adding interior led lighting

Hello All, Just joined this forum as it seem to have a fountain on information. I am from the UK. I have a HONDA CRV 2002 MK2 I want to add interior LED lighting in the footwells of the car that come on when i am driving the car. The best way i can easily see to achieve this is from my cigarette lighter as this only turns on when the Ignition key is on. I have found LED strip lighting on ebay that is 12v Here is the link for more information Ebay I currently have LED lights in my car that use a USB connector. My cigarette lighter has a DUAL usb adapter so i can charge my phone and run these usb lights. Looks very messy. Now i am an IT engineer and i believe that USB socket on a PC draws 5 volts, no more. So would i be correct in saying that the USB led lights are only using v5 ? I want to get rid of this as it looks messy, so if i purchase these led lights from ebay, am i correct in saying that i can connect the positive and negative of these LED stip lights to the positive and negative on the back of the cigarette lighter ? or do this but with a Inline fuse aswell. I might want to add a in series switch so i can turn them off whilst driving aswell. Do you think there will be a limit on how much LED lights i can put on the cigarette ligter. Just in case i decide to add more LED lighting to the car at a later date, ie the rear foot wells. at the same time as the front footwells. Please correct me in any way , i am quite good with a soldering iron, just not to ok with calculating what parts i need to achieve what i want. Thanks in advance Rob.

Yes, the USB LEDs are only 5V. You can't feed raw cig socket 12V to your 12V LEDs as the cig socket is "automotive 12V" which typically means anything up to ~14.5V and sometimes higher. Your LEDs are (presumably) 12V LEDs which typically means 12V +/- 0.5V. To preserve your LEDs you'll have to add a voltage regulator else use a voltage limiter, or maybe a series resistor. The latter 2 aren't suited to higher currents (ie, 1A etc). I'd suggest a cheap buck (step down) SMPS converter set for 12V. These are a $few off eBay. Tho cig sockets are rated up to 15A, few handle such high currents without melting or flaming. Most OEM cig sockets are probably fused at 10A. However 3A should be fine and that's enough to run two of your 5m LED strings. A fuse is only required to protect your wiring - ie, from the cig plug. A fuse will not protect the LED strips. FYI - For resistive loads, a 14.4V supply (12% higher than 12.0V) means the load consumes 44% more power than at 12V and that's enough to destroy most "12V" loads. LEDs are similar except that it's usually worse - the 12% higher voltage can mean more than a 12% increase in current.   

Hi thanks for the reply. This sounds a bit complicated lol. how come i can use the one i have now that's connected via a usb connector. not really sure how to achieve this now without setting fire to everything

Because your USB LEDs are 5V and USB is 5V. Your USB adaptor - probably one of the SMPS converters I mentioned set to 5V - regulates typically 6V to 20V down to 5V. Maybe just use a resistor - eg, 1.5 Ohm 5W for a full 1.5A string.

arghhh ok not good. would it be the same case if i used these ? ebay

Ask the seller. It states "12V" but the title says "car", so does that mean "12V automotive" (as in up to 14.5 or 16V?) or 12V as in 11.5 - 12.5V etc? Be aware that being "automotive" merely means larger internal resistors so that max current occurs at (say) 14.4V instead of 12.0 or 12.5V, but brightness will vary with voltage. Hence if constant brightness irrespective of engine running etc is paramount, then voltage regulators/converters are best.    FYI - that was the beauty of some 27W 1450 Lumen LED spotlights I recently sampled - brightness was constant from ~10V to 15V. PS - another method is current limiting using an LM317 plus one resistor. The problem however with series current limiting circuits (LM317) and resistors (eg, 1.5 Ohm 5W) is that as downstream LED strings fail, the remaining get more proportionally current, hence you can get "over-current collapse" runaway. Not that slight overcurrents immediately kill LEDs; they merely reduce their life. But hence why (1) it's usually one resistor (or current limiter or ballast etc) per LED strings, or (2) a single current limiter for multiple parallel strings is often sized to provide less then the max allowable current.

After a night's sleep... I reckon go for whatever LEDs suit what you want - ie, 5m (16') rolls if you want lots of LEDs cheap (cut to length), or smaller ready made strings. It depends a lot on what behavior you want, but my thoughts were f.ex bright footwell or cabin LEDs when door(s) open which dim with IGN on or engine running etc. The control & wiring is one thing - ie, switching logic; timers/delays; cig sockets, etc... (Obviously not thru an IGN controlled cig socket if used for puddle or entry lighting.) But all things considered, I reckon a buck/boost (up & down) voltage converter. Previously I mentioned buck (step down) converters. EG - eBay item 301141136559 shows FIVE adjustable 3A converters for AUD$4.99 (plus ~$1 postage) - hence a bit over $1 each. I doubt you could buy older linear converters for that much (LM7812; LM317, etc). However the problem with all such step downs (SMPS using LM2596S or LM2577 etc, or linears like LM78xx & LM317) is their own voltage drop which is typically 1.5 - 2V. (Low drop-out versions are available which may have a 0.2 - 0.5V drop.) If a 1.5V drop, then on a full battery (12.7V) the LEDs will get 12.7-1.5 = 11.2V. In fact they won't get their "full" 12V unless charging exceeds 12+1.5 = 13.5V - ie, engine running. Now for ~$3 to $4 each you can get equivalent buck-boost converters - eg eBay items 380805107821, 301218785312, 181441926665. So imagine impressing your partner, pickup, or favorite program as you get in the lit cabin and the LEDs do not dim even when the battery hits 9V during cranking! (If only they were RGBs that color changed as moods swing.)    If dimming isn't an issue, then IMO add a series resistor to any "12.0V" string - eg, R = 2.4/i Ohms where i = string current, and assuming 14.4V max voltage. But be aware that losing LEDs means increased current to the others. Plus the resistor dissipates heat - eg up to 2.4V x 1.5A = 3.6W (1.6 Ohm) for a full 5m 1.5A string. But since high power resistors get hot and can cost a bit, I'd consider those SMPS regulators/converters anyhow. For LEDs with constant brightness irrespective of battery & system voltage, cranking, audio burps etc, then buck/boost converters. But hunt around for converters. All the converters I provided eBay item numbers for should handle 2A and hence your full 5m 600 LED string. AND they use a multiturn thru-board trimpot for accurate and stable output adjustment for automotive applications. Being non-SMD is handy if you want to switch in - or out - parallel resistor(s) to change output voltage and hence LED brightness. Be aware of converter ratings. Many are "3A" IMO are 2A output etc - their 3A output may require a heatsink etc. Some may be "n Amp" capable but limited to a certain power output - eg 3A but 18W means 3A @ 5V but only 1.5A @ 12V. Some feature both thermal/overcurrent & shortcircuit protection which should solve rating issues. With reverse polarity protection they should be indestructible. Circuit (PCB) size decreases with increasing converter frequency, and so usually does efficiency, but efficiency depends typically on currents involved. If running two 1.5A strings, I'd prefer a separate 3A converter for each, else a 5A converter to simplify dimming - tho probably separate converters for on-off cabin LEDs and on-dim-off footwell lights. Anyhow, sorry to throw all this at you, but it may provide some accelerated wisdom & ideas. (Hence the ultimate or better future-proof bling or functionality now instead of a later replacement.)    Also what were once the simple & cheap solutions may no longer be cheap compared to the ultimate solutions - even if initially they may still be far from simple to understand. As an afterthought, IMO the most difficult thing about LEDs is their connection. If cutting or connecting LED Flexible Strips, I highly recommend obtaining their matching (pre-wired) connectors. (Even my soldering had issues, and I hand-solder SMD ICs!) Be aware that the connector must match the Flexible Strip. They may look the same but vary in width, conductor pitch & number. Typically available in prewired lots of 10 or 20 etc (on eBay). BTW - those step down converters are almost as cheap in one offs. But I suggested a 5-pak to mortise postage, and so you have a supply of 2A automotive USB supplies and phone chargers at $1 each (excluding connectors etc).      FYI - below is a pic of the bucker I'm using for my combined stop/tail 3rd Stoplight LED bar. (1.2MHz switching frequency; 1.8A, ~$2 each; from eBay's axeprice who resent my original 20-item order FREE of charge after Australian Customs lost my package.)

PS - I mentioned eBay's axeprice in my last reply. Unfortunately I didn't check their site before I gave those eBay item number examples. Tho axeprice's currently presently available step up/downs are only rated for 1A, or 1.5A with heatsink, they too have suitable converters, and I dare suggest at better prices than the examples I gave. Not that I mean to push or promote axeprice - please do your own searches etc - but for those that question eBay suppliers... (Like seriously - who would resend an order without request and without charge? Well, axeprice in Shenzhen China did! And not that I've used all my order, but even the small converter pictured has been operating for over 4 months with mere conformal coating (except over the trimpot) wrapped in some electrical tape (with hole for pot access) and bridged between floating wires beside the radiator in my 49 year old bush-bashing & daily-drive ute.) I initially didn't think of axeprice because I searched by image for thru-hole multiturn trimpot with easy or rugged DIY features etc. My axeprice converters were either small high-frequency else high current switchers. Again, apologies for the sales pitch. I'm not into selling tho I strongly believe in supporting good suppliers products.

How about opening up the converter you have currently, and run wiring directly to it? This would save you a ton of time, etc. You could also run the lights you currently have. Add a second converter, open that one as well, and mount the USB receptacles into your dash or somewhere for a built in appearance and to be used with your phone, tablet, gps, etc. Not a perfect solution, but some times simple works.Webpager - Upfitter, computer guy, car guy. I can't tell the difference between Columbian or African coffee, but I knew at age 4 the difference between volts, watts and ohms.