On 14/04/2011 18:13, Olin Lathrop wrote:
> V G wrote:
>> Hey all, instead of using a wire wound resistor for testing battery
>> drain, I'm thinking of using a heat sink bound MOSFET and control the
>> drain-source current with the gate. I'm looking to get around a 0.5 -
>> 2 ohm resistance between drain and source. Is this possible?
> Sure it's possible, but will require active control and feedback else you=
'll
> have no idea what is actually going on.  The easiest is probably a low si=
de
> current sense resistor with a opamp driving the gate to keep the voltage
> accross the resistor at the desired level.
>

Plenty of examples out there for this type of circuit - there is a=20
reasonable video on making the above on EEVBlog:
http://bit.ly/dmxNQ5
Do remember that (as Spehro mentioned) many MOSFETs are not designed for=20
linear mode - check the datasheet and look at the Safe Operating Area=20
graph - it should have various pulse widths down to (hopefully) DC, pick=20
one that has the curves you need for DC, preferably with ample headroom.=20
Also remember to calculate thermal resistance correctly and use the=20
right heatsink - as it happens there is another tutorial on EEVBlog=20
about this:
http://bit.ly/b3EOck


--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.