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| Assan AS-25A ESC | |||||||||||||||||||||||||||||||||||||||||
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| The following is an overview of the Assan 25A ESC and it's functionality. This speed controller is a very basic speed control in that it does not have a governor mode. However, it is one of the cheapest brushless speed controls on the market today and if it functions well could form a part of a budget setup. The speed control itself looks no different to any offering from Castle Creations having the standard motor connectors, battery connectors and receiver connector typical of any other speed control. I decided initially to test the speed control with a basic and docile motor. The motor I chose was the Aon 3000 KV which shouldn't put much strain on the speed control and should perform well within the 25 amp limit. Having installed all the equipment I fitted the lipo and proceeded to first spool up. I was advised by Assan that at initial spool up the motor may run a little rough as the speed control works out how best to work with the fitted motor. I didn't experience any rough running with the motor chosen and the spool up was nice and controlled as you would expect from any speed control in fixed throttle mode. The model was then lifted into the air and put through a straightforward flight of hovering maneuvers whilst I assured myself that everything was functioning correctly. At the end of the flight I checked the temperatures of the speed control and the motor. The speed control was not exhibiting any thermal problems but the motor did seem to be overly hot considering what I had asked of it. I fitted my second pack with a view to doing a flight of sport flying and also to give myself some more opportunity to open and close the throttle a lot more and get a good feel for the speed control. About four minutes into the second flight the model suddenly started to lose power, I landed briefly and then tried to take off again and experienced the same problem. Again I checked the temperatures of the speed control and motor, the motor did now appear to be extremely hot. The Aon series of motors do tend to run a little on the hot side and this is why Aon provide a full heatsink for their motors. I hadn't got the heatsink fitted at this particular time however I hadn't expected the motor to get this hot considering I wasn't really pushing it that hard. I was a little concerned that the speed control appeared to be making the motor run hot but I have the option of fitting a heatsink so I returned home to do this. This also gave me opportunity to recharge packs ready for the next flight session. I returned to the field later heatsink installed and hoping for no thermal issues this time around. Against the first pack I just perform hovering maneuvers and the second pack sport flying. The heatsink was definitely working and I got through both flights without any thermal issues halting proceedings. I wanted to try some more adventurous flying so I decided to change out the motor and fit the Aon 3500 KV. This time I would fit the heatsink right from the start. The next day I returned to the field once more to try out the more powerful motor on the speed control. I completed three packs with a fair amount of 3-D flight. The biggest problem by far was the head speed dropping during 3-D maneuvers, something I couldn't do a great deal about apart from applying some throttle collective mixing to try to keep head speed up. This was only partially successful. During this time I also carefully monitored the motor temperatures and again the motor did appear to be running hotter than I would normally expect. Some more investigation was definitely required. I decided to look into the assan the speed control configurations and also to understand exactly what settings should be used with Aon motors. The Aon is a two pole motor, by default the assan controller is setup for four pole motors. This could well explain the reason for my overheating motors. More testing was required so I reconfigured the assan controller for a two pole motor. This had the desired effect of reducing the temperature of the motor, so clearly reading the instructions is necessary (shock!!). The feature list for the ESC is fairly good considering the low price : High rate (10 KHz) switching (PWM) Six to twelve NiCd, Ni-MH cells or two to four Li-poly cells with receiver. Up to ten NiCd, Ni-MH cells or three Li-poly cells with three micro servos. Twelve NiCd, Ni-MH or four Li-poly cells MAX (with BEC disabled). Dynamic braking ensures prompt prop folding. BEC (2.0A) provides power to receiver and servos -eliminates separate receiver battery. Over temperature protection. User Programmable Features. Low-voltage protection - the value of low-voltage cutoff can be set. Cutoff can be programmed for motor stop or reduced power. Brake Type. Throttle Range. Timing Advance. Safe "power on" arming program ensures motor will not accidentally turn on. Low torque "soft start" prevents damage to fragile gearboxes. Auto shut down in 4sec after when signal is lost or radio interference becomes severe. Microprocessor controlled. Change the rotation by programming One thing not mentioned here is that the BEC on this ESC is 2A as opposed to the fairly standard 1.5A found on other more expensive ESC. The user manual is available online in PDF form and can be viewed here --> Assan PDF Manual Assan have also recently introduced PC programming capability for their range of ESC which is another function typically only seen on more expensive ESC. Let's go through the various functions of the ESC with some explanation of each function. The default values are marked in red. |
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| Clearly the low voltage setting MUST be changed for use in a T-Rex or pack
damage could occur due to over discharge. Motors tested with this ESC : |
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| Conclusion Overall the Assan ESC offers a functional speed control with a reasonable range of features. It doesn't offer governor control but this may not necessarily be an issue as many T-Rex fliers prefer to run on throttle curves due to some governors causing tail wag. Tests with two inrunners have been very good but the first test with an outrunner (JustGoFly 450F) was catastrophic. The test with the 450F resulted in the ESC bursting into flames almost immediately upon spool up. I would not recommend using this ESC with outrunners based on this experience. If you are looking for a ESC and on a tight budget then the Assan 25A does offer some good functionality at a very reasonable price. If you have this ESC rate it using the Trex Tuning rating system ..... |
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