submitted 1 year ago by MissJinx@lemmy.world to c/askelectronics@discuss.tchncs.de

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?

top 7 comments

sorted by: hot top controversial new old

[-] SomeoneSomewhere@lemmy.nz 3 points 1 year ago* (last edited 1 year ago)

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@lemmy.world 1 points 1 year ago

Its a 5mm Led This is the tech info

[-] SomeoneSomewhere@lemmy.nz 2 points 1 year ago

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

[-] MissJinx@lemmy.world 1 points 1 year ago

Thank you ao much! I'll Try!

[-] nothacking@discuss.tchncs.de 3 points 1 year ago

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@lemmy.world 1 points 1 year ago

Its a 5mm Led

This is the tech info

Do you think 6 AA batteries would hold?

[-] Hagdos@lemmy.world 2 points 1 year 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.

this post was submitted on 03 Oct 2023

8 points (100.0% liked)

Ask Electronics

3173 readers

1 users here now

For questions about component-level electronic circuits, tools and equipment.

Rules

1: Be nice.

2: Be on-topic (eg: Electronic, not electrical).

3: No commercial stuff, buying, selling or valuations.

4: Be safe.

founded 1 year ago

MODERATORS

DavideAndrea@discuss.tchncs.de

linker3000@discuss.tchncs.de