USB Charger on motorcyle...

[worwig]

Originally Posted by jmanz6

I just put this together to try out. I'm using 2 7805 5v regulators and am just waiting on the 2 weatherproof USB sockets I ordered to get here. I will mount them to the inner fairing giving me 2 USB outlets each with a 1A capacity. Some smartphones take a full 500mA to charge and that will only get them on the slow charge. Most wall chargers are rated at 700mA or more to get the fast charge. My Sena unit charges at 750mA so the 1A output will be perfect. If it works out, I will design a circuit board to go in a watertight box. I will be testing it the last week in June when my wife and I are going on a trip for a long weekend.

What you have there, is a firestarter......
You are wanting close to 1 amp, with a drop of 7 to 9 volts. Or up to 9 watts each. Those heat sinks you have there are good for maybe 2 watts, so they will do a meltdown with that actual 7 or more watts.
You need a big thick slab of aluminum.

The fast/slow charge of most smartphones is determined by the way the cable is wired. (assuming you use heavy enough wire)

[jmanz6]

I've used the single 7805 before with no issues. I'm not worried. I just want to have both USB ports have the same 1A capability. The one I used before didn't have any heat sink either. I made a charger that had a 500mA regulator and it works great, but my smartphone will switch between charging and not charging when connected. With most other devices (GPS, other phones, etc) it works great. I found with some smartphones, they won't even see the USB power unless the 2 data pins are shorted.

[mouthfulloflake]

I have been using a single 7805 also, they dont get that hot with a small heatsink, and if they do they just shut down for a bit.

Put the heat sink in the air flow ( I zip tie mine to the handlebars)
and you cant even feel that its warm in use.

[jmanz6]

If it does get hot, I will simply design a heat sink to replace the top of the box and mount them to the heat sink. This is the reason for the proto board, this is the first design of this charger, mostly for proof of concept at this point. If it works like I think it will, then I will move on to making the rest of the parts as I need to.

[mouthfulloflake]

I will have to mod mine to short the pins 2-3, I thought it was more complex than that to charge a smart phone.

[uraberg]

My initial perusings led me to believe that one needed about 2.5V on one of the data pins, and 2.8 on the other. Then I found a whole bunch of posts by people who got it to work with just shorting the pins.
Much easier than soldering a voltage divider circuit in, but as I said, I have yet to try it.

Originally Posted by mouthfulloflake

I will have to mod mine to short the pins 2-3, I thought it was more complex than that to charge a smart phone.

[mouthfulloflake]

right, that was what I had read to, please post up when you test it!

Originally Posted by uraberg

My initial perusings led me to believe that one needed about 2.5V on one of the data pins, and 2.8 on the other. Then I found a whole bunch of posts by people who got it to work with just shorting the pins.
Much easier than soldering a voltage divider circuit in, but as I said, I have yet to try it.

[worwig]

Originally Posted by uraberg

My initial perusings led me to believe that one needed about 2.5V on one of the data pins, and 2.8 on the other. Then I found a whole bunch of posts by people who got it to work with just shorting the pins.
Much easier than soldering a voltage divider circuit in, but as I said, I have yet to try it.

I believe that was the older Motorola standard for mini USB. For micro USB, just short D- & D+.

[worwig]

If you are OK with it shutting down constantly at higher rate, no problem.

I have mine on a 3 x 4 x 1/16 inch aluminum plate with the aluminum RAM mount attached and it still gets hot enough to melt the glue I used to seal it against rain.

Course, not much point in worrying about getting a high charge rate if you are OK with it shutting off constantly.

If I was just charging a phone, I guess I wouldn't care. But when I use my smartphone with a bright display and moving maps, it takes some serious current just to keep the battery from going dead, let alone a bit more to actually put a charge in it.

[mouthfulloflake]

then put 2 of the devices in parallel

massive cost increase of $2.50

and 2 amps if its cool, easily 1 amp if it isnt, problem solved.

Or order up a lm323k, it does 3 amps and 5 volts, and costs about the same, it is a T03 mount ( slightly different than the lm7805)

http://cgi.ebay.com/2pcs-LM323K-TO-3...#ht_500wt_1156

Or there is, which is supposedly a tried and true technique for raising current capacity of a regulator ( stolen from another site)

Here is a simple circuit that will give you all the
current you will ever want.
Use a PNP transistor, of sufficient current to meet
your needs, For a cool 2 amps use a TIP-30.
connect the emitter (pin3) to B+. connect the
collector to "load" (pin2). Connect the base to your
7805 regulator IC (pin1 of TIP-30)to (pin1 of 7805).
Connect the output of the regulator(pin3)to collector
of TIP-30 (pin2). Ground the 7805 (pin2). Add .1 caps
to emitter and collector of transistor. Place a 470uf
cap to Collector (pin2) of transistor. This is clean
and cool, with minimum parts.
A schematics would have been better, but hope this
helps.>>

Originally Posted by worwig

If you are OK with it shutting down constantly at higher rate, no problem.

I have mine on a 3 x 4 x 1/16 inch aluminum plate with the aluminum RAM mount attached and it still gets hot enough to melt the glue I used to seal it against rain.

Course, not much point in worrying about getting a high charge rate if you are OK with it shutting off constantly.

If I was just charging a phone, I guess I wouldn't care. But when I use my smartphone with a bright display and moving maps, it takes some serious current just to keep the battery from going dead, let alone a bit more to actually put a charge in it.

[worwig]

Originally Posted by mouthfulloflake

then put 2 of the devices in parallel
...snip...
Or there is, which is supposedly a tried and true technique for raising current capacity of a regulator ( stolen from another site)

Here is a simple circuit that will give you all the
current you will ever want.
Use a PNP transistor, ...snip...

Don't parallel two devices without balance resistors on the output. And this doesn't cure the heat issue.

The PNP transistor trick works, but doesn't fix the HEAT problem. Now, the PNP transistor will simply cook, and it doesn't have the smarts that the 7805 alone has, so it won't shut down when hot. In fact, when it overheats, it is not out of the question for it to turn into a shorted block of silicon and dump +12 into your phone. Risky.

Heat is simply a fact of life with all linear regulators. Live with lower output current or add a large heatsink.

Here is mine, 14 volts in, attached to a fairly decent piece of aluminum, smartphone pulling 650ma., no forced air flow. 160F is pretty toasty, though still in the SOA.

[mouthfulloflake]

Perhaps thats why mine works flawlessly.



I have an actual heatsink, with a dab of thermal paste between it and the IC, and it has airflow ( when the bike is moving)
Ive never even felt it get warm.

[worwig]

Originally Posted by mouthfulloflake

Perhaps thats why mine works flawlessly.



I have an actual heatsink, with a dab of thermal paste between it and the IC, and it has airflow ( when the bike is moving)
Ive never even felt it get warm.

Yes, an actual heatsink are SO much better then aluminum.

Actually I did start out with a small finned heatsink like that, and at the high charge rate the 7805 kept shutting down due to overheating, even in the wind.

[mouthfulloflake]

I think the fact that yours is 160F and mine is cool to the touch says enough.


I have a box of these sitting around if you want one,



http://www.pricebat.ca/Dynatron-K129...nk.p_10103341/

I used them when experimenting with a peltier type 12Vdc cooler.
they conduct lots of heat.

[mouthfulloflake]

I think I will experiment with putting a small 12v bulb in series with the regulator.

if you could get the balance just right, the bulb would change its glowing intensity depending on the 5V load, and drop the input voltage to the regulator somewhat mitigating the heat issue right?

I was thinking of using the pilot or running light inside the headlight housing.

its already there, wiring is easy.

what do you think of that idea?