Diode used with Relay

[whazza22]

Can anyone tell me what the result would be if a diode was put in the opposite way round in a bed light relay? (e.g. a bed head light for a hospital bed)

In the correct terminals but the black stripe on the diode in the wrong way. And its in the extra low voltage side.

 

[stef]

Can anyone tell me what the result would be if a diode was put in the opposite way round in a bed light relay? (e.g. a bed head light for a hospital bed)

In the correct terminals but the black stripe on the diode in the wrong way. And its in the extra low voltage side.

Probably a short circuit. The diode on the relay is to short out the negative voltage spike generated
by the de-energizing relay coil (the moment when the supply to the coil is off). If + is connected to the anode
then the diode is conductive.

 

[spider]

Virtually a dead short would be created, a fuse would hopefully of failed before any control circuit switch welded closed.

 

[whazza22]

Even oof its extra low voltage and functioning correctly?

 

[spider]

Even oof its extra low voltage and functioning correctly?

Hi,

If the diode is connected across the coil terminals with incorrect polarity, the relay would not energise as the diode would be the path of least resistance, (google blocking diode or flywheel diode).


It might well be a zener diode Zener diode - Wikipedia, the free encyclopedia as nothing else would be in circuit and still work, not seen one used in this way though.