2012-05-29

Getting the electrons from my drill into my phone.

I enjoy camping up with My girlfriend and all of our friends.  We very much enjoy listening to Music while up at camp.  I don't want to steal music, and I can't justify buying music that just isn't that good.    I like Podcasts, Matt Paxton of Hoarders is one of my favorite ones to listen to these days.  He has a very honest show, but it is adult content that some knee high campers should not listen to.  So we always end up with Pandora which is great and we can all enjoy the variety of music and find new things to share and enjoy.  For like 4 hours till my phone dies.  Droid Razr with a tiny Battery it comes with a 3.8 volt 1750mA battery pack which is 6.7 Watts.  That means I am using up about 1.5 watts per hour to listen to the smooth vocal styling of Nina Simone.  I Picked up two portable Power Packs on Woot which were great, but with similar power densities I am trying to refill a leaking 1 gallon jug from another one gallon jug.  The best I will ever get is two gallons (14.25 watts) of Music.  

We set up a 12 volt battery with an inverter last time, but it was heavy and I don't like having open battery terminals with the little campers around.  So I started to figure out how to make my 19.2 volt (20 volt) Drill batteries plug into my phone.  The phone will work directly off a usb power supply which is nominally about 5 volts and the drill battery is either a 4 or 5 cell lipo pack.  Around 16-20 volts depending on the cell count.  I am guessing the pack is around 3AH based on weight so I have about 60 watts of power, or 10 times the power in my drill pack if I can get it from efficiently from the Big battery to the little battery.  I immediately went back to my Battlebots days 7812 +12V Voltage Regulator and 7805 +5V Voltage Regulator I used to make receiver battery eliminators.  They worked fine when I was drawing 50mW for 5 minutes of duty cycle.  I checked the input voltage max and it was 35 volts. I started thinking I would just get the 7805 and go from the battery to the 7805 to the usb plug.  Paul saw my idea and immediately pointed out it would overheat. Not like I would listen to that gibberish.  I went out to find my trusty 7805 regulator so I could charge USB devices and 7812 so I could charge things that run off a 12 volt accessory outlet in a car.  We hit Radio Shack and they still had both in stock. They did not have a usb outlet and it would be a minimum of 20 bucks for anything with a female usb connector.  We went to target, I was hoping I could find something cheaper or a hub or something.  I found a power block for the car that would do 12 volt sockets and two usb sockets for 15 bucks.  I thought I may have lucked out and found a setup with a 5 volt regulator I could use.  It was, but it had a 15 volt max input.  Since I could have up to 22 volts coming in, I would need to regulate down more.   



Pulled apart the 12 volt in would need a 12 volt regulator to operate most cell phone chargers and the usb adapter board.
"Use only for original intended use.  No user serviceable parts inside.  Altering or tampering with the product or any of it's components may result in shock, fire, product damage, and or vehicle damage."

Craftsman C3 light being disassembled.  It already has the power connections for the battery and a switch.  Why re invent the wheel.  


Circuit all built up and being tested on a power supply.  works great on the single led USB light.

Beta packaging.  I want to test it before I 3d Print a better housing.  
And it did not work.  I took it up to camp with me and tested both halves of the system.  the 12 volt output to a phone charger and the 5 volt output via usb.  Both registered as the proper voltage output, but could not dissipate the heat enough to charge my phone.  I got home today and took everything to Make It Labs to try and figure out what to fix.  As soon as I opened the case, I could see the shrink wrap had failed and torn from over heat.  Paul helped me find a to220 heat sink and I cut some components out of the system so it went Battery > fuse > 7812 regulator > on board 5 volt regulator. I got this all put together and hooked it up for a test ride.  The battery charged at a rate above 1 amp with a darn warm heat sink.  Now I just need to package it better.  For longer term use, I will need to find a better way to disiapate heat and possibly got to a more efficient (looking at a buck regulator)


Electrons flowing.  

Close up of the scavenged usb board and 12 volt regulator.
I am now looking for a better regulator that will be able to operate cooler with more power throughput.   I want 8 amos at 5 volts and 5 amps at 13.8 volts.  Please comment if you have any recommendations.

1 comment:

gary gates said...

Ummmm ok. I didn't understand half of what you wrote about. But as for your heat problem. Any way you could install a small fan or openings to let the heat out. Small holes in the case maybe.