Hi -- I want to modify a small light cube that works with 24v DC PWM. I am new to electronics & arduino.
The cube contains a bunch of led's and has a rheostat that alters the brightness of the LED's by altering the PWM at 24v. My analog volt meter bounces at a very low (brightness) level, so I assume it's a PWM -- my digital volt meter always shows 24v...
I can see the power supply separate from the rest of the circuit, as well as the power to the LEDs; so I can insert myself between the supply & LED's
I want to use arduino to adjust brightness based on movement in the room.
What is best way to control 24v PWM from arduino, using a mosfet or ssr? will those be fast enough?
If I wanted to read what the PWM is at dim or high -- using voltage divider & opto-isolator? (again, which one would be fast enough?)
I can pull a solid 24v off the existing circuit, so I have a good power source, and can cut the current dimmer out so I can insert mine...
unfortunately I do not have a schematic of existing circuits....
I know I should buy an oscilloscope to see into the actual PWM, but just for 1 project it seems overkill; hoping I can do it with arduino...
Hi, can you clarify what you mean by "led cube"? Around here that usually means a 3D cube of 3x3x3 or 4x4x4 perhaps even 8x8x8 leds that flash patterns and animations. Is your cube simply a decorative room light in the shape of a cube? A picture would have been helpful!
I can't imagine how a 3D cube could run on a 24V pwm supply, so I'll assume the latter. What you might be able to do is replace just the pot with the Arduino. Can you measure the range of voltages coming from the pot?
It's a decorative box with several "depths" of diffused RGB LED's with a mirror in the center...
It's 24v that is coming off the board to the led's
Replacing the pot is exactly what I want to do -- but do I just use a mosfet? I want to avoid too much 'trail and error' in guessing the frequency that the PWM is at, so I want to know that value. I can use a for loop to try to guestimate the right pwm ....
Replacing the pot is exactly what I want to do -- but do I just use a mosfet?
It very much depends on what the pots are doing. It is unlikely that they are just directly limiting the current as that would be too much power for the pot.
in guessing the frequency that the PWM is at,
With PWM frequency is largely irrelevant it is the duty cycle that matters.