Gemfan LED Props – Moonlight Propellers

by Oscar

Putting LED in propellers was unimaginable because propellers on FPV drones spin hundreds of times per second. Well, Gemfan did it and it looks awesome at night. Introducing the Gemfan Moonlight props with integrated LED.

Some of the images in this post were taken by Manfred Maximilian Götzl. Many thanks to him!

Where to Buy

At the moment, only 5.1″ size is available (51466). All new batches are now V2 by the way.

The Gemfan Moonlight props require battery, which has to be purchased separately. Recommended batteries are: LR521, LR69, AG0, 379, or SR521.

You can use two SR521SW button cells for each prop: https://amzn.to/3tNlnrB (affiliate link)

Construction and Assembly

From the outside, The Gemfan Moonlight prop looks just like a normal prop. But if you look closer, there is empty space in the hub, where you can put the LED, electronic circuit and batteries.

There is only one LED per propeller, and it’s built on a piece of flexible PCB that you can slide into the hub of the propeller.

The LED should be placed to face toward the blade with embedded color markers. These markers can deflect light from the LED. And that’s how they creates this effect that the light seems to come out of the blade.

Why just one blade? Not all three? Well, you probably can’t tell the difference any when it’s spinning 500 times per second :) So having just one LED makes the construction simpler and lighter.

I have to say, this is genius! Kudos to Gemfan for this clever solution.

Including batteries, these LED propellers weigh about 4.6g each, almost a whole gram heavier than normal props. That means they are slightly less responsive, but who cares as long as it looks pretty at night? :)

There are different color options too.

Power

The LED requires two SR521SW button cells (for each propeller), or you can also use LR521, LR69, AG0, and 379. With SR521SW, it should provide 30 mins of power continuously.

There is an on/off push button on the flexible PCB, and when you squeeze the hub, the button is pressed and the LED lights up. So when you want to enable the LED, just tighten up the prop nuts, and when you don’t want it to light up, just loosen the nuts.

Changing Props and Costs

You shouldn’t have to worry about damaging the prop, because you can just transfer the circuit over to a new prop. Theoretically, the cost of using these LED props should be similar to using normal props.

However, I haven’t found a link where you can buy just the replacement props yet. All the listings currently (Feb 2021) include the LED circuit and so it’s quite expensive to replace.

Although the Gemfan Moonlight is such an elegant solution to LED props, having to change battery every 30 mins can be annoying. And those little batteries aren’t exactly cheap, the cost of using LED props can add up quickly. Not to mention the added weight is not great for performance.

So I think they would be nice for special occasions and racing events, but they won’t be my daily props.

The next step would be some sort of wirelessly powered LED props :) Not only cheaper but lighter too :) Okay I am dreaming.

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3 comments

Arthur 14th February 2021 - 3:41 pm

It would be really cool if they used the spinning motor magnets as a sort of dynamo thing so that they produced electricity as the motors span.
You wouldn’t even need a battery!

Reply
Bernard Mamo 11th February 2021 - 10:28 pm

“The next step would be some sort of wirelessly powered LED props :) Not only cheaper but lighter too :) Okay I am dreaming.”

No you’re not. IF you follow fleming’s left hand rule you could work with the rotation of the props, a magnet, and a very small coil. Somehow i can picture it in my head but I cannot put it in words.

Reply
Jim 10th February 2021 - 10:23 pm

I wonder if you could have a LED in the motor housing and then simply some sort of reflective material on / in the prop that would make it ‘glow’ like these do?

Reply