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3021 Buckpuck question

2K views 3 replies 4 participants last post by  wilso_ac 
#1 ·
I should probably post this over at CPF, but...

I have looked around and can't find any reference. When using the 3021 and leads longer than 18 inches from the battery it says to use a capacitor on the leads. The diagram shows two leads in as best as I can tell. Where do I put the capacitor as I can only see one positive lead in on mine or is the diagram talking about a capacitor across the positive and negative leads. Thanks for tolerating a LED newb.
 

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#2 ·
To be honest I wouldn’t worry about running one unless you find you’re having problems.

There was a thread here somewhere where we went into more detail, but I can’t seem to find it. It’s mainly used to help with electrical noise if the Buck Puck is being run from a noisy power source. It would be an advantage if you were running some sort of microcontroller to handle dimming, but even then it probably wouldn’t be an issue. ;)

And yes, the capacitor (around 220uf from memory) would be placed across the positive and negative leads on the input side.

Dave.
 
#3 ·
Hi Zen,

the capacitor should be placed across the VIN+(5v to 32v) and the VIN-(GND) pins of the buckpuck. The diagram shows a polarised capacitor such as an electrolytic, however, the datat sheet only states a 220uf 50V capacitor. A typical capacitor that you could use is shown here

Please note the indication of the negative pin of the capacitor. It is very important to get the polarity correct. I have no idea who to recommend as a supplier in the US, but Radio Shack could be a starting point.

Hope that helps :)
 
#4 ·
Hi Zen,

A capacitor is generally used in this application as a filter, AC goes through the capacitor and to ground instead of through the buckpuck/light cct, this protects the buckpuck from interference/crappy power supply - imagine static on a radio station. because we all run our lights from DC its probably not worth worrying about to much as DC will not go through a capacitor in this type of installation.

I run my triple cree from a battery pack in a water bottle mounted on the seat tube. No worries with any interference

As Low rider says its probably more important when running the buckpuck from a 'dirty' power supply such as a 240V to 12v downlight transformer, DC from batteries is generally pretty good.

Its not going to hurt putting one in there, if you do put it as close as you can to the buckpuck to ensure the effect is greatest.
 
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