Quote:
Originally Posted by RyanN
I still like the old 883s, and for just a little less tolerance, I would still like to see the 883s back in the robots. They are rated for more, and I think that's the best thing about them.
|
Ryan,
Don't be fooled by the spec sheet. There are many improvements in the 884 that make it a great device. The FETs in the 884 are rated at 64 amps each so in parallel they can handle continuous 130 amps easy. Remember that the Chalupa motors were not part of the kit when the 883 was available. The small motor is rated at 129 amps in stall. You can fudge the specs a little since the FETs have no heatsink but do have a fan and are only reguired to supply current intermittantly over a two minute match. Heatrise in the devices is the more critical event in using these little wonders. (derate the 64 amps to 45 at 100 degrees C) For most cases there is no problem.
With today's technology, even manufacturing defects are rare. The vast majority of failures I have been able to inspect have turned out to be user induced. i.e. metal shavings, a foreign body contacting the tabs of the FETs or continuous driving with an inefficient drive train. As I have pointed out in many threads before, tank style driving produces incredible loads on the motors when turning, near or at stall for the motors. By far and away, I have seen more smoke in a turn (or pushing in a turn) then at any other time.