Converting a SMD LED (e.g. Samsung LM301H) into a through-hole 5mm LED? - Page 1
Forum section: electronics / projects

author: victorhooi
author_rank: Regular Contributor
timestamp: April 04, 2025, 09:55:41 am
content: I am looking at doing some experiments using the Pioreactor.https://pioreactor.com/It's basically a small-scale homebioreactor, based around a Raspberry Pi.The Pioreactor has a spot for you to add your own LED, so you can for example do photosynthetic experiments:https://docs.pioreactor.com/user-guide/using-leds#adding-leds-to-your-pioreactorHowever, it's expecting a 5mm through-hole LED:There's also a circular cutout in the black vial holder, which you poke the 5mm LED into (circled in red):If I wanted to use something like the Samsung LM301H (one of the most common horticultural LEDs) - AFAIK, it's only available in a SMD package.Sorry if this is a naive question - but is there any way to "convert" a SMD LED package to a 5mm through-hole style LED, with header pins?(I haven't really done SMD soldering before - so that might be an issue - and from what I've read, SMD soldering for LED modules is quite tricky -https://www.thcfarmer.com/threads/homemade-led-design-pcb-doubts.124642/).I did see that cutter.com.au offers LED modules on a "star" PCB:https://www.cutter.com.au/product/samsung-lh231b-5000k/Apparently the PCB usually has a metal core, for better heat dissipation (source).Any suggestions or ideas here? Or how would you approach this?

author: ajb
author_rank: Super Contributor
timestamp: April 04, 2025, 09:44:21 pm
content: Those LED star PCBs are meant for high power devices, typically in the 1-3W territory. That Samsung part is listed at 0.2W, and a typical 5mm LED will max out at tens of milliwatts. If you only want the LM301H for its spectral output, you could drive it at similar power levels to a 5mm LED and not need to worry about heat dissipation, so no need to worry about heatsinking.You could make an SMT LED work here by just soldering some relatively stiff wires to it (leads clipped off of a PTH LED or other component would be a good choice) or header pins, and then reinforce the solder joint with epoxy or superglue or whatever. With the LM301H, you might bend a little 'L' onto the leads before soldering, so they lay across the pads on the back of the LED.One other wrinkle here is the optical output pattern. With a typical 5mm LED, the clear encapsulant also serves as a lens, providing a fairly narrow output of 10-20°. Most SMT LEDs, including the LM301H, do not have such a lens and therefore emit over a wider angle, often about 120°. I don't know if that matters for this application, but it's worth knowing that the difference exists. There are SMT LEDs with integrated lenses, but they're less common, especially among the higher power parts designed for illumination.All that said, what is it that makes the LM301H so special or interesting for this application? The spectral output looks a lot like any white LED, maybe with a bit more power in the red/IR. Maybe it has better efficacy for photosynthesis, which matters a lot when you have operations needing many kilowatts worth of illumination, but that wouldn't seem to matter for a small experimental setup like this -- and the wide emission angle may negate that benefit anyway.