Need EE input on design

Hi,

Am currently trying to design a 2-channel LED Driver to include analog and PWM dimming. I am using the RDC-24-.70 LED Driver. I have completed what seems to be the correct way to do the analog circuit but unsure of it as well as how to use the pwm with it also. Any help would be appreciated.

untitled.pdf (9.38 KB)

Project1.jpg

The PWM input is active-low. If you connect it to a PWM pin of the Arduino you should get maximum brightness at analogWrite(0) and minimum brightness at analogWrite(255).

The datasheet shows lots of example circuits: http://www.recom-international.com/pdf/Lightline/RCD-24.pdf

Am kinda lost when i'm looking at the examples on the data sheet. I notice it uses the analog dimming pin also for the PWM signal and not the PWM On/Off pin. So i'm very lost when it comes to trying to dim the driver by a pot and using the PWM signal also. Thanks for your help.

Martin

Have you already purchased the dimmers? If so, which option did you get? "/W/X3"? That seems to be the only variant that can do both analog and PWM dimming. You feed 0-4.5V into the analog dimmer wire to set the maximum brightness and hook the PWM wire to a a PWM output on the Arduino to fade from off to whatever brightness is set by the analog input.

The data sheet seems to be saying that the analog input adjusts the current output. That probably means that the light output will not change linearly with the analog dimmer input.

Perhaps you should get the '/W/X2" mode with PWM-Only. Then use an analog input on the Arduino to modify the PWM output to provide a "dimmer knob" effect.

What is it you wanted to accomplish with having both analog and PWM dimming?

I was actually looking at getting the RCD-24-x3 for PCB application for running 3W LEDs in an aquarium hood i'm currently designing with a business partner. Currently we are using 4x CAT4101 Drivers with analog dimming via pots on the front of the unit as well as using the Uno for a small lighting program to ramp the driver up and down for sunrise/sunset effect. Reason i'd like to try the RCD-24-x3 is it will drive 10Leds instead of the 6 with the CAT4101. We would rather go with running 2 of the RCD-24-x3's to keep costs down and be able to provide a cheaper alternative to the $500+ LED systems available.

What are you using for a power source? If you don’t need the wide input voltage range of the RCD-24 series you can save a good deal of money by using a simple constant-current power supply and do all the dimming in software:

A MOSFET can be used to PWM the LED’s (turn them on and off).