Re: Camtronics and Sanyo-Denki Review

At 10:31 PM 11/8/2000 -0800, you wrote:

>Thanks for the great and informative post, Mike! Now I'm drooling. I've
>got Dan's 2A board and three Sherline 110/134 oz-in motors and a 24V, 8A
>power supply (switcher) from Marlin P. Jones ( http://www.mpja.com ) on
>order for my Sherline mill.
>
>I'll plan on providing a heatsink as you suggest. Have you built a duct
>around your board/heatsink, or are you just blowing air onto the heatsink?

It depends on your heatsink(s) and enclosure but ducting probably isn't
necessary. Just try to get a decent extruded heat sink on the L298s with
as much surface area as possible and point the fan at it (bringing in
"outside" air). I kept mine fairly low to the board and it's actually
resting on the diodes and resistors to help take some of the stress off the
L298 leads.

Also, you may need to add an output filter capacitor to your switcher if
you get any weird problems. Mount the capacitor as close to the controller
board as possible. I'd also suggest fusing the power to each of the 3
output sections with 2 amp fuses (or one 6 amp fuse for all 3 if you want
to save a few bucks). The fuse(s) may or may not save the L298s if you
short one of the motor leads (or a motor fails) but they can't hurt. CNC
with metal chips flying everywhere can be a rather "harsh" environment.

Lastly, you could use a power resistor to drop some of the voltage to feed
the onboard 5 volt regulator if you want to run the entire controller off
the 24 volt supply. The ideal value would be 60 - 75 ohms at 10 watts. Be
sure and mount it safely as it will run quite hot (but well within its rating).