During the last post, we had a quick look at including some diagnostic indicators to a circuit Today we will apply this to a circuit that could be used in a pump application. You will note in this circuit that I have used quite a few relays.
The first relay you will note is in your stop/start section. You would normally go from your control section to the contactor coil instead of a relay. What I am doing here is to set the starting sequence via the relay and then we will have and indication lamp telling us that the System has been turned On
The next relay you will see is connected via the Emergency Stop. When the emergency stop is “healthy” the relay will be energised. When the E Stop is pushed, the relay will drop out and we will get an indication: Emergency Stop Fault
Once started, the normally open contact of R1 will close the circuit to the contactor via a normally closed contact of Timer 1. This timer is energised at the same time as the contactor. Should the pump run and sufficient flow is created, the flow switch will close before the timer times out and the contactor remains energised
Should there not be sufficient flow by the time the timer has timed out, the pump will be turned off and we will have an indication of Low Flow. Have a look at the sketch below and see if it makes sense to you.
Again, in order for the sketch to be displayed clearly, click on it and it will open a larger view of it.
In the next post we will have a look at a more complex circuit diagram and I will show you what method I use to follow the circuit. Untill then, please always put safety first and do not take chances.