Potentiometer 'bulk'

I’m looking at part RJS500E-ND and similar products.
Which is a 500ohm pot that can handle 50W.

It says ‘bulk’ next to the price. So there must be a few of them? Or are they really like a hundred bucks each?

Welcome to the forum.

No, the “Bulk” is vs “Tray” which is the packing method regardless of quantity ordered.

Potentiometers with a 50W power rating are extremely expensive devices. This is why they were replaced in nearly all products with other electronic circuits 40+ years ago making them even more expensive nowadays.

On top of that they work by converting electrical power to heat which is a big waste of electricity, and you may need to use even more electricity to remove all the extra heat they generate.



On a side note, could you advise towards figuring out a solution that doesn’t involve expensive potentiometers…

I am trying to run two LED channels off a single constant current LED driver, with a mechanism to blend between the cool white and warm white channels.

A 1K pot worked for about a minute but then melted.

The lower resistance ideas I’ve considered are, PWM, and transistors in some feedback loop, but not being an electrical engineer, the details are puzzling.

Would you recommend looking further into one of these approaches?

Hi @djb, it depends partially on the type of driver you have. Many drivers these days have wiring options for dimming built in and are designed with either a PWM or analog dimming circuit in mind. If you have the part number for that driver, it may be worth checking the datasheet to see if there’s a feature you can take advantage of instead of building your own dimming circuit from scratch.

We do also have some external dimmers available, though again you would want to double check the options against your driver to verify that they are compatible:

Trying to divide a single constant-current source into two separate streams is not trivial.

Depending on the particulars of your LEDs, you might want to take a look at the dual channel Bridgelux Vesta Flex series of LED drivers, control modules, and programmer which are designed for such applications.

Alternatively, you might find it simpler to just use separate drivers for warm and cool LEDs. To accomplish this, you can either use independent AC-DC constant current drivers or a single AC-DC converter and a pair of DC-DC constant current devices from there.