS goes into
"Battery", feeding the Arduino, which controls at all times the line
voltage. If the voltage is zero, the power generator is activated.
In case of finding a value greater than zero, the generator is disabled.
The generator is also connected to the same power line to provide power
to the input of UPS. Here I am not sure whether an intermediate element
should be connected between the generator and the line to ensure that
the electrical current to flow only in the direction from the generator
to line if:
a) in the case when the power generator is turned off, the current
coming from the line in what would be the output of the power
generator could eventually cause damage.
b) in the case that the power supply is restored and during the interval
of time the generator is on, the meeting of the incoming stream of
the line with that provided by the generator could even cause some
damage to the electrical system.
Perhaps placing an electric device in the line before the generator is
connected to it, so as to interrupt the current from the line while the
generator is activated can avoid potential problems may occur by a) and
This whole issue is worth resolving if is there any way of connecting
the home power generator to the Arduino. As I was researching, those
generators without autostart, allow be turned on via a key or button. I
I don't know if it will come with another alternative mechanism. The
issue would be how to change this manual mechanism for a form where the
on/off is controlled by Arduino.
Moreover, to have a more complete control, also I thought Arduino
perform the monitoring of the load level on the tank. Here the issue is
where to put the sensor in the tank, in case really necessary that the
sensor is inside, as the tank should be always closed or clogged.
Although I read some time ago that there are sensors to measuring levels
from outside (capacitive sensors?). I think the further away the
electric sensor of the fuel, better for security.
This Arduino would be connected to a computer which monitoring through
Nagios  so that it sends a message about the state of tank level as
well if the generator is stared or not.
To completely automate this circuit and make the generator is turned
once a week, maybe I could develop a script that runs with crond on the
computer that is connected to the Arduino, so that the script sends a
start command to the generator during a short period of time at a
certain time a given day of the week for the generator starts by
maintenance, but well... this would be the icing on the cake
did not add this in the attached graph.
I was thinking the part that would make switching between the power line
and the generator. Also I attach this diagram to tell me if I am well
oriented. Beyond the general appreciation you can give me, I doubt if
the connection that I marked with the circle is well done.
Thanks in advance for your reply.