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I just started flying helos last summer - an impulse purchase - but have been enjoying the snot out of them so far. If you want to really learn your radio, then pick up a used 450 over on RunRyder or HeliFreak and learn to hover!!
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Anyway . . . here's how the governor (or Fixed RPM) mode works on the Castle ESC.
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Using the CC Link software, you select three RPM's that you want the ESC to hold for you. You also enter the gear ratio (we'd use 1:1) and number of poles and KV of your motor. The software will then calculate if you have enough "headroom" to maintain the selected RPM. "Headroom" is how much extra throttle - margin - the ESC has to maintain the selected RPM during times of increased load.
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Once the CC Link software has determined that the ESC is capable of meeting your demands, it will let you write those RPM's to the ESC. Your three RPM's will be in boxes labelled 30%, 70%, and 100%. You can also set the spoolup time and transition between RPM's. There is also a way to set a much faster spoolup speed from 0% throttle using the "Autorotation Bailout" function.
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Now your throttle is no longer a throttle, but an RPM selection channel. When the throttle channel is at either 0%, slightly above 0% (when using Auto-Bailout), 30%, 70%, or 100% the ESC will use whatever power it has available to maintain the pre-programmed RPM regardless of battery voltage or prop load - up to 100%, of course. In the second .jpg below, you'll notice that the black line - throttle input - and the red line - RPM (2100) - stay constant while battery voltage drops thru the flight. The blue and green lines - ESC power input (foot on the gas pedal) and amperage - are jumping up and down in response to collective inputs.
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There are also options for using an external governor. Hobbywing makes a sensor for $4 that you connect to two of the three motor wires and it feeds the motor RPM back to the governor. The governor then tells the ESC how much juice to put to the motor. The Futaba governor in the CGY-750 (a helicopter flybarless gyro) can read an RPM channel from your transmitter off of the S-bus feed. You could conceivably set as many RPM's for it to follow as you have conditions in your radio. And you'd also get the side benefit of a three axis gyro that is fully controllable (all three axes 0% - 100% gain) from your transmitter as well.
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Just make sure you change the name of the "TechInspection" condition to something less obvious.
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