using servo amplifier as ESC

[oldman]

Hi Everyone;

I've been using an old modified servo as a ESC.

I lost my notes on it and can't read the number on the
mosfet, I build this one 3 or 4 years ago. I was
gonna build one for a friend and would like to use
newer mosfets. A ten amp should be fine as he plans
to start flying slow/park flyers. I have a BEC for it on
my bread board, as soon as I'm sure the BEC is reliable
I'll post it if there is any interest.

Thanks

Frank

[Bruce Abbott]

The best deal I know of is the GF4410 (only 84 cents at Mouser (http://www.mouser.com/), stock number 625-GF4410), rated at 10A so should be good for up to 5A continuous for a Speed 280 motor. It's a surface-mount chip, so could be a bit fiddly to install, but would make for a very compact unit. Other good smd FETs include the FDS6680 (11A), BSO301 (13A) and IRF7455 (15A at 2.8V gate drive!).

For Speed300 or Speed400 motors you need a higher current rating. You could wire two GF4410's in parallel, or use a more conventional TO220 packaged unit such as the IRL2203 or HUF76143 (which can easily handle 15A continuous).

Note that an ESC made from a servo driver operates at frame rate (50Hz) which causes more motor heating and poor efficiency at part throttle. It can be pretty rough on small motors.

[oldman]

Bruce;

Thanks for the info. I mainly use mine on my bench, but
a friend saw it and wants one for a temp. until he can get
a high rate unit store bought unit, as they are quick and easy.

Frank