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Help with power options please

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  • Help with power options please

    I'm going to be putting in a tablet in my car, Samsung Galaxy 10.1 and I need to be able to charge that, an HDMI converter, a Headphone amp (for volume control), and as well my phone charger (Galaxy S3). The Headphone amp, and the HDMI converter run with a regular wall plug. Those need converting to be able to run in my car. But I also don't want to have to run the tablet and phone off a couple of cigarette lighter adapters.

    Can someone assist me with what I need and how I would go about hooking it up? Thanks!

  • #2
    Unless those devices have a 12V vehicle compatible input, you won't be able to use a cig socket anyhow.

    The options include getting a suitable cig-socket adapter for each item (which can be hard-wired instead of using the socket) or suitable dc-dc convertors, or a dc-ac inverter to provide a suitable AC output - probably a 150W or smaller inverter will do.
    The inverter will probably need to powered direct from the battery with its own fused cable, and I'd suggest a relay to switch on & off. The relay can be switched by various means (eg, ACC, IGN, only when charging, manually, or any combination thereof).


    • #3
      For the cigarette lighter or input or whatever you want to call it, I was only speaking of the phone and tablet cause they both have the in car charger ability. The other two items, HDMI converter and Headphone amp, do not. So I need to convert it, but I don't know exactly what to use. Could use some help with that.

      Can you give me some models that would be best for this?


      • #4
        Will something like this do the trick for the head phone amp and the HDMI converter? IF so do I need two of them, one each?


        • #5
          The first thing is WELL DONE - you have considered a dc-dc converter that is suited to car 12V systems as opposed to "12V converters".
          IE - a "12V converter" etc may mean just that - it requires a 12V input - say 12V +/- 0.5V etc (11.5-12.5V) - aka "regulated" 12V output.
          12V battery systems and in a vehicle's 12V system is not regulated. (Do not confuse the alternator's regulator - that is set to output typically up to 14.4V to charge the battery, and the alternator's output is the "12V" vehicle's actual voltage.)
          And of course you considered quality mp3car products!

          That might be overkill though. I was thinking more along the lines of Current-Logic's DC-DC car converters. (Note the usual "design spec" for car loads to able to handle a 8V - 16V range. Good products might handle as low as 6V and have higher max voltages.)

          You'd need one converter for each output voltage you require. I suspect your tablet requires 12V else maybe 19V etc. Others might have 5V inputs, or 3.3V or 8V etc.

          And each converter must be able to handle the load of the device (Amps or Power).
          Same-voltage loads can be off the same converter provided the total load is likewise within the converters specs.

          If you already have 2 suitable cig-socket converters, maybe getting the same for the others is better. That may also avoid warranty issues.
          But there are various after-market converters - eg, last night I finally used my dual 110-240VAC & 12VDC input 100W "universal" converter with selectable 12V - 24V that I bought ages ago for $25 (normally AUD$45).

          If I used the Current-Logic converters, I'd probably get an extra of each as they are IMO an excellent price (~$20 each). But that's because I like to have a spare. Otherwise my fallback is usually the device's original AC adaptor plus a small inverter. Though that may not be your intent, I mention it as a consideration because - although not ideal - an inverter with standard AC adapters is often the cheapest way to solve power problems. Then as one obtains the proper dc-dc converters, the inverter can be used as a fallback if any fail.

          But you need to fine the required input voltage for each device AND their load - ie, current or power draw (sorry, I have no idea). Same voltage input devices can use the same converter - just add their individual powers or currents to get the total required.
          [Note that in borderline "total" situations, some device ratings are maximums that include battery charging (which drops when the battery is full) or peak current which may only occur at start-up, or assumes all bells & whistles are included and turned on.]

          How to switch on those converters is another issue and may determine if you supply same-voltage devices from different converters. (eg, the IGN, ACC, 12V, manual etc I mentioned in my first reply).

          PS - low voltage low current devices (eg, up to maybe 8V and 1A or 1.5A) could be handled by various "three terminal regulators" (~$3) but that involved soldering and some extra componentry. Plus that is "linear" stuff as opposed to the "switching" or SMPS converters you & I have linked. Switching/SMPS types are typically 90% efficient and run much cooler. Linears are under 50% efficient for the low voltages I mentioned.)
          Last edited by OldSpark; 11-20-2012, 09:11 PM. Reason: PS ...


          • #6
            Wow, that's alot of info. I'll have to go back and re read it and process it.

            I will take pictures, and get specs on all the components I'm going to be running. However, if I could somehow power these units without using those bulky power plugs, then it would make installation much easier and much cleaner. I just want to be sure I understand what I'm doing before I do it so that if I have any troubles down the road, I know what to look for.

            Thanks. I'll get those pics and specs tonight.