blown mosfet pmv31xn can i replace with alternative.?

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crazyflying
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blown mosfet pmv31xn can i replace with alternative.?

Post by crazyflying » Wed Nov 29, 2017 12:32 pm

like title i blew a pmv31xn on q4 mosfet for the motor.....
is it possible to replace with an alternative.
as i only seem to be able to find and order one from china...

i have loads of old helicotper and cheap drones i found in bins that use the AO3400A mosfet (xorb-48)

will that do.?

im not so savy myself...

just trying to not have to order anything and take parts from old stuff instead?

thanks



tobias
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Re: blown mosfet pmv31xn can i replace with alternative.?

Post by tobias » Thu Nov 30, 2017 10:04 am

The AO3400A looks like it will work just fine.

crazyflying
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Re: blown mosfet pmv31xn can i replace with alternative.?

Post by crazyflying » Thu Nov 30, 2017 3:34 pm

ok thanks i managed to find one from the rubbish pile...

tested and sadly seems there is a problem still...

i shorted the bat input..some how after doing big drones and using xt60s and such had no idea some battery manufactures cheange the positon of +n-.so thats what blew the mosfet...

now when i plug in the battery there is some very small movement when battery pluged in ..not like the usual 360º or 180º whatever it is...

if i try and start it up in cfclient it doesnt move at all...all the other 3 work fine...

id like some help how to diagnose the problem as there is no visual sign of another blow out so im wondering what could have happend shorting the bat??

i have tested the diode (d6) and its also dead so i will look for a new one but am also having trouble finding one in the uk...

i find this (http://uk.farnell.com/fairchild-semicon ... dp/1467516)
but it is 3 pin and i took the name bat54 from shematic and on the crazyflie its only a 2 pin diode...?

thanks again ciao

tobias
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Re: blown mosfet pmv31xn can i replace with alternative.?

Post by tobias » Thu Nov 30, 2017 3:37 pm

If the diode is shorted that is the kind of behavior I would expect. You can as a first thing just remove it and see if that works but not having it might ware the MOSFET so I would recommend having one there.

crazyflying
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Re: blown mosfet pmv31xn can i replace with alternative.?

Post by crazyflying » Thu Nov 30, 2017 4:43 pm

ok will do
remove it with a mini jump leed acros the diode?
thanks

tobias
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Re: blown mosfet pmv31xn can i replace with alternative.?

Post by tobias » Fri Dec 01, 2017 8:30 am

Just remove it as a first thing to test

crazyflying
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Re: blown mosfet pmv31xn can i replace with alternative.?

Post by crazyflying » Tue Dec 19, 2017 1:33 pm

so removed it it spins up fine....

used a turnigy 750 mah baterry that should work with its high c rating...

but so far it trys to fly but cant get of the ground ..

so im a bit sad and unsure where to go....

i have bought the original mosfets and can replace them back to normal..but in my head it should work as is.

i will try back with the small motors to see if its just a battery problem.

but i belive maybe something else has gone wrong....

so far all connects and runs to go into optic flow mode and hover but it can get enough umphh to take off...

thanks (*_*)>>>>>>

tobias
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Re: blown mosfet pmv31xn can i replace with alternative.?

Post by tobias » Wed Dec 20, 2017 8:15 am

I read on the forum that 750 mAh is on the edge of lifting of and if the flow is attached that might be just a bit too much. Have you increased the thrust to 99%? There is also a hack you can do as the thrust is limited in FW as well for regulation headroom. You might effect stability by doing that though. Also turning off battery compensated thrust could help.

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