free wheeeling diode help?

[Shreehari]

Hello
My ARM Board consists of digital outputs.In their document they had given that"user has to add proper free wheeling diodes across inductive loadsto protect the output transistors against high voltage".

What I have to now to get the output?what are freewheeling diodes?

Thanks

 

[IanP]

Flyback diode (sometimes called a snubber diode,
freewheeling diode, suppressor diode, or catch diode) is
a diode used to eliminate flyback, the sudden voltage spike
seen across an inductive load when its supply voltage is
suddenly reduced or removed ..
see:
https://everything2.com/title/flywheel+diode

I don’t know your ARM board, but mu guess is that it has some Open-Collector (digital) on/off outputs that can sink a couple of hundreds of mA, so a load (relay, bulb, LED) can be connected between Vcc and the output pin ..
Find out in the data sheet what the max sinking current is, and never connect a load that may require more current that the output can handle ..

IanP

 

[Shreehari]

it is written that max output current is 0 - 5A.What s the value of load that I should connect?

 

[IanP]

According to your information, anything up to 5A ..
The data sheet should also specify voltage limits, so keep that in mind too ..

IanP

 

[cameo_2007]

I need a clarification in this,

how is the path of that free wheeling current ?
Is it towards the power source or will it be circulating within the loop of Inductor and the diode until it discharges to zero ?

 

[Shreehari]

When the current flow to an inductor (and an AC induction motor certainly is one) is suddenly interrupted, the inductor tries to maintain
the current by reversing polarity and increasing the voltage. Without the "freewheeling diode" the voltage can go high enough to damage the
switching device (IGBT, Thyristor, etc.). With it, the reverse current is allowed to flow through the diode and dissipate.

 

[cameo_2007]

through the diode and dissipate.

through diode to where is my question?

 

[Shreehari]

might be towards the power source..

 

[cameo_2007]

are you sure ?

 

[Shreehari]

quiet sure..do u have any arguments to prove it wrong?

 

[cameo_2007]

NO. I am not into any arguments.
The thing is i dont know.

So say, for eg:- the source is a regulator (eg LM7812)
U mean the free wheeling current flows to the output pin of the regulator? and then ?

 

[monnoliv]

If you put your free wheeling diode (D) across the inductor (L), the free wheeling current will never go back to the source, it only "turns" in the L-D circuit until vanishing due to dissipation inside D and L.

 

[cameo_2007]

well said i guess

 

[Shreehari]

Monnoliv s answer seems to be correct

 

[sherazi]

Monnoliv is correct,

the reason of fly back is to provide it a circular path, so that current passes through it and dissipates off through the components , and it never goes back to the source...