Voltage Booster (XL6009) with Digital Potentiometer

I bought a few of these voltage boosters, but I'm wondering if I can replace the trimpot with a digital potentiometer. Has anyone done something similar?

The voltage booster I bought is this: 2 PCS XL6009 DC-DC ADJUSTABLE STEP-UP POWER CONVERTER MODULE REPLACES LM2577 | eBay

And I'd de-solder and replace the trimpot with something like this: Digital Potentiometer - 10K - COM-10613 - SparkFun Electronics

I'm also not sure which digital pot would provide the same range of resistance as the trimpot.

Any help is appreciated.

Well now, there are a couple of problems here. :astonished:

The first is that the potentiometer you are replacing is connected directly across the output voltage of the XL6019. Now the digipot you cite, the MCP4131 is rated to an absolute maximum of 7 Volts, so this would not be useful for generating more than 6 V.

The second and more critical problem, is that the digipot will not be initialised until your code programs it, so until this happens the "boost" converter will be completely uncontrolled and will likely generate its maximum possible voltage - 36 V or more! :astonished:

And just to make it worse, if you connect the potentiometer to that module with any significant (more than a cm?) of wire, the regulator may become unstable in any case. :roll_eyes:

Yikes. Ok, I’ll scrap that idea. I may end up using two voltage boosters and alternate in between the two as needed in lieu of a digital pot.

The project is for a motorized dome door opener for an observatory (a new, and rather large, refracting telescope at the South Florida Science Center). The entire observatory has been overhauled and it fell on me to upgrade the dome door from hand operated to motorized and remote controlled. The motorized and remote-controlled part of the project has been fully completed. But I still need to solve the battery charging part of it.

To fully understand the project you’ll need to read what I posted about it on reddit (it’s a quick read): https://www.reddit.com/r/arduino/comments/fadh6a/arduinoenabled_observatory_dome_door_opener/?utm_source=share&utm_medium=web2x

However, I still need to be able to charge the batteries without getting up on a ladder every time and hooking up the charger to the two terminals. As I’m sure you would know a dome in an observatory is usually rotating while tracking stars, which eliminates the option of having the motor controller for the dome door permanently plugged in to an AC outlet (hence the need for a battery-operated system). Also, since time and money are a constraint, a copper or metal track installed on the perimeter of the dome that provides the necessary power to the motor controller (through a sliding contact) would be unfeasible and probably unreliable.

Two options come to mind:

  1. A small solar panel outside of the dome that charges the 12V batteries, or
  2. A Qi charger inside of the dome. The transmitting coil is stationary and the receiving coil would spin with the dome. When the dome is not being used, it is returned to it’s home position (where the two coils are side by side) and the batteries are charged.

I opted for the second option. The Qi charger I purchased is giving me 12V. I needed the voltage booster to get it up to 14V to charge the batteries, but I also need to reduce it to around 13.8V or 13.5V to give it a floating charge once the batteries are fully charged (this is where I was looking at the digital pot option). However, I can simply use two voltage boosters and switch in between them with a relay shield once the battery has reached a certain voltage (I bought a high-precision voltage sensor to tell me when this should be done).

I would have saved myself the headache by buying a charger off the shelf. But the problem is those chargers are AC to DC, and the Qi chargers obviously only provide DC. So, in summary I’m trying to build a battery management system that runs solely on the DC provided by the Qi charger. I think I’m almost there but I’m open to any other ideas on how to do this.

If you or anyone has a better idea I’d appreciate your thoughts and inputs.

I should have thought that simply choosing the "float" voltage would be just fine - the battery may just charge a trifle slower. Th "Qi" charger should be adjustable.

There would be ways of arranging spring-loaded contacts to mate when the dome is in its rest position.

If you want to make the output of a XL6019 based boost converter switchable by an Arduino between 14.0 volts and 13.5 volts, you could replace the potentiometer with resistor network like this, although I don't actually recommend it:

Voutput----/\/\/\/\-----X----/\/\/\/\-----X-----/\/\/\/\----ground (common)
             10K       FB       980R   Arduino     22R
                     (1.25v)            Pin

Arduino Pin state:

LOW = 14.0volts,
High Impedance (NOT high! i.e. as input pin) = 13.5 volts.

This, however, depends on the accuracy of the XL6019 internal 1.25 volt reference and the resistor network has to be kept well away from the inductor.

It appears you are charging a Lead Acid type of battery. Try this link: XL4015 5A DC Buck Step Down Power Converter Voltage Current & LED Voltmeter USB | eBay it is a XL4015 5A DC Buck Step Down Power Converter Voltage Current & LED Voltmeter USB. It will allow full charge by constant current then when full charge is reached it will go to a float voltage. I think that is what you are trying to do.

+1 for spring loaded contacts, that should be the easiest and possibly most reliable solution and should work fine as you return it to the exact same home position time and again. Then you can basically hook it up to a regular charger for your battery.

Or, as suggested on reddit as well, use some kind of a slip ring for power. You may be able to get away with just one (using the bearings for the return). Continuous rotation of your dome and continuous power to your door motor.

After reading some of the responses I think I'm going to buy some spring loaded contacts. I'll have to print a couple of 3D parts to hold the contacts. It's such an easy solution. The hassle of designing/printing a couple of 3D parts are more than made up for the fact that I wouldn't need to build a battery management system from scratch.