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Old Feb 16, 2007, 06:22 PM
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San Jose, California
Joined Oct 2004
870 Posts
Dave,

Need a litle more info to help you.

You mean the "hinge acts" that have a thin PCB attached to the coil and another attached to the magnet, with tape hinges between the PCBs?

Which Plantraco RX? The "Butterfly" RX (5mm spaced battery magnets) or the larger 0.9g RX (10mm spaced magnets)?

The Butterfly RX has no FETs to drive low-ohm actuator loads, the 0.9g RX does.

The hinge acts are about 150 ohm each (suitable for the Butterfly RX), the "remote" acts (with pivoting magnet and pushrod arm) are near 50 ohms (suitable for the 0.9g RX).

Mark
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Old Feb 16, 2007, 11:49 PM
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United States, CA, Riverside
Joined Feb 2003
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Details

Okay I am home now and able to give more details.

I have the .9gm 3 channel hfx900 system.

The hinge acts that I hope to use are the 150 ohm (I just measured them) BIRD type.

I am going to try these even though they may be a bit light. Since I am going with true EDF power using only 6mm motors I need to go as absolutely light as possible.

So which way do you figure I can wire these up? Series or parallel?

Thanks in advance for your help fellows.
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Old Feb 16, 2007, 11:57 PM
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Cardington,Ohio
Joined Nov 2006
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If you put them in parallel, your resistance will then be 75 ohms. (R1 xR2) divided by (R1 plus R2). its easy when both r's are the same; just divide by 2 .
will that burn up your RX ? Maybe someone can tell you the minimum resistance for that Rx
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Old Feb 17, 2007, 12:35 AM
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San Jose, California
Joined Oct 2004
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The 0.9g 3chan RX handles 50 ohm actuators, no problem. So a 75 ohm load (hinge acts in parallel) is fine.

6mm EDFs? Cool.

Mark
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Old Feb 17, 2007, 02:41 PM
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Okay very helpful. Now I am going to assume that a parallel set up is more powerful than series.......right? I will plan to post a pic of the project here when finished.

Thanks again.
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Old Feb 17, 2007, 03:02 PM
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San Jose, California
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Each act will receive the same current that it would receive if there was only one act. So, individually, they won't be more powerful. Its just that the RX can deliver the total current to drive both. You'll still have relatively low torque from those hinge acts. Keep the size of the control surfaces reasonable.

If your plane will be flying fast, it might be hard for the hinge acts to overcome the force of the wind flowing over the surfaces. About how big is your plane and how heavy, overall?

Mark
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Old Feb 17, 2007, 05:49 PM
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Yes, I am concerned about that. My weight goal is 27 gm maximum, wing area 180 sq. cm. I have little experience building with foam (more of a stick and tissue guy). Most of the plane will be built from 1.3 mm depron. I am going way lighter than my head tells me I should on all the building steps. If I can come in a lot lighter than 27 gm- all the better. However, a slightly higher wing loading may not be such a bad thing since the EDF's require a certain amount of ram air pressure in order to reach maximum efficiency. Of course, the increased speed requires more torque from the act. The age old balancing act of modeling. I will go very conservative with the size of the rudders until I see how it performs in the air.
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