Can I bury this SMPS DC/DC converter in the roof of my car? - Page 1
Forum section: electronics / projects

author: Fingerpuppet
author_rank: Newbie
timestamp: May 17, 2014, 02:26:10 am
content: I've tried searching, but haven't been able to find a similar project to mine.I want to hardwire in a USB mini B cable to the area by my rearview mirror in my car for powering a mobius dashcam. My car is a 2013, so the courtesy lights and maplights provide 12vdc power that is switched on from when the car is unlocked until 30 seconds after the car is locked.I have room above the headliner to add a DC-DC SMPS, and TI makes an evaluation board that seems to fit the general specs...http://www.ti.com/lit/ug/slvu163/slvu163.pdfAnd it's just US$10.I know it would work, but I have some concerns...1. Heat. It's bound to get SUPER hot up there in the summer... so the 90% efficiency is a big deal, but will it be good enough?2. Total load. I swapped out 3 of the 5 bulbs on the circuit with LEDs to make some headroom, but up to 10 watts isn't nothing.3. Noise. I know most USB cigarette lighter adapters aren't isolated. This isn't either. Will it be a problem?4. Safety. I will probably put an inline fuse up there. How big should it be? 2 Amps? 5 Amps?5. Filtering. Is the stock LC filter adequate? Is there any reason to consider a larger input cap?Thanks for your help, I'm sorry I don't know more of the answers to my own questions.

author: David_AVD
author_rank: Super Contributor
timestamp: May 17, 2014, 03:20:52 am
content: I installed a cigarette lighter socket (and a 2A fuse) in the roof area of our service van to charge the GPS unit (mounted high up on the screen) via the original adapter and cable.It's been in there for about 18 months now. The van sits outside every day.

author: nihilism
author_rank: Regular Contributor
timestamp: May 17, 2014, 03:55:08 am
content: I'd say it would be ok. I would definitely go with the inline fuse and do some testing before making the install permanent. You should be able to get an idea of if the converter itself will generate enough heat to be an issue.

author: bing_commander
author_rank: Newbie
timestamp: May 19, 2014, 05:04:30 pm
content: I have that same camera in my car. I tucked the wire into the headliner and down the a pillar to the fuse box by the drivers foot. That way, I could use a fuse tap to avoid chopping the wiring in my new car. It's cooler down there, and you also get a choice of any circuit. My car had a unused circuit to tap.

author: Isad
author_rank: Frequent Contributor
timestamp: May 19, 2014, 05:12:10 pm
content: Well give it a try you cant loos any thingand as long as you dont live in africa you will be good

author: gxti
author_rank: Frequent Contributor
timestamp: May 19, 2014, 05:27:07 pm
content: Great idea, I've been meaning to build a custom dashcam setup for my car but this post inspired me to just buy a Mobius and make it work. If it goes well I might buy a second one for a rear-view backup camera type setup, it looks like I can get composite video out of the USB connector so all it might need is an extension to run to the back of the car.I agree that it probably makes more sense to put the voltage convertor in/near the fusebox, you can probably find one or more "courtesy light" circuits there to tap into and it also gives you the option of routing the video somewhere too.

author: Neverther
author_rank: Regular Contributor
timestamp: May 19, 2014, 06:25:49 pm
content: 2.5W draw if it follows 500mA max spec. Even 20% of that going to heat is nothing if the converter has any mass at all.I have chinese "LM2596" board stealing power behind cig lighter (switched). Cable routed behind dash and A-pillar trim to the sunvisor.Sunvisor has two mini-Bs, one for GPS and one for Mobius/808 #16. GPS is attached with velcro and Mobius is just tucked between rooflining and sunvisor, cant leave anything into car.Haven't had any problems as those cheapos can supply 2A without too much of a problem. 5V power cable is long, but as those two draw 1A max, its not a big deal.One thing chinese cheap out on those modules is ceramics on output as there is usually just some noname electrolytic installed, 28V typical max input is enough for automotive useOne thing that sticks to eye is 10V min voltage on that TI converter.Better have fresh battery that doesn't sag on startups.I've managed to "brown out" the mobius during winter starts on old battey (ign on -> mobius powers on -> start as mobius is about to start recording -> voltage drop -> mobius stops and turns off -> car starts -> mobius still off). Replugging the mobius restarts recording as I have auto recording on power.

author: gxti
author_rank: Frequent Contributor
timestamp: May 19, 2014, 09:56:31 pm
content: Definitely lower minimum voltage is better. I've got some Murata modules that are drop-in replacements for linear regulators, they do 7-36V in, hopefully that does the trick. I was going to add a low voltage cutout but I'm not really interested in running the camera while the car is off, so wiring into a lighting circuit that is already switched off sounds like a great idea.

author: Fingerpuppet
author_rank: Newbie
timestamp: May 20, 2014, 03:48:13 am
content: Quote from: bing_commander on May 19, 2014, 05:04:30 pmMy 2013 Sonata has side airbags aplenty, so the "A" pillars are a trick bag. I'm not that adventurous.Quote from: Isad on May 19, 2014, 05:12:10 pmI did for a year, but not anymore.

author: TheBorg
author_rank: Frequent Contributor
timestamp: May 20, 2014, 04:07:13 am
content: You could just do what my friends always seem to do, and just route a cable along the outside of the car and through the door seal and hot glue it to the interior