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| The following is an overview of the Castle Creations Phoenix-35 Electronic
Speed Control and it's functionality. The Phoenix-35 is a Electronic Speed Controller designed for use in applications that will draw up to 35 amps. In this regard it is ideal for use in the T-Rex where some of the higher powered motors have amp draws in the 26-30amp range. The Phoenix-35 has a number of options that can be configured either using the usual beeps and throttle stick position method or by use of a clever little device called the PHX-Link. The latter option also allows for the automatic update of the speed controllers internal software to the latest level. This allows the ESC to be kept up to date with the latest developments and new software capability to be added as it is developed. The ESC contains a BEC which for the purposes of a T-Rex on a 3S pack is capable of running 4 micro servos and a receiver/gyro. The BEC should not be used to run 4 standard servos, particularly digital servos as it is not powerful enough when running from an 11.1v pack. This is not something of concern for T-Rex owners :) If using a 4S configuration or more then the BEC should be disabled and an external BEC must be used. Firstly let's go through the functionality of the ESC, the pictures below from the PHX-Link program show the various programmable options, and below that is a table showing the settings within each option. |
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| The items highlighted in red are my recommended settings for use of this
speed controller in the T-Rex. Let's run through these options one at a time : Cutoff Voltage This is the voltage level at which the ESC will go into it's cutoff procedure. This will either be a hard cutoff or soft cutoff depending on what you set for the cutoff type. For a 3S lipo 9 volts is what most people set. However I use the custom settings and set 8.8v as I have noticed that under full load lipos will occasionally drop to below 9 volts and I don't want to go into cutoff procedure in the middle of a high load maneuver. It's worth mentioning that Castle Creations have just introduced an automatic cutoff mode which senses how many cells are present and sets the cutoff appropriately for lipo's. The ESC when initiating beeps the number of cells detected. Of course you must have a fully charged pack for this function to work correctly, using a partially charged pack could cause the ESC to sense the wrong number of cells. Personally I time all my flights so I never hit the cutoff voltage but it is good to know it is there should I miss my transmitter alarm going off. Cutoff Type Hard cutoff just cuts the power to the motor immediately. So if you don't mind suddenly having to do an autorotation because you flew for a bit too long then this could be the option for you. Hmm, I don't think so. The correct setting is for a soft cutoff which will throttle down the motor and give you opportunity to do a powered landing......much better. Brake Type Last time I checked my T-Rex didn't have a brake, so disabled would be the best option here. Throttle Type OK there are several possibilities here. Autocalibrating will allow you to run an ordinary throttle curve ie. no governor. This mode means having to setup throttle and pitch curves from your transmitter to get the right headspeed and throttle to pitch loading. This mode isn't recommended for helicopter use. Fixed throttle mode is the same as autocalibrating in terms of running your own pitch/thorttle curves but can be used for helicopters. Governor High is for high RPM motors and gives finer governor control at high RPM. This would be the default mode for the majority of pilots. This lets you set the headspeed using the castle creations governor using throttle curve settings in your transmitter. In general you would have a 'normal' curve of something like 0 85 85 85 85. The 85 being whatever value gives you your desired headspeed, lower values = lower head speed and vice versa. To set 'idle up' you just go for a straight throttle curve e.g. 85 85 85 85 85. Governor low is for finer control at lower RPM and to be honest I can't think of a motor that fits the T-Rex that you would use for this mode to work correctly. Soft Start This controls how quickly the ESC will power up your motor. Fast start tends to be a bit too violent a start and will likely cause the machine to spin on it's skids due to the torque as you open the throttle. Softest is too slow in that if you close the throttle to lose height you may not be able to get the power back on quick enough when you open the throttle again to transition to a hover. I normally use the soft start option which is a good compromise between the hard fast and softest options. Motor Timing This option causes much debate but in reality it doesn't matter what you set as the ESC will sense the best settings for your motor and use that regardless of what you set manually. Current Limiting Again a debatable option, I've taken to using insensitive as it protects the ESC from power spikes but nothing more. So I don't have to worry about what current draws my motors put through the ESC. Other acceptable options are standard or disabled. Bear in mind that disabled offers no protection to over current (ie. you are open to frying your ESC due to a power spike or short out). PWM Frequency 111khz is recommended for brushless motors and is the default. OK, so that is all the setup options, so how does it perform. Performance/Flight Testing I will try the ESC in two throttle modes, auto calibrating and governor high mode. This is the only setting that changes the way the ESC behaves in flight. I have been experimenting with governor high mode. So far the performance has been flawless across the Mega and AON motors. Headspeed is easily set using the throttle curve and the governor does a good job of consistently trying to maintain that headspeed despite collective or cyclic changes. I am very pleased with the governor mode as it has taken all the headache out of trying to balance throttle and pitch curves without bogging the motor down too much. It also lets me set the exact headspeed I want, which is great given that overspeeding the head can cause the carbon blades to fly out of track. The ESC soft start is also very nice and spools the heli up at a nice steady pace without causing the tail to kick due to the torque change. This is in stark contrast to the Align 35A ESC which always kicked the heli through 90 degrees, even when using soft start. One of the often asked questions is how to setup governor mode. This is really very straight forward. The governor works on the basis that at any given throttle setting (say 90%) whatever the motor RPM is at that throttle setting the governor will try to maintain it for any pitch setting on the main blades, tail rotor inputs or cyclic loading. This means you can effectively forget about matching throttle and pitch curves and allow the governor to do this for you in real time. An example of the pitch curves you might set is given below based upon a 90% throttle setting giving you your desired 2400 RPM head speed. The 95% setting giving 2500 RPM for 3D. |
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| Fixed throttle mode is used if you want to use your own pitch / throttle
curves instead of the governor. Given that the governor works so well I
don't know why anyone would want to use this but I have come across reports
of motor combinations that appear to not work well in governor mode. Castle
Creations are always very keen to hear of such reports and normally fix
the problem with a software update which can be installed using the PHX-Link. Conclusion The Phoenix-35 has performed faultlessly across four different motors and various battery combinations. I have been particularly pleased with the governor mode which does a good job of controlling the headspeed through different pitch loadings. The Phoenix-35 is highly configurable to different user requirements and Castle Creations continually update the software with new revisions, sometimes adding new functions (such as the recent auto lipo detection facility). I recommend the use of this ESC, it is reasonably priced, high enough specification to handle any motor you might chose to use in the T-Rex and it performs to specification. The ESC doesn't appear to generate a lot of RF noise or get particularly hot during operation and as such I can't claim that it introduces any glitching to the radio system. I think this is the 'standard' for the T-Rex sized Micro Helicopter to which other ESCs must match or beat in order to be competitive. |
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