An electromagnetic relay is a mechanical device and therefore subject to wear and tear. Before installing it in the circuit, it must be checked. To carry out this operation, the equipment available to each home master is used.
Instructions
Step 1
Check out the relay pinout. First of all, find out where the winding leads are located. Also find the location of the terminals of the contact groups: normally open (which close when triggered) and normally closed (which open when triggered). If the relay documentation is in English, the phrase "normally open" means normally open contacts, "normally closed" means normally closed. The so-called changeover contacts can be represented in the form of two groups, one of which is normally open and the other normally closed, and which are combined at one of the terminals in such a way that their total number is reduced from four to three.
Step 2
If the pickup voltage of the relay is unknown, but only the pickup current is known, measure the coil resistance. Then multiply the measurement result by the pickup current (first converting both values into SI units), and you get the pickup voltage in volts. This test method is not applicable for relays with AC windings.
Step 3
If, in the course of the previous operation, you measured the resistance of the relay coil, you at the same time found out if the winding is intact. If you have not taken such a measurement yet, take it. During the measurement, do not touch the leads of the winding and probes of the ohmmeter, so as not to get hit by the self-induction voltage.
Step 4
Apply only AC voltage to the AC winding. Do not shunt it with a diode.
Step 5
Try applying DC voltage to the winding equal to the operate voltage. If the relay is good, it will trip. Also, do not touch the winding leads and source terminals for the same reason. It is useful to shunt the coil with a 1N4007 diode, connected in reverse polarity, but you must not reverse the polarity of the winding in order to avoid a short circuit. It is impossible to touch current-carrying circuits in the presence of a diode anyway, since it can fail at any time.
Step 6
Using an ohmmeter, check the condition of each contact group. When there is no voltage on the winding, normally open groups should be open, normally closed groups should be closed. When the stress is removed, the situation should be reversed.
