Main Site Documentation

Control a 20V Led


#1

Hi,

I’m starting playing with gadgeteer modules, and I have several LEDs of 20v ( 1A ) that I want to dim ( using PWM ).
What kind of gadgeteer module should I use to manage this ?

Thanks in advance.


#2

That’s pretty high voltage for most modules. The Load module might help. You’ll need to see if it can switch fast enough for your needs.

http://www.ghielectronics.com/catalog/product/364


#3

Treat it like AC. Give it a separate power source and tie an optocoupler to the PWM to control it.


#4

I concur.

The BCP55s on the Load module should be able to handle the switching fine. Just use a low frequency when you’re PWMing – it doesn’t need to be more than 200 Hz.

I’d recommend ignoring @ Skewworks advice about using optocouplers. Most optocouplers aren’t designed to directly drive loads like that, and, as @ ianlee74 already noted, there’s a perfectly good off-the-shelf solution (the Load module) that will work perfectly for your application.

The bigger issue is the constant-current-source power supply that you’ll need to power the LEDs. Even if they’re labeled “20V”, you can’t drive them directly with a voltage source; you’ll need a current source to drive them, as LEDs are rated for a specific amount of current.


#5

I just wanted to note here that the Load module page says “The 3A 50V transistors…”

According to the schematic the part#'s listed there are actually 1.5A, 60v

So either the devices page text is in error, or the schematic part# list there are wrong.


#6

@ VersaModule - The schematic part# is wrong. The right part# is PBSS4350Z, which is a 3A 50V transistor. We will be correcting the schematic. Thank you for pointing this out.