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adri
11-18-2010, 08:07 PM
Hi

I like to mess about with the prop in various locations. It'd be nice to have a power supply that I could move around with that didn't depend on plugging into the mains.

Anyone got any suggestions?

TIA

Adri

WBA Consulting
11-18-2010, 09:11 PM
If you do some searches for battery packs on the forums, you'll find other threads with what people are using. A lot of people use multi-AA holders from places like radioshack, etc. Some (like me) use NiCAD packs meant for RC cars. I have a 9.6v pack from a WalMart clearance shelf. Works great and lasts a long time. It's about the size of the demo board and ~1/4" thick, so it is ideal.

You can see the pack in use on my Reverse Geo-Cache project with a proto board here:
http://forums.parallax.com/showthread.php?t=118830
first picture on post #4 shows the hardware layout

When I use it with my demoboard that's in an enclosure, it fits in the lid for transportation.
http://forums.parallax.com/showthread.php?p=877818

Rayman
11-18-2010, 09:38 PM
If you have a spare USB port, you could just get one of those USB cables that has the barrel connector at the other end...

Ravenkallen
11-18-2010, 09:50 PM
Depending on the amount of devices you have hooked up, you might be able to use a 9 volt battery... If you board is drawing a lot of current you 9 volt will not last long... For most of my prop projects i just use a four AA or AAA battery holder.

Cluso99
11-18-2010, 11:59 PM
Don't use too high a voltage. A 4xAA battery pack delivers 6V which should be fine if you are not supplying a lot of current at 5V.

The best is a 7.2V LiPo battery pack and a cheap charger. Try www.hobbyking.com (http://www.hobbyking.com) for ones used in radio controlled hobbies.

Peter Jakacki
11-19-2010, 12:40 AM
External battery packs? One of the first things I did with my demo board was to bridge the USB +5V to the board's +5V. Rarely do I plug in a external power supply as it gets it's power from the laptop when I travel.

If I do need portable power without a laptop then I just use one of those portable power packs the size of a small paperback that has selectable output voltages (3...16V). But please please don't mention 9V batteries, they are an evil invention.

Bear in mind too that the demo board only needs 5V for the keyboard and mouse so if you are not using those then you could power the 3.3V line directly from two AA alkalines or lithiums as these hold up their terminal voltage well almost to the end. The lithium cell terminal voltage drops down to 1.4V volts when powering a 100ma load after 28 hours. The Prop can operate down to 2.7V.

Mike Green
11-19-2010, 12:46 AM
For those Prop boards that are designed for a 6V to 9V power supply, I use a 4 x AA battery holder from RadioShack, the kind that's enclosed with a built-in switch and fill it with alkaline cells. These days, I mostly use Prop boards designed to run off +5V from the USB connector and I have rechargable USB chargers (one from Solio has solar cells for charging as well as a wall-wart socket) that I use.