Re: [PSUBS-MAILIST] Re: Motor controller...

[Subscuba@aol.com]

Laurent, I copied your post and can answer some of your questions below.

Ken Martindale


> Hi John,
> I started working on your schematic and I have a few
> questions for you:
> - Why did you add extra flyback diodes , the IXFK
> serie already have some in their package?


All Power Fets have body diodes which can be used but there are difficulties with body diode recovery times and I didn't want to deal with the potential destructive effects of using the body diodes.

> - Is there any specific reason why you used a H bridge
> with only N-channel Mosfet instead of both N and
> P-channel Mosfet?


I cannot get P channel FETs to handle the currents involved.

> - I have some concerns about the heat sink dimensions.
> Are you currently using the hull of your sub to cool
> them? :-)
> -I was also interrested in using Minn Kota motors. Do
> you have any specs on these? Are you already using
> them? 
> I plan to use 4 of them (2 for the main prop and 2 for
> up/down & left/right) but i'm still working on the
> mechanical design so I still don't know what are my
> power requirements. Looks like I'll be very close to
> Ken's needs.
>
> Laurent