Heatsink em, Run parallel em
This will increase your amps
In an effort to eliminate my inverter completely (laptop setup) I need to power my 2 usb hubs.
One is a Belkin 7 port calling for ~3.5 amps
The other is a no name 4 port calling for ~2.5 amps
I have looked into the 5v POL mp3car sells, but they are WEAK.
I have looked at these two as well:
But, 7805's are so cheap... however they are only rated at 1 amp...
Anyone using them to power a hub or just individual usb devices?
I originally used a couple 7805 to power my usb hub and accessories, but it ended up pumping out a LOT of heat. 7805's are simple, but VERY inefficient. I replaced with the Jopel 5V power supply, and love it. It also doubles as a decent accessory control relay, with the 12V unregulated output. It supplies a MUCH cleaner 5V, provides more than enough current, and even has the nice and convenient USB control signal option. By the time you build a linear regulator using 7805's, board, terminals, proper heat sinks, a decent case, switching relay, fuse, the $80 for the Jopel starts to not look so bad.
2000 Ford Expedition Eddie Bauer - Bi-Fuel Gasoline/CNG
Intel D945GCLF2 w/512MB RAM, CL Audigy w/KxProject, M2-ATX, Lilliput EBY701
as beautiful as the Jopel is, I already have some spare parts lying around...
2 - 7805s, plenty of components (resistors/relays/capacitors/wires), breadboard, heatsinks(an old Vantec set for motherboard w/fan)
So not to be completely cheap, would running lets say 4 - 7805s in parallel achieve my goal? And how much heat would that produce?
To quote something from another website, not mine,....
This SourceAnd finally, you can run several 7805s in parallel. The easiest way to do it is to make the inputs a common connection and the grounds a common connection. But don't connect the outputs directly together. The 7805 don't all regulate at exactly the same voltage and the one that regulates at the highest voltage will do all the work while the others loaf along and you'll don't have solved anything. Instead, put a small-value (e.g., 0.47 ohm, 1-watt) resistor in series with each output and THEN connect the other ends of those resistors in common as your final output. That small value of resistance will allow each regulator to work independently of the others and the current will be shared by all of the regulators fairly equally. The down side of this fix is that it makes the regulation a little bit "softer" (i.e., a higher internal resistance for the supply), but in most cases, won't be much of a problem.
Another page from same site
One more as well
If you do it as dean suggests, then you should be all set.
Also i would get a small metal case and enclose them in it and use it as the heat sink... Think of how the normal car inverter cases are....
I realize this is not an option for most people and is a wasteful method, But if done right can be a cheap and quick alternative in the mean time until a more "Complete" power supply system can be built...
Being realistic in this approach, heat in a vehicle is a factor. But on the other hand, my laptop gets quite warm, amps, laptop power brick, ect....
The 2995 circuit looks nice as its rated 5 amps, HOWEVER...
7805's are readily available at Radioshack, if one was to order something wouldn't it be wiser to order a Jopel? Yes
I am looking for a permanent solution. I'm confident in my handy work building a 7805 system properly sink'ed. How many watts of heat are we talking about for 4-7805s? Pushing a ~6amp load? And would this be a wise/viable permanent solution?
P = U * I = 9.4V * 6A = 56.4W
This is a lot of heat to dissipate. At 6A you need a DC-DC converter, which are > 80% efficient.
Are you really going to pull 0.5A from each USB port? Calculate the real power draw, and then aim for supply for 125% of that value.