efficiency of the ev3 H-bridges ?

[HaWe]

hiya,
are there already details about the ev3 H-bridges?
I have to drive at least 4 motors for my Tetrix tread chassis (in pairs of 2 at each side). If the motor outputs are powerful enough then I would appreciate to plug 2 of them together to 1 motor port each (only black-black and white-white flexes of course), but I wouldn't like to always trigger the built-in fuses.

[philoo]

As far as I know the EV3 motor driving chip is the same as the one used in PF receiver V2 (while NXT one was the same as V1). This makes this comparison somewhat releveant: http://philohome.com/pfrec/pfrec.htm. As with PF V2 the real power limitation will probably be EV3 input resettable fuse - and I don't know yet its characteristics.

[HaWe]

so, in few words, would you recommend to try 2x2 large-ev3--motors at 2x1 ev3 port or would you discourage to do that?

[philoo]

Depends on the load! clearly the "official" method would be to use another EV3 in slave mode. Anyway I'm fairly confident that you can try without burning anything...

[HaWe]

the load is always at the limit of the motor thermal fuses. I probably even will need 2-4 addional motors but there is no daisy chaining and no support of the MS RCX-MMux yet by BCC/C .

[philoo]

the load is always at the limit of the motor thermal fuses. I probably even will need 2-4 addional motors but there is no daisy chaining and no support of the MS RCX-MMux yet by BCC/C .

Then I think EV3 input fuse will trigger... NXT one was a 1.8A fuse, hopefully on the EV3 with its 4 motors ports it was upgraded to 4/3*1.8=2.4A (except if some regulatory issue forced lower value!) - Or maybe they used separate fusing for motor ports??? But I have no clue about this...

[HaWe]

ev3 Input fuse?
or EV3 OUTput fuse?

[philoo]

Input. I mean the fuse between the battery compartment and the EV3 main board. There is no output fuses on motor ports, but the driver chip does limit current to about 3A (and it has a thermal shutdown too if needed).

[HaWe]

aah, I see.
so you mean overall 3A for all and everything?
then I definitely would need 1 daisy-chained EV3 for each couple of motors or an ev3 driver for the MS MMux which got an external power supply.

[gloomyandy]

It looks to me like there are two separate thermal fuses one for each of the two motor driver chips (Outputs AB and CD). Not sure what current they trigger at though....