Newbie BuckPuck question

Hi,

Might be a dumb question but is it ok to have the on/off switch between the Buckpuck and LED rather than the more normal position between the batteries and Buckpuck?

The tech sheet mentions "Output open circuit protection" but I want to make sure before trashing one!

Alex

Ill risk advising another Newbie

I would not do it
The fact that there is protection required for what you are trying to do suggests that you should not be doing it.

The circuit will be powered up and would never be "off" which can only drain the batteries.
There may also be a time limit on the short circuit protection works before over heating.

Nick

Definitely no.

The buckpuck is a current regulator. That means it adjusts its output voltage until the desired current is flowing. If you switch out the load with the regulator still powered up, then it's voltage will shoot up to it's maximum output voltage. There is an output capacitor that will get charged up. Next time you switch on the LEDs, they will get hit with a huge surge of current as the charged capacitor dumps into the LEDs. Once the output cap discharges, only then will the regulator circuit begin to properly regulate the current going to the LEDs. The surge current when you flip that switch would likely damage or destroy your LEDs.

"Output open circuit protection" only means that the regulator will not exceed a certian voltage when the load is disconnected - this is a self-protection mechanism, designed so that the output cap does not get charged to extremely high voltages, possibly destroying the cap and/or other parts of the regulator. That protection is designed to protect the regulator its self from your mistakes, it will not really protect anything you attach to the regulator.

So no, don't switch the load, switch the power to the regulator.

Thanks for the info guys, as I had an old light kicking about with a LuxIII and a 1A Buckpuck I thought I would break out the soldering iron and give it a go anyway....

Well it seems to be working fine, no blown Luxeon, no hot Buckpuck or cells.....maybe its only a matter of time! I'll take the cells out before going to bed tonight!

I won't use this on the "production" lights and instead run a 4-core power cable; 2 for the +ve and GND to the LED and the other two as the out and return to the switch in the casing so its effectivly between the power and driver....now I need some 6mm OD 4-core cable, Maplin here we come (again!)

Alex