Archive for January, 2010

First launch of the Easy Star – not so easy

Finaly the day came when weather conditions allowed to test my new Easy Star floater. There was no wind at all, temperature below -8C. First of all I’ve tried to launch without the camera. To keep conter of the gravity where it supposed to be, I’ve mounted metal plate in the nose of the plane. It was very difficult to launch the model. If I slowly hand launch the model, it drops on the ground. If I through it faster, the nose climbs up, stalls and falls down. Giving a motor more thrust doesn’t help either. Motor pushes the model towards ground also. (I suspect that motor is mounted too high and this is not a behaviour by design). Once I’ve managed to lift off, I’ve realized that rudder control is inverted. So I had to come back. The rudder is to little for this model. When it slowly glides it’s almost impossible to control it. I need to give more thrust to control it, so it odd situation when you need to increase speed to land correctly. I’ll need to mod this thing. I’m not sure about the ailerons. Maybe there is no need for them when the rudder will work properly. Anyway, I was astonished how good this plane floats. Even travelling decent distance, it lost almost no height. Here is my flight:

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Camera modding for servo-less aerial photography

To do aerial photos without servo motor, I need to electricaly connect push button on the camera to the receiver. Receiver outputs PWM signal, which, imho, by mistake is called PPM (RF modulation type). This PWM signal is 50Hz impulses, which width varies from 1 ms to 2 ms. It needs to be converted to logical 1 or 0. If impulse is > 1.5 ms, it should be treated as logical 1. There are plenty of schematics with 555 timer, or mircrocontroller. I’m going to use attiny 8 pin mircrocontroller, because it won’t require additional adjustment and is quite small. It can do autonomous periodic photo taking. I’ll write about this stage later (I’ll update this post or create new one).

If you want to take a picture, you need to press button half way (fist switch is activated). Then camera does autofocusing. When the picture is clear, you press button to the end and picture is taken. So I’ll do 1-2 second pause between pushes, which should give enough time for camera to focus. I’ve dissasembled my Canon SD600, and soldered wires to the button pins. I had to solder on plastic plate very carefully, because you never know how much heat resistant it is. I didn’t manage to solder wires to battery pins, because it’s deep inside in the camera under 2-3 PCB’s. So I’ll need to make battery shaped connector or fly with original battery.

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Assembling Easy Star

Finally I’ve bought Easy Star! It’s the most important day in my FPV career :) . This model is a living legend, made by Multiplex. It quickly became most favorable model among modelists, because it has pusher motor, very strong ELAPOR material and nice look. There are many mods for this model: ailerons, bigger rudder, brushless motor etc. I’ve bought FC2830-9T 1290KV 56g “Outrunner” motor, which was recommended by salesman, but right now I think it was a bad decision. 5″ propeller rotates to slow to have any thrust. I hope tri-blade 6″ will make a difference. If the motor is in it’s default place, you can’t fit anything bigger than 6″. I’ve found in the forums, that 2000-2700 KV motors should be used in this model. It you ever decide do go brushles, choose something from that range. The time will show if I’ll be able to fly with 1290 KV. I’ve mounted my A123 LiFePO4 battery with separated cells, because I wanted to center the mass correctly. I’ll mount 150g camera in the front, so I wanted to move as much weight as I can to the back. Manual recommends to make CG exactly 37 mm from the front side of the wing.
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Flygint at -15C

It was perfect weather outside, so we’ve decided to see how it feels to fly during very cold weather. It was -15-16C (about 5F). The place was reluctant to fly higher because it was heavy overloaded and the motor thrust too low. We are still waiting for bigger props from China. LiFePO4 batteries, so called A123 was working perfect, but camera’s LiPo battery was freezed after 3 minutes flight. After that camera shut off. I had to leave my control cabin (laptop covered with shirt) and land manually. Unfortunally there is no video footage from the landing part :)

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