|Mar 07, 2014, 10:28 AM|
Joined Mar 2014
Boosting the motor power on Hubsan X4 controllers
Hi, this is my first post on this forum. Hope someone will find it useful.
About a year ago, before Hubsan released models H107C and H107D I've tried to use X4 H107 FC as a platform for my indoor FPV Frankenquad. Motors and arms were from Walkera infra. I found that hubsan FC has superior flight characteristics, much better than number of Walkera and WLtoys FCs I've tried, but has the lack in power. Flight was possible but only with near full throttle. My first thought was that MOSFETs have too high internal resistance. I changed MOSFETs but this improved thrust only slightly. Almost accidentally I've found that if additional external P-type SMD MOSFETs are used instead of replacing original N-ones, great improvement in motor power may be achieved (intention was only to avoid replacement of N-types). Even better, with changing the value of gate pull down external resistor, it is possible to tune the max motor power. I recommend values from 150 to 390 ohms (I am using 150 and 220). Higher values produce more power. Seems that the internal MOSFET resistance wasn't the problem, it is the PWM pulse width. Change in pull down resistor value influences switch on threshold and consequently pulse width (never checked this with oscilloscope).
Because in the meantime Hubsan released H107D and H107C I was hesitant to post my finding. I'm using H107C now as an indoor FPV platform and it is fantastic, no need for this mod any more. Thanks to Midelic and his Hubsan module it has even better control and precision. Recently I tried to convert V929 for FPV by changing the stock FC (without autoleveling) with the H107C FC and found that it is short in power again. I applied my mod and it has a lot of power now.
The problem with this mod is that is only applicable to Frankenquads since there is no room in original Hubsan X4 shells for extra components. For stock Hubsans H107C and H107D it is not needed anyway since both have enough power for their weight.
Here is the (simple) schematics, sorry for hand drawing. Only one motor connection is shown since they are all identical.
I am using TSM2311 P-MOSFET, 20V, 4A found in my local shop. I have not tried, but this one is probably good enough as well:
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