Motorcycle LED Power Circuit. Does it looks right? - Page 1
Forum section: electronics / beginners

author: ElectricPower
author_rank: Frequent Contributor
timestamp: January 20, 2022, 04:18:29 am
content: I'm going to install 5V LED strips on my motorcycle and i'm going to give it power from the 12V battery through an XL4015 Buck Converter. The circuit it's pretty basic, but i just want to be sure. Specially regards to the reverse protection diode and the fuse.Is there anything else i should add to that circuit?A little short explanation:+12V from battery, and inn to an XL4015 Buck Converter that gives 5V out. From Buck Converter and inn to an Bluetooth RGB controller. (SP110E).

author: kjr18
author_rank: Regular Contributor
timestamp: January 20, 2022, 08:27:06 am
content: Well, first thing, your battery is in wrong polarity on your schematic. I think you should add some more protection like crowbar circuit or at least some TVS diodes to keep voltage surges from damaging voltage converter, as your power source will be very noisy and probably full of voltage spikes.

author: wraper
author_rank: Unknown
timestamp: January 20, 2022, 08:30:51 am
content: 1N4007 is too weak for something with 10A fuse. It will probably blow up if battery is applied in reverse polarity.

author: Jeff eelcr
author_rank: Frequent Contributor
timestamp: January 20, 2022, 02:28:32 pm
content: 10A fuse seems high to a MC battery. How much current do these strips draw?Jeff

author: ElectricPower
author_rank: Frequent Contributor
timestamp: January 28, 2022, 10:57:24 pm
content: Quote from: kjr18 on January 20, 2022, 08:27:06 amThanks. I will correct thatBut can you please give me an link to an TVS diode that works for general use in 12V automotive circuits? The board i want to protect is an XL4015 Buck Converter.

author: thm_w
author_rank: Super Contributor
timestamp: January 29, 2022, 01:33:52 am
content: XL4015 rated up to 36V 5A, so you could probably use a 22-24V TVS.SA22A or SA24A, if you want through hole.

author: ElectricPower
author_rank: Frequent Contributor
timestamp: January 29, 2022, 02:28:39 am
content: Quote from: thm_w on January 29, 2022, 01:33:52 amThanks. But how much current should the diode take?

author: SmallCog
author_rank: Frequent Contributor
timestamp: January 29, 2022, 04:18:04 am
content: Why not use 12v strips?

author: ElectricPower
author_rank: Frequent Contributor
timestamp: January 29, 2022, 12:14:49 pm
content: Quote from: SmallCog on January 29, 2022, 04:18:04 amBecause 12V strips also need an steady voltage and a 12V battery does not give that. I do not see any reason to use 12V strips vs 5V. But i'm not 100% sure off course.I'm going to need an volt regulator anyway, i think?

author: fcb
author_rank: Super Contributor
timestamp: January 29, 2022, 02:02:53 pm
content: Load dump protection!!!Probably get away with something like a 18-24V TVS and just have a 0R22-0R47 in series with it.

author: ElectricPower
author_rank: Frequent Contributor
timestamp: January 29, 2022, 03:30:20 pm
content: Quote from: fcb on January 29, 2022, 02:02:53 pmCan you explain why not an 0R22-0R47 resistor lets out the magic smoke if the spikes is around 100V?Can someone explain how i can protect my XL4015 regulator against voltage spikes from 12V battery with schematic?Thanks

author: mariush
author_rank: Super Contributor
timestamp: January 29, 2022, 03:44:45 pm
content: A bit unrelated but you'll want to be careful and check the laws in your country ... in some countries it's illegal to have lights that are similar to emergency vehicle lights (that blue of police cars for example) ... white, yellow and red would probably be fine.There may also me some laws / regulation about maximum brightness (so you don't blind other drivers) ... would probably have to use matte / wide angle leds.

author: fcb
author_rank: Super Contributor
timestamp: January 29, 2022, 03:51:45 pm
content: Load dump is a fairly generic phrase, typically something that is 'load dump' protected is also guarded against other automotive transients.https://en.wikipedia.org/wiki/Load_dumphttps://training.ti.com/automotive-transients-explainedI'm not suggesting an 0805 size resistor! Size your resistor to be as large as you can. If you are dumping Vin voltage across a 7805, you might as well dump some across your Rin.

author: ElectricPower
author_rank: Frequent Contributor
timestamp: January 29, 2022, 04:04:05 pm
content: Quote from: fcb on January 29, 2022, 03:51:45 pmBut an 7805 has a max input voltage around 40V. With 100V+ spikes i think the magig smoke appear?

author: fcb
author_rank: Super Contributor
timestamp: January 29, 2022, 04:40:10 pm
content: Quote from: ElectricPower on January 29, 2022, 04:04:05 pmRin in series with Vin on the 7805.TVS/Zener/whatever between Vin and 0V/GND.Under normal conditions you'll dissipate a little bit of power across Rin (lets say Rin=0R47 and your circuit is using 0.25A, Rin will dissipate 30mW).When you hit a spike of say 60V, and your TVS clamps to say 35V you'll be dissipating 1300W for few hundred microseconds, say 1ms = so your Rin has to dissipate 1.3J or power. This assumes you don't loose any across your PCB, wiring, connectors etc..

author: ElectricPower
author_rank: Frequent Contributor
timestamp: January 29, 2022, 05:24:42 pm
content: Can i use this diode?https://www.aliexpress.com/item/33054859529.html?spm=a2g0o.productlist.0.0.8a023594uPyC14&algo_pvid=ef4700c7-b25b-4bdc-9121-96c8d5008ed5&algo_exp_id=ef4700c7-b25b-4bdc-9121-96c8d5008ed5-18&pdp_ext_f=%7B%22sku_id%22%3A%2267449010785%22%7D&pdp_pi=-1%3B7.81%3B-1%3B-1%40salePrice%3BNOK%3Bsearch-mainSearch"1.5KE18CA"My circuit will use absolute max 4 amp. Most likely never over 2 amps.

author: fcb
author_rank: Super Contributor
timestamp: January 29, 2022, 05:37:04 pm
content: Probably OK, although I'd go abit higher with the breakdown voltage, probably closer to 25V - typical 7805 is good for 37V input.

author: ElectricPower
author_rank: Frequent Contributor
timestamp: January 29, 2022, 05:59:26 pm
content: Quote from: fcb on January 29, 2022, 05:37:04 pmThanks alot.I have ordered 18 and 25V TVS version now. 7805 i allready haveCan you give me an simple schematic example please?

author: ElectricPower
author_rank: Frequent Contributor
timestamp: January 30, 2022, 06:26:46 am
content: And how can that 0.47R resistor and 7805 take a max 4 amp continious load?I just can't understand...Can i do something like this?

author: Zero999
author_rank: Super Contributor
timestamp: January 30, 2022, 09:30:11 am
content: Quote from: ElectricPower on January 29, 2022, 12:14:49 pm12V LED strip is more efficient, than 5V strip.12V LED strip consists of multiple strings of three LEDs in series, with a series resistor. Each LED drops about 3V, giving 9V in total going to the LEDs and 3V across the series resistor. 9/12 = 75% of the electrical power going to 12V LED strip, is delivered the LEDs.5V LED strip consists of a single resistor, per 3V LED, 3/5 = 60% of the electrical power going to the LED strip is delivered to the LEDs.Another advantage of using higher voltage LED strip is, the current is much lower, so there's less voltage drop over the length of the strip and cables. With a very long LED strip, the LEDs further away from the power connector, will be noticeably dimmer, as voltage is dropped over the copper tracks in the strip.If you want to use a linear regulator, use 12V strip and a 12V low dropout regulator. The battery voltage should always be 12.5V, except when the engine is being started, so it will output a steady 12V, most of the time.I would use a boost converter and 24V LED strip, which consists of strings of six LEDs, per series resistor and has a similar efficiency to 12V strip, but the higher voltage means a lower current draw.The only advantage 5V LED strip has is, it can be cut every LED. 12V and 24V strip needs to be cut every 3, or 6 LEDs.

author: ElectricPower
author_rank: Frequent Contributor
timestamp: January 30, 2022, 09:51:32 am
content: Quote from: Zero999 on January 30, 2022, 09:30:11 amThanks. I understand that part. I want to use 5V led strip because i want to control individual leds. I also do not need long led strips. Maybe total length of around 1 meter is absolute max. 60 LED/m.My consern right now is the inrush current/voltage that can destroy my voltage regulator (XL4015). I want to protect the regulator from voltage spikes.

author: Zero999
author_rank: Super Contributor
timestamp: January 30, 2022, 05:30:21 pm
content: Quote from: ElectricPower on January 30, 2022, 09:51:32 amHow are you going to control the individual LEDs? Is it addressable LED strip?A buck converter is a good idea, because it has less power dissipation and thus heat.What sort of motor cycle is it?The XL4015 is a good idea. It will be find, as long as the battery isn't suddenly disconnected, whilst it's running. A crowbar and fast blow fuse will provide protection against over-voltage/current.

author: ElectricPower
author_rank: Frequent Contributor
timestamp: January 30, 2022, 08:08:23 pm
content: Quote from: Zero999 on January 30, 2022, 05:30:21 pmIt`s an brand new Triumph Speedmaster 1200 (2022).I'm not going to disconnect it, but i'm going to add an switch between battery and the converter.I'm going to ise an SP110E controller with bluetooth and app functions. Yes, it is individual adressable LED strip. (WS2812B) 5V.

author: Zero999
author_rank: Super Contributor
timestamp: January 30, 2022, 08:36:15 pm
content: Quote from: ElectricPower on January 30, 2022, 08:08:23 pmWhat if the battery accidentally becomes disconnected, due to a wiring fault? The problem with that is the voltage can suddenly rise, before the alternator's regulator circuit has time to react.QuoteThen you should have made the part about the WS2812B clear in your first post. It would have saved a bit of trouble.The circuit in your original post is fine. It just needs over voltage protection and a 5A fast blow fuse. The TL/LM431, a couple of resistors and a TRIAC can be used to make an over voltage protection circuit, which also protects against reverse polarity.https://en.wikipedia.org/wiki/Crowbar_(circuit)

author: ElectricPower
author_rank: Frequent Contributor
timestamp: January 30, 2022, 08:52:21 pm
content: Quote from: Zero999 on January 30, 2022, 08:36:15 pmThanks.Can you give me an example circuit drawing with an LM431, resistor and fuse placement please?

author: Zero999
author_rank: Super Contributor
timestamp: January 30, 2022, 09:19:28 pm
content: It was in the Wikipedia article I linked to but the forum butchered the URL. Here it is fixed. Also Check out the TL431 data sheet: available from all good search engines.https://en.wikipedia.org/wiki/Crowbar_(circuit)