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Anomala albopilosa attraction by purple LED

The park near my house planted the lawn.
Since it was neglected without repairing, the caterpillar bred at the root.
The imago of the caterpillar which bred is Anomala albopilosa.
The large herd of Anomala albopilosa flies to my yard, and eats away a garden tree.
Then, I decided to make an attraction capture machine.
Although made based on the knowledge of a faint memory using blue LED, it was completely ineffective.
I have to make, after thinking seriously after all.

Considering & make

It read and hunted for the paper about insect spectral luminous efficacy.
Seemingly, many of insects have spectral luminous efficacy in ultraviolet rays strongly.
It seems that however, a wavelength with strong spectral luminous efficacy and the strong wavelength of attraction are not same.
And I acquired information that 400nm cause attraction is high to Anomala albopilosa gracilis.
I expected that the same effect as this was acquired.
Since optical power occurs having tried on 0.25W, I will make from the same conditions.
I select 400nm LED of Vf=3.2...3.4V, If=20mA, Angle=30degree, Max120mcd (100...120), because it is rather cheap.
First, unit conversion is carried out from mcd to W.
The lumen, unit of brightness, come from the spectral luminous efficacy of human.
The spectral luminous efficacy of human at 400 nm is 41.4 (lm/W).
If the angle-of-radiation characteristic of LED is assumed to be Lmabertain,
The total luminous flux F [lm] is F = (m + 1)/2π*I0.
The m is a half angle φ1/2 = arccos(0.5)1/m ,and I0 is a front luminous intensity.
My LED isφ1/2 =15 degree, then m=log (cos(φ1/2))/log(0.5)=log (cos(15 degree))/log(0.5)=0.05, then F=1.649*I0[lm].
At I0=120mcd, F = 1.649*0.12=0.198 [lm], then optical power = 0.198/41.4=4.7mW.
It mean than it need 250/4.7=53 pcs.
By weather-beaten, since the high voltage is dreadful, it is considered as 18V power supply.
Probably it needs 4V or more to current be constant, and then 4 series are limits.
( Since 30 mA is unlikely to increase even if Vf changes 0.1V at 40 degree Celsius, 4V will be enough for 4 series of LED. )
Then I decide 12 parallel, 4 series and 48 pcs in total.
When 12 parallel is used, considering cost, a space, and a time-and-effort target, a constant current circuit is
reasonable by using resistance only.
R=V/I=4/0.02=200 Ohms
Then resistance value is selected about 180...220 Ohms.
If 20mA, P=0.02*0.02*220=0.088[W] (=1/11), then 1/8[W] or more could be used.
And I select 15V/0.7A power supply unit, and adjust the output to higher.
Some plastic is also penetrated if it is 400 nm, though I useφ27mm glass test tube that I have.
Twelve phi6mm holes are made in 9 mm and a 1-mm-thick aluminum L angle every 8 mm, and twist L angle 90 degree.
Set LED to each hale and it fixed with the hot bond.
It covered with the rubber cover for table legs, and wound aluminum foil around the cover
for the prevention from ultraviolet ray degradation by solar in day time.

Result

It can attracted Anomala albopilosa very well.
Though this DIY is not well.
Because I made it too compact, the hot bond melt by temperature rise and the circuit is shorted in some days.
It has decreased to the following year to the extent that it says, "What was that outbreak?"
And then I never made again.

　 　

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