Join Date: Aug 2005
Location: Orangeville, Ontario, Canada
Generic relay test, whether contact arrangements are N.O. normally open or N.C. normally closed. The normally condition usually refers to when there is no power to the relay, when the relay sits there doing nothing.
Relays have a component that enables them to operate and use springs or gravity to make them go back to their normal state. If power is required to operate them both ways the relay has two coil assemblies in then 1 to close the armature, 2 to open the armature, but usual relays operate with power on an armature coil to magnetically pull the relay in to operate the contact.
Contact arrangement is built in so that a N.C. contact opens and a N.O. contact closes. Some relays operate their prospective contacts all at the same time or make some contacts change their state early while others change state later.
Some relays are built to operate with time, so some are on-delay and some are off -delay.
On delay---A delay takes place upon the relay activation at some future time.
Off delay---Relay is energized or de-energized and at a future time the off set of contacts work.
With all this in mind the testing and verifying of a relay requires that you the operator knows what type of relay you have. But with electric coil type relays the coil becomes an electromagnet and needs a ferrous metal to magnetize;the magnetic properties cause the attraction of metal to the electromagnet and then the contacts move from one position to the other.
Contacts must be in good shape, not welded shut, not blown apart.
The relay must be able to freely move the movable parts to the fixed part.
The contacts cannot touch each other, nor should the attached wires
Wired contacts need to be secure, frayed wires are no good
Plug in style relays must make good contact to their matching plugs
Covered relays must not interfere with relay operation
Relays draw 3x the current to draw in and settle down upon magnetically sealing
Some relays are wired with holding contacts so when they are energized they remain in, these types have a stop button to de-energize them.
Relays can be powered from the same source or from a secondary source
Relays can operate large currents or small currents
These are electro-mechanical devices that have their counterparts in electronic devices that wok similarly but are considered solid state because they do not have moving parts but they do have moving electrons.
Hope this helps with troubleshooting those pesky relays