TPL0501 Digital Potentiometer Controlling Higher Voltage Problem

Other Hardware General Electronics
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Pardon me if I posted this in the wrong categor as I'm not sure where to :smiley:
So my project or at least idea for now is a "DIY ReefLight Controller". I have one of these chinese "blackbox" led light it has a manual brightness control using a traditional 100K ohm pot. The goal is to have some sort of control and scheduling software/hardware system for the light. Example: 8:00AM 10% Blue Channel 5% White Channel, something like that.

So I checked the hardware of this light and it's pretty simple, just a led driver outputing 60-100vdc to the led array and 2 pin for control. This 2 pins outputs 13.3vdc and other one is GND. The way that the brightness is controlled is by adjusting the resistance between these two pins. The manual pot wiper pin is connected to the 13.3v and the GND pin is at the LOW pin of the manual pot. The lower the resistance in between these 2 pins, the dimmer the leds are and vice versa. If you short them leds will turn off. Pretty simple so far. :grin:

My idea is to replace that manual pot with a digital potentiometer which I can hook up to my ESP32 and control the light from there. I have no issues regarding the software side, I can set the wiper step and such.

Now, going to my problem; the digipot I have is called TPL0501 a 100k digipot with 256 taps. Great digipot for fine tuning the brightness of the leds.

But here's the catch: this digipot can only handle 5v max on its control pins. Searched the forum for hours to see if anyone had the same problems with mine but to no avail. Also I tried other approach like sending PWM signals or Analog 0-10v signals but the leds flickers so much and this is the closest solution I have so far.

I tried the voltage divider theory but that affects the minimum resistance I need. The resistance should range from (minimum 6.3 ohms and maximum 94k ohms) for the leds to dim and have max brightness properly. Please see the attached schematic as well the image of the LED driver and LED itself if that can help. Thank you very much Arduino Team!

LED Driver:

download
download450×450 74.8 KB

LED Light Itself:

download (1)
download (1)450×450 197 KB

Basic Schematic of what I have done so far:

Schematic_TPL0501
Schematic_TPL0501572×438 12.8 KB

2

There are digital potentiometers that will work at higher voltages.

Such as the DS3502:

Here's the DS3502 datasheet.
Can be used at up to 15.5V.

1 Like
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I'm located in the Philippines and have a very limited online shopping platform options. What I need is 100k though. So I can only use this TPL0501 or the most common X9C104; both operates at 5v max on their control pins.

4

Sorry, I hadn't checked the resistance value.

5

Since it is easy to see please post an annotated schematic.

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The schematic is at end of the post. The schematic of the LEDs don't matter in this project, just that "2 Control Pins" or logic of the LED dimming.

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You are describing a constant current led driver. To properly dim you need to adjust its output. Without more information I cannot give you much more help.

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The specific power supply (the one I posted) doesn't have any datasheet available online. The chinese company Wattshine, only makes it upon request. But what is obvious upon visual inspection is that the control is only dependent on these 2 pins (where the manual pot is previously connected)

This is the part I don't get. I don't have much knowledge in electronics. Can you enlighten me on this?

Thanks so much for your time.

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Okay so after few weeks of testing, I was able to complete the project. Just simply connect the pins of the digipot to the LED control pins :smiley: It turns out that these two pins don't give out current or voltage. It's just a variable reference for the power supply to "know" how many voltage will it give to the leds (60-100vdc). So connecting directly without using logic level shifter/op amp or etc., is safe.

Maybe this will help someone modifying a Chinese Blackbox ReefLight (Wattshine) in the future :smiley:

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