Why need to place this diode in this motor circuit?

[NicholasTok]

snubber diode motor

Hi everyone,

I have come across a circuit configuration which of a vibrator motor circuit.

I would like to ask one question, why is there a need to place a 1N4004 snubber diode across the emitter and collector?

I would like to know the analogy by placing the snubber diode and am I'm right to say that the transistor used for this configuration is a NPN diode?

**broken link removed**

please enlighten me.

Regards,
Nicholas Tok

 

[Old Nick]

https://en.wikipedia.org/wiki/Snubber

 

[barrybear]

It is an NPN transistor ( the control device). A diode is a diode and only a diode it is a pn junction ( in its native form).
The diode is used to divert high pulses that could cause a breakdown of the transistor junctions , often a diode is also placed acros the motor conduting spikes away from the collector to the supply rail.

 

[FvM]

The shown diode circuit seems meaningless, apart from the special case, that the motor is externally driven with no supply, respectively the motor keeps rotating due to inertia and the supply is shut down. In this case it would protect the transistor.

It's not what wikipedia calls a diode snubber, usually known as freewheeling diode.