Slashdot Mirror
Replacing All of Those Pesky Power Adapters?
bobrobins asks: "I'm sitting in a hotel with a desk full of chargers: laptop, mobile phone, walkman, camera, electric razor in the bathroom, and a laptop supply for the plane, oh and one for the new sony speakers. Before you say too much I've been on the road for a long time and need them all! There must be more gadget geeks out there with a better solution, really all i need is a single charger/power supply that can charge all of these maybe 2 at a time. Any ideas appreciated - my back hurts from lugging this lot around!"
I've wanted something like this myself--but not for nearly as many devices. The basic problem is that there isn't really any standards across all manufacturers or devices. Think about your power requirements in more detail:
Regardless, only you and maybe 50,000 other people have those exact same devices. For a company to design something for such a small market, they would need to charge an arm and a leg (and then pray people would buy it). Most people just deal with all their chargers.
Most people. But you're a nerd, geek, whathaveyou. You can't have all these chargers because you know there's a better way. And you're right.
Okay, my problem was that I had a laptop, nice external speakers, a small 5-port 10/100 switch, and my Palm. The laptop needed 19VDC at 75 Watts, which was by far the most demanding item I had. I picked up an electronics book that showed how to make a good AC-DC power supply from the library and then got a Jamecocatalog and worked out all the parts I'd need. I ended up needing a really big board for just all the parts to the 19V supply, but I could sqeeze in the other supplies I needed (5V and 12V) without too much trouble. Then, put the whole mess into a vented box and into my laptop bag. Now I just plug my bag into the wall and everything starts working. The whole deal probably cost me a hundred or so, but it sure makes everything look nice.
Long, cute, or funny Sigs are just another form of over compensation, used by geeks, nerdz, etc.
My laptops require anywhere from 19 volts to 15 volts, but you know what? They all have switching power supplies to convert the power feed into the varying degrees of power needed for the CPU, bus, multiple batteries, disc drives, and inverter for the screen. I have found a fused connection from a car battery is more than sufficient for operating my laptops. Even with a voltage swing from just under 12 volts up to 16 volts from starting the car to taking long trips, the laptop, even with its battery removed, will keep on going.
Just be sure to fuse the connection around 6 amps or so. There should be a diode inside the laptop in case the polarity is reversed, so that fuse is necessary. Be aware that switching power supplies will draw more amperage when the voltage is lower. The only two exceptions is the low voltage alarm that will be triggered before the CPU is starved of voltage required for proper logic levels or the high voltage SCR "crowbar" which will clamp down on dangerously high levels.
Oh, I suppose experimenting with crude power feeds to your delicate electronic equipment will weed out inferior designs. Great experimenting on cold winter mornings. The worst that could happen is you could start a nice toasty fire to warm your hands and lap with.
>For the KVM switcher that needed 9 volts, I tried using the 7 volt level, which almost worked, but not well enough, so I took the 12VDC line, dropped a variable resistor on in a voltage adjustment (not rheostat) config, measured with the DVM for the proper voltage (a little over 9VDC), then tried it - it worked fine. I let it run for a while, then felt it for heat - not too big a deal, ran cool. I could have also dropped the voltage to 9 volts over a few diodes as well, or if I wanted to be really cool - use a variable regulator circuit. But this particular device didn't need it.
Uhh. Your voltage will vary with your load - it suits you to use a voltage regulator. Use an LM7809 and attach it to your 12Volt line and ground. You should be able to get these from jameco or even radio shack.
fnord.
I agree that we need a new low power standard. I have often thought that new homes should be built with a 12V socket next to every mains socket. Each home would then need only one 12V power supply next to the fuse box instead of all these ugly seperate wall-warts. All new electronic devices should use a standardised plug and convert the 12V into whatever they need.
Steve.
A latent existence
You can also get a similar cable that charges those Palms that run on rechargable batteries.