DIY Robinson Moth Trap

[Galeus]

Hi All,

I thought I would build a Robinson Trap in the next few months from scratch and would like to ask everyone if they had the chance to do this, what would they change/recommend/refine etc on their current trap - if anything of course?

I've sourced this base which is around 700mm wide and 400mm high to start off with..


The funnel is the bog standard 12" home brew funnel from the wonderfully named website BiggerJugs.co.uk although I was also thinking of a metal funnel from here Metal Funnels | Jerricans & Pumps | Drum & Gas Cylinder Storage | Hazardous Substance Control | Safetyshop


The throat diameter always seems to be a grey area to me ? You never seem to read much about what the optimum size is per funnel diameter do you ? I've settled on 140mm only because it's a natural size due to the ridge that holds a filter for brewing on this particular funnel ! It's obviously a compromise between being big enough for the moths to enter but not too large for them to escape easily !

I have the smallest lampholder (ES27) that I could find to alleviate unnecessary bulk at the throat.

For the baffles I thought I would use polycarbonate as that appears to be the strongest material of all the plastics available and is of course crystal clear - width of material 2mm perhaps ?

It seems obvious to me(?) to extend the usual height of the baffles to extend well above the bulb by at least, say, 6" to maximise moth deflection into the funnel ? The commercial baffles only seem to cover about half the length of the bulb inside the funnel for some reason ?

For the bulb I thought I would try the Paul Batty 125w Iwasaki, at least to start with - not cheap though !

I think I'll be OK on the ballast/capacitor etc

BTW anyone know why you get a higher UVA output with a cap fitted across the choke ?

I think that's it !

I should emphasize these are only MY thoughts so if anyone has any suggestion/recommendations/thoughts etc I would really appreciate hearing from you.

Until the next stage.....

Many Thanks in advance.

G

[Jim Ford]

Originally Posted by Galeus

BTW anyone know why you get a higher UVA output with a cap fitted across the choke ?

Maybe it's to do with Power Factor Correction (drawing on knowledge from <mumble, mumble> years ago!)

With an inductor (eg choke) in circuit, the voltage and current are out of phase. This means that whilst you may be drawing 1 amp from a 240 V supply, you won't be getting an output of 240 Watts at the lamp. (Which is why A.C. appliances with inductive loads are often rated as V.A. rather than Watts.)

Voltage 'leads' the current in an inductor, whereas current 'leads' the voltage in a capacitor. Putting a suitable value (and rated) capacitor in parallel with the inductor, corrects the phasing of the supply.

Jim