Making a timed UV light

Projects General Guidance
1

Hi,
I'm looking to make a curing station for my 3D printer. I went and got an led curing light for gel nails from a beauty supply store and tested it out on some of my 3D resin, and the UV leds seem to work well with it. The only issue is, rather than an on/off switch, the light is on a 45 second timer. This is ok for the time being, but I'd like to upgrade it and was wondering if I could do so with an Arduino.

I have no experience with Arduino, but have some familiarity with programming/coding and soldering. Would it be easier to "bypass" the internal timer of the light, or dismantle the parts to make a light with a variable timer?

I looked up the writing on the circuit board but got no additional information to what I found on the package. I'm guessing without a lot of equipment and know-how, that I should probably just remove the leds and start from scratch.

Ideally I'd like to be able to enter in the number of hours and/or minutes into the timer, and hit start; turning on the light until the countdown ends. But I am open to using a timer that only uses minutes as a unit if that is simpler.

How reasonable a project is this for a beginner and what would be the best way to move forward?

Here are some pics I took of the nail cure light parts, if that helps. The box says it has a power of 4W and ratings of 100-240 VAC, 50/60 Hz, 6W

Thanks for any help you can provide.

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2

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We need a clean closeup view of the Q1 circuit area.

Looks like all the LEDs are driven by Q1.

You might be able to add a base/gate resistor to Q1 and drive the transistor from the Arduino.

Could also toggle the on board switch every 50 seconds or so with the Arduino.

What does the power supply say about the output voltage?

Do you have a soldering iron, solder, small wire cutters, 24AWG wire?

Will you be needing to keep the manual way of operation?

3

So many LEDs in parallel! :astonished:

Mike (GM) will be apoplectic! :roll_eyes:

4

Q1 is the switch transistor - the pushbutton bypasses it to start and the 4060 timer holds it on for the desired period.

5

larryd:
We need a clean closeup view of the Q1 circuit area.

Looks like all the LEDs are driven by Q1.

Here's a close up of it, apparently my phone's macro stinks, had to sneak a shot from my work's camera. (Don't tell!)

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larryd:
You might be able to add a base/gate resistor to Q1 and drive the transistor from the Arduino.

Could also toggle the on board switch every 50 seconds or so with the Arduino.

What does the power supply say about the output voltage?

It's just a micro usb cord.

larryd:
Do you have a soldering iron, solder, small wire cutters, 24AWG wire?

Everything but the wire, easy enough to get.

larryd:
Will you be needing to keep the manual way of operation?

Nope, not if I can set my own time in minutes or greater.

6

It's just a micro usb cord.

Does this then go to a 5volt power supply?

If the power supply is 5V, this setup should work.

However, you will need to test the circuit before you commit to it.

Toggle the Arduino output 1-2 seconds after the on board circuit times out.

If things normally time out at 47 seconds then toggle the Arduino output every 49 seconds, keep doing this for your 1-2 hours then stop.

If the board circuit allows you to reset timing by pushing the button at 40 seconds (you can test this out now) then toggle the O/P every ~40 seconds.

Probably best to confirm the 100 and 120 series resistors do not get too hot.

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7

Could be that the button is connected to 5volt (not ground), and a p-channel fet is used high-side.
"100" and "120" is 10 and 12 ohm (a 10 or 12 with zero zeroes).
The whole board could draw about 500-650mA (1.5-2watt of LED).
Leo..

8

Looks like pin 11 of the on board controller is VSS, would make the switch going to GND.

R8 would be a pull-up, C1 a de-bounce cap.
Edit: Actually C1 looks like it is for decoupling.

Diodes + are marked as shown on the component side.

9

Agreed. Didn't see the + next to the diodes.
Leo..

10

larryd:

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For some reason I'm having a hard time telling the color of the first two bands, is that a 220 or 330 resistor?

11

220 Ω

12

larryd:
Looks like pin 11 of the on board controller is VSS, would make the switch going to GND.

That is extremely strange, since the board "pour" seems to connect to the casing on the USB connector- which is of course, ground. :astonished:

13

Funny thing was that it took me longer to find the wire than I thought.
I see a lot of different scripts on the forum for specific lighting setups. What would be a good basic one to test this?

14

See:

LED_BUILTIN is pin D13

15

I like the idea of disconnecting Q1 from U1 pin and driving it with an Arduino. Digital pin to gate and ground connection. Can’t see if it’s highside switching from the pictures on a phone.

16

Looks like the LED board designer left lots of copper for heat sinking.

Paul