At 08:52 PM 17/10/2009, you wrote:
>Hi,
>
>I found this schematic on the internet
>http://farm3.static.flickr.com/2682/4020964908_49fb1cd20a.jpg
>
>I want to drive a 24 VDC motor with a PIC. The manufacturer
>says the motor is a 12vdc to 36 vdc. I measured the stall
>current at ~10 Amps. Anyway I built the cicuit above using
>IRFU5505 for the P Channel Mosfet and a BUZ101S for the N
>channel. Right now I am just using a 5 volt supply thru
>200 ohm resistors to substitute for the pic logic pins and a
>12volt 12 amp battery charger to power the motor. Any way when I
>stall the motor using the above circuit it stalls at 4.5
>amps. It seems like I am losing power in the circuit ?  If I
>stall it hooked directly to the battery charger it stalls at 10
>Amps. Any suggestions ? I am going to be driving a pretty heavy
>load so I need all the power I can get.
>
>BUZ101S Vds 55V, Vgs 2-4V, Ciss 500pf, Id 22A, Idm 88A,
>Rds .05 Ohms
>http://www.datasheetcatalog.org/datasheet/siemens/BUZ101S.pdf
>
>
>IRFU5505 Vds -55 Vgs -2to-4V, Ciss 650pf, Id -18A, Idm -64A,
>Rds .11 Ohms
>http://www.datasheetcatalog.org/datasheet/irf/irfr5505.pdf
>
>Thanks,
>Kevin

You are only driving the n-channel MOSFET partly on with 5V. It is
spec'd at 10V Vgs. You will find that the BUZ101S parts are getting
very hot very fast.

You can either increase the drive voltage or use a better suited
(eg. logic level) type of n-channel MOSFET.


>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com



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