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30 UV led circuit (self.askelectronics)

submitted 9 months ago by MissJinx to c/[email protected]

7 comments fedilink hide all child comments

Hello! I bought 30 simple UV leds (those with a big and a small leg, not a single strip). I'm trying to build a UV station to dry my resin but idk how to proceed. I tryed watching some videos but there is a lot of math to build that and I can't do it. I have 30 led lights, 5 resistors of 100 and 5 of 300. I wanted to use AA batteries. Do I need 8 of them?? Its not going to be turned on for long, just some 30 seconds at a time.

Can someone help me?

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[–] [email protected] 3 points 9 months ago (1 children)

You could connect the LEDs in 5 strings of 6 parallel LEDs, each string with it's own 100 ohm resistor. You will need a significant amount of voltage for that, at lest 7x the threshold voltage of the LEDs

[–] MissJinx 1 points 9 months ago (1 children)

Its a 5mm Led

This is the tech info

Do you think 6 AA batteries would hold?

[–] Hagdos 2 points 8 months ago

AA batteries can supply plenty current, the question is for how long.

You need about 1.3 Watt for 30 LEDs (I'm assuming 15 mA, 3V). A rechargable AA battery has about 2.4 Wh according to Wikipedia, so 6 AA batteries will last you 2.4Wh * 6 / 1.3W = 11 hours.

I have no idea how curing works, but 1.3 Watt feels very low. That amount of power is fine for visual lighting, or for signals (turn on a TV), but energy wise it's very little.

[–] [email protected] 3 points 9 months ago* (last edited 9 months ago) (1 children)

Do you have a datasheet/part number for the LEDs, or at least a picture and diameter?

Because battery voltage reduces over time, the LEDs will get dimmer as the battery drains fairly quickly. If possible, running it off a mains plugpack (e.g.12V like for a router or external hard drive) would be good.

An example UV LED has a forward voltage of nominally 3.7V. Two in series on a 12 (8x1.5V) supply gives us 12V-(2x3.7V) =4.6V to drop across the resistor. We want ~15mA, so need a very roughly (V/I =R) 4.6V/0.015A=300 ohm resistor.

When the battery is nearly discharged, at 1.1V/cell it will be 8.8V, giving 1.4V across the resistor and V/R=I 1.4V/300ohm= 4.7mA.

So you would connect each pair of LEDs as:

BAT+ RES +LED- +LED- -BAT all in series. Like this.

You'll need another 10 300 ohm resistors for 15 total, one per pair of LEDs.

[–] MissJinx 1 points 9 months ago (1 children)

Its a 5mm Led This is the tech info

[–] [email protected] 2 points 9 months ago (1 children)

Three in series per 300 ohm resistor would be OK with those.

[–] MissJinx 1 points 9 months ago

Thank you ao much! I'll Try!