Fade 12v load using arduino over 1 minute

I'm relatively new to arduino and have been reading on the forums all day for some guidance but can't seem to find one that resolves my particular problem.

I am looking to fade a 12 volt load programatically. My set up includes an arduino nano, a 12 volt power supply, and a 12 volt, 0.4watt/sqft variable tint screen. The screen basically can be controlled by a continuous voltage supply (not many amps are needed to power the screen). At 0 volts, the screen is opaque, and at 12 volts the screen becomes clear. My goal is to vary this tint over time and watch it get increasingly more and more clear from the original opaque state.

The screen needs a constant voltage supply so I do not think using PWM and a transistor will work for my needs (however I could be wrong).

I know that increasing the resistance between the load and the 12 vdc power supply will decrease the voltage and solve my use case. However I am struggling to find a device that can programatically change the resistance through the arduino. An analog potentiometer could work, but the problem with this is that you have to physically spin the knob in order to change the resistance. Digital potentiometers also typically only work between 0-5v (my application is 0-12v).

Any help/guidance to help solve this problem would be amazing! I am just looking for the best device to programatically vary voltage between 0-12 vdc using the arduino interface. Thank you in advance!

Please post a link to the datasheet or product page for the screen.

https://www.amazon.com/HOHO-Electronic-Switchable-Projection-21cmx29-7cm/dp/B079K9BG84

The data sheet is the 6th picture down.

I see nothing related to a data sheet on that page, and have no idea what you mean by "the 6th picture down".

There is not enough information in your post to answer the question. However, it is certainly possible to build or buy an electronically controlled 0-12V linear power supply.

What kind of information do you need, I will look for more information online. I bought it on amazon and the 6th amazon picture is of the specs of the screen. I’ll attach the picture that I am referring to.

That little table doesn't show up on my screen, and I still don't know what you mean by "6th picture".

The table screenshot you posted suggests that the voltages required are AC, 60-75V at 50 Hz.

I'm out. Good luck with the project!

Ok, well thank you! And yes it can run off of 60-75VAC but also works from 0-12vdc (I successfully got it to fade using a variable switching power supply (https://www.amazon.com/TekPower-TP12001X-Variable-Switching-Digital/dp/B00PX90PIU). The range of use for the screen with this power supply is 0-12 VDC.

If the thing works like any LCD display, using DC voltages will work for a little while, but eventually destroy it.

Also, on the picture of the data sheet that I just posted, the input voltages go as follows : 220 VAC, 110VAC, 24DC, 12DC. It is tough to see that because they placed a watermark right over this information, however that is what it lists as recommended inputs. My goal is to use the 12 VDC input.

Is there any electrical device that you would recommend to vary this 12 VDC from 0-12V using the arduino?

Again thanks for your help on this!

it is certainly possible to build or buy an electronically controlled 0-12V linear power supply.

Yes, I have been searching for different power supplies but I cannot seem to find one that is compatible with arduino and is in this range of voltage. Do you know of any/have any links to ones that people have deployed? If you have a link to an example that would be super helpful! Thanks!

My first instinct would be to try using an LM317 to build an adjustable voltage regulator circuit. Keep in mind that it won't go below ~1.25V, not sure it would be a problem for your application, you have to try.

I'll let you look up specs for the LM317, not sure how it would react dropping your input voltage to 1.25V for long periods of time, it might get toasty.

Then, you might be able to replace R1 and / or R2 with a digitally controlled potentiometer like the MCP413X series from Microchip.

melkalehun:
Then, you might be able to replace R1 and / or R2 with a digitally controlled potentiometer like the MCP413X series from Microchip.

That might not be a good idea since the MCP413X has a working voltage of up to 5.5 V and an absolute maximum of 7 V.

It is a common misunderstanding that “digital potentiometers” are in some way, a digital version of a conventional potentiometer. They are in fact, digital volume controls for use in audio equipment which allows software or remote control. That is their purpose. And another consideration is how they behave during boot-up of your system, so using them to control a power supply would be fraught with danger.

jremington:
I see nothing related to a data sheet on that page, and have no idea what you mean by “the 6th picture down”.

There is not enough information in your post to answer the question. However, it is certainly possible to build or buy an electronically controlled 0-12V linear power supply.

6th thumbnail to the left of the product image.

Thanks for the responses!

I also noticed that a digital potentiometer has a safe range of 0-5v but that is the type of response I need from the device. Is there any other sort of device that can be used like a digital potentiometer but for this application?

I read up that you can use DAC like a digital potentiometer, and it can be used up to 15v? Is this correct or am I misinformed on this?

I've been searching for higher voltage digital potentiometers and found this http://www.farnell.com/datasheets/686036.pdf. Could this potentially work?

Is it possible to use a MOSFET to switch the 12 volt power supply on an off using the arduino's PWM, and then use a simple RC filter to smooth the PWM response that the 12 volt power supply would be receiving (by turning it on an off a bunch of times) to get the average?

Again, any guidance on this would be great. I am relatively new to all of this stuff and would hate to blow anything up by doing something stupid :slight_smile: