elbekko Posted June 19, 2013 Share Posted June 19, 2013 I've been thinking about making a little plate with USB charge ports to go instead of the ashtray in my P38. Some devices, like my phone, can draw up to almost 2A, so it'll need a beefy voltage regulator. I found the LM350T regulator at Conrad, which can supposedly handle 3A+: http://www.conrad-uk.com/ce/en/product/176052/ Also found some USB ports: http://www.conrad-uk.com/ce/en/product/738792/ And made up a drawing in Solidworks of the plate: And what it would look like with 5 regulators mounted and some USB ports (very rough): Having this plate 3D printed in alumide would cost about €25. I'd have it printed in alumide instead of ABS in the hopes that it'd conduct heat a bit better. There's a few vents to let out possible heat from the regulators. So... tell me why this is a daft idea that'll never work please, before I start ordering components. Also what I forgot (some circuitry to "configure" the regulators is needed too, plenty of room for that I'd think). Quote Link to comment Share on other sites More sharing options...
TSD Posted June 19, 2013 Share Posted June 19, 2013 I could go on for hours about all the things wrong with the various 3 terminal ic regulators, but I won't I'd choose a fixed 5V output device - no fiddling about setting the output voltage, and you can get one where the mounting tab is ground, which simplifies the mounting. Don't forget the input and output capacitors as specified by the device manufacturer - they are not all the same. At 2A output, you'll be dropping 8V across the regulator, 16W of heat is not insignificant. A couple of quick sums says you'll need a heatsink around 4C/W, preferably better (lower number). Have a look at the catalogues to gauge what that means... e.g. this one isn't good enough So yes you can, but expect hot and sweaty and/or large metal heatsinks. Don't forget you may need it to indicate to the phone that it's a high power source - usually (but not always) this means shorting the D+ D- pins on the usb socket. Alternatively something like this might be simpler, and certainly run cooler because it a switching regulator, much more efficient than a linear one in this application. Note that one says not suitable for Ipad/Iphone, but doesn't say why that is. Possibly it's just lacking the d+ d- short in the socket, but there could be many other reasons. Switching regulators come with their own set of problems though - usually noise on the radio/cb/phone is the one that gets noticed first. Quote Link to comment Share on other sites More sharing options...
gadget Posted June 20, 2013 Share Posted June 20, 2013 Definitely go with the buck/switching regulators. The one TSD links to would do the job. Bear in mind that anything from china with its random CE mark may or may not be electrically noisy, so buy one and try it before you buy a handful. If you're thinking of building your own i think i'd try an LM25117 http://www.ti.com/lit/ds/symlink/lm25117.pdf Quote Link to comment Share on other sites More sharing options...
elbekko Posted June 20, 2013 Author Share Posted June 20, 2013 Thanks for the input TSD, that's why I posted this I figured they'd be putting out a lot of heat, hence the metal-ish plate and mounting tabs - but apparently that won't be enough then... Indicating to the phone that it's a power source should indeed be just connecting the D+ and D- on the plug. At least that's what the USB charging spec says. I don't have any Apple products or want to come anywhere near them, so that's no problem The one you linked, any chance I'd be able to just buy that rectifier, without it being waterproof and the USB lead? There's a few of them on Conrad, but can't really make sense of the specs... Quote Link to comment Share on other sites More sharing options...
Deej Posted June 20, 2013 Share Posted June 20, 2013 I also agree about going with a switching regulator. Linear regs are simple/cheap but not much good when you need to drop a large voltage at high current. Even with a 4deg/W heatsink, which is already pretty big, it would theoretically hit 64 degrees above ambient. On a warm day that means your metal plate would be well over 80 degrees which would hurt if you touched it. If the heatsink is in an enclosed space it will get even hotter. Quote Link to comment Share on other sites More sharing options...
RJF Posted June 20, 2013 Share Posted June 20, 2013 You'll need a PCB or something similar to mount those USB connectors as well. If you want a quick, easy switching regulator it might be best to look at one of the pre-made modules. These are available in simple 3-pin packages. I've used Recom ones to replace 78 series devices in the past and was quite impressed. Try here... http://uk.rs-online.com/web/p/switching-regulators/7577239/ ... Although this is only a 0.5A part. The solution I went for in the end was to mount a Griffin Powerjolt Dual into the dash (Freelander) as it sits flush and provides a pair of 1A USB ports. http://store.griffintechnology.com/iphone/powerjolt-dual-universal-micro I do like the look of your plate though, so I'd be tempted to mount several of their PowerJolt Micros to it (providing that you can find them for sensible money). Then you'd just need to connect up 12V. If you're 3D printing the part, you could recess them behind the panel to hide the plasticy bit. Rob. Quote Link to comment Share on other sites More sharing options...
elbekko Posted June 20, 2013 Author Share Posted June 20, 2013 You'll need a PCB or something similar to mount those USB connectors as well. I thought I'd be able to drop them into the hole, and then lightly glue them in or something. Then solder some cables to the pins. If you want a quick, easy switching regulator it might be best to look at one of the pre-made modules. These are available in simple 3-pin packages. I've used Recom ones to replace 78 series devices in the past and was quite impressed.Try here... http://uk.rs-online.com/web/p/switching-regulators/7577239/ ... Although this is only a 0.5A part. I can find a 1.5A one: http://www.conrad-uk.com/ce/en/product/154987/ But that's slightly underrated, I'd like to get at least 1.8A. The solution I went for in the end was to mount a Griffin Powerjolt Dual into the dash (Freelander) as it sits flush and provides a pair of 1A USB ports. http://store.griffintechnology.com/iphone/powerjolt-dual-universal-micro The price and 1A rating of those is exactly the reason I wanted to make my own! What would work too is a bigger single regulator that has a max of 15A, ish. I'd be happy with 10A too. The chance that all ports are full and are pulling max load is pretty slim. Something like this, but then in a better form factor: http://uk.rs-online.com/web/p/dc-dc-converters/7603366/ Quote Link to comment Share on other sites More sharing options...
Deej Posted June 20, 2013 Share Posted June 20, 2013 What would work too is a bigger single regulator that has a max of 15A, ish. I'd be happy with 10A too. The chance that all ports are full and are pulling max load is pretty slim. Something like this, but then in a better form factor:http://uk.rs-online.com/web/p/dc-dc-converters/7603366/ The only problem with larger units like that is there will be a fair amount of external circuitry to add in, as the components like filter capacitors become too large to fit in an integrated package. This would probably produce the best end result but there will be more work for you to do. The 1.5A integrated part will be so much easier to work with as it's essentially a direct replacement for a standard 3 pin regulator. Just a shame there isn't one in a higher rating. Quote Link to comment Share on other sites More sharing options...
nicksmelly Posted June 20, 2013 Share Posted June 20, 2013 http://www.ebay.co.uk/itm/23mm-Car-Charger-DC-Voltage-Regulator-Converter-Module-12V-To-5V-3A-15W-F8s-/300912706962?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item460fcb8592 Quote Link to comment Share on other sites More sharing options...
bishbosh Posted June 20, 2013 Share Posted June 20, 2013 I'm clueless about the electrikery, but can you really see yourself needing five USB ports on the go at once?? I would have thought two would have been plenty! Quote Link to comment Share on other sites More sharing options...
TheRecklessEngineer Posted June 20, 2013 Share Posted June 20, 2013 I'd have thought you'd be better off building 5 x separate voltage reg circuits rather than one big one. Looks good though, and exactly what I did in my Volvo. I just had the one though. Quote Link to comment Share on other sites More sharing options...
elbekko Posted June 21, 2013 Author Share Posted June 21, 2013 http://www.ebay.co.uk/itm/23mm-Car-Charger-DC-Voltage-Regulator-Converter-Module-12V-To-5V-3A-15W-F8s-/300912706962?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item460fcb8592 That looks good! Dimensions may be manageable too, will have to plop it into Solidworks and see... Worst case I go to 4 ports, or have 2 "low current" ports that share a regulator. I'm clueless about the electrikery, but can you really see yourself needing five USB ports on the go at once?? I would have thought two would have been plenty! I could probably get away with 3, but I'd rather have some overkill than needing more later. Just off the top of my head: - my phone - friend's phone - gpsmap That's already 3 devices, of which 2 can draw pretty high current. I'd have thought you'd be better off building 5 x separate voltage reg circuits rather than one big one.Looks good though, and exactly what I did in my Volvo. I just had the one though. Yeah, that's what I thought too, but if I can't find them... Quote Link to comment Share on other sites More sharing options...
henk Posted June 21, 2013 Share Posted June 21, 2013 I could probably get away with 3, but I'd rather have some overkill than needing more later. Just off the top of my head: - my phone - friend's phone - gpsmap plus: - separate gps tracker - gopro - photocamera For Iphone/Ipad see also: http://timothyb.net/DIY_iPad_2_USB_Charger.html Quote Link to comment Share on other sites More sharing options...
Orgasmic Farmer Posted June 21, 2013 Share Posted June 21, 2013 Can you not install an onboard PC and use that to power a load of USBs? Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted June 21, 2013 Share Posted June 21, 2013 Somewhat overkill, in terms of sledgehammer to crack a nut, and most motherboards, especially small ones, are only rated to 500mA per output. Quote Link to comment Share on other sites More sharing options...
elbekko Posted June 21, 2013 Author Share Posted June 21, 2013 Those eBay rectifiers are massive when plugging them into the model! I could maybe get away with mounting 5 of them if I cut off the mounting feet and glue them on (or put locking clips in the model). Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.