Portable battery solution for a 20 LED design - Page 1
Forum section: electronics / projects

author: justageek
author_rank: Newbie
timestamp: August 15, 2020, 09:21:19 am
content: Hi am new here..I happen to come across a germicidal UV disinfectant lamp circuithttps://www.gadgetronicx.com/uv-disinfectant-lamp-powered-solar-power/. It is said that it uses UV-C LEDs, that has a forward voltage drop of 5.2v and 50mA. That's quite high for an LED. I have been thinking to make this but with 20 LED's since 5 LEDs as shown in the circuit is quite less. Also the circuit need to be really portable and weigh less.If am going to use 20 LEDs that's four times more than what's shown in the circuit. Even if am going to use two pair of LEDs in 10 branches in parallel configuration that still needs a 12V supply and at least 500mAH battery. When I search for 12v batteries all I could find is batteries that are bulkier and will not fit for portable use. Any design advice to tackle this will be much helpful.

author: Whales
author_rank: Super Contributor
timestamp: August 15, 2020, 10:18:38 am
content: Quote2S10P is the common terminology for this. 2 series 10 parallel.QuoteFor a resistor-limited LED drive: approx 12 would indeed be a good starting point.Beware 500mAhvs 500mA, they are very different things.QuoteIf you search for "12V batteries" you will mostly find lead-acid batteries, which are indeed very bulky.Lithium-ion batteries are more likely to be something attractive to you. Have a read up on them, there are lots of topics around their safety in particular. Li-ion 18650 cells are easily found by breaking apart old laptop batteries and chargers are available online. Sidenote: it's worth measuring your charger to ensure it doesn't over-charge your batteries, don't trust anything.You can run 5.2V or 10.4V (or even higher V) LED strings off lower voltages if you want to. Either "boost converters" or dedicated "boost LED drivers" are useful things to research. These do however require more parts than the circuit you link to; but you can also get pre-made adjustable units for a few dollars.Finally: be wary of the severe hazards of UV-C. UV-C radiation causes eye damage and skin damage, there are reasons these LEDs are expensive. Don't buy UV-C LEDs from greymarket sources (like eBay or Alix), they will most likely be fakes that actually emit UV-A or something similar.

author: tooki
author_rank: Super Contributor
timestamp: August 15, 2020, 01:23:51 pm
content: Quote from: justageek on August 15, 2020, 09:21:19 amYou may want to consider why they only used 5 LEDs, though: genuine UVC LEDs are really expensive. The cheapest one on Digi-Key under 280nm is $4.50@20.

author: zenerbjt
author_rank: Regular Contributor
timestamp: August 15, 2020, 04:56:08 pm
content: For high step-up ratios, use constant off time ...........or constant frequency in a "dual cascaded booster" with a single controller.HV9910B is a good constant off time controller

author: justageek
author_rank: Newbie
timestamp: August 17, 2020, 03:18:25 am
content: Thank you everyone for your helpful advice. I will try the design.

author: MarkR42
author_rank: Regular Contributor
timestamp: August 18, 2020, 04:17:13 pm
content: I made a thing with 26 (mostly red) LEDs and I used a step-up boost converter to run them on 2xAA cells, I used the small MT3608 chip used in many ebay/aliexpress boost modules to boost up to 5.6V