RC-Monster Forums - View Single Post - What is this BS Castle is feeding this customer?

BrianG · 02:23 PM

Can't really raise the switching frequency too much for a couple reasons; FETs may not have the slew rate to support higher frequencies, and motor inductance can play a big role as to how effective this would be.

Back-EMF voltage spikes can certainly cause issues with possibly more sensitive components of the BEC. But I would think that as long as these spikes are at or under the 6s-7s limit, it should be fine. So, why not install a transorb, diode, or whatever to clamp the spikes at no higher than say 30v. That would give some headroom for 18 NiMH cells (because they can peak as high as ~1.5v right after a charge), yet shunt potentially damaging spikes to ground protecting the BEC circuits.

Makes me think Castle should have just made the MMM an Opto ESC, or put a circuit based off the typical LM2596 IC (which has a 40v and 3A rating)....

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BrianG RC-Monster Admin Offline Posts: 14,609 Join Date: Nov 2005 Location: Des Moines, IA	05.14.2008, 02:21 PM Can't really raise the switching frequency too much for a couple reasons; FETs may not have the slew rate to support higher frequencies, and motor inductance can play a big role as to how effective this would be. Back-EMF voltage spikes can certainly cause issues with possibly more sensitive components of the BEC. But I would think that as long as these spikes are at or under the 6s-7s limit, it should be fine. So, why not install a transorb, diode, or whatever to clamp the spikes at no higher than say 30v. That would give some headroom for 18 NiMH cells (because they can peak as high as ~1.5v right after a charge), yet shunt potentially damaging spikes to ground protecting the BEC circuits. Makes me think Castle should have just made the MMM an Opto ESC, or put a circuit based off the typical LM2596 IC (which has a 40v and 3A rating).... Last edited by BrianG; 05.14.2008 at 02:23 PM.