Voltage regulator--how to mount?

[JBotAlan]

Thanks for the input.

I might as well say what this is for...I'm planning on copying someone else's idea, wiring up the 5v from the regulator to a USB port. That way I can charge my iPod and at least power (not necessarily charge, due to some slightly more complex circuitry in the charger) my Motorola Razr on the road from a 9v battery (or 2). I don't honestly know what the draw is like to charge/power either device. I suppose I should do my homework before I tinker around any more...or I could do it by trial and error.

The more practical/serious use for this is stepping the 12v on the robot to 5v for my custom camera board. Again, I have no ideas as to how much this draws. I can pull out the meter and measure it, if need be.

Thanks (for taking me seriously after I said flat-out that I was mounting something in an Altoids tin...)

JBot

EDIT: [offtopic] Al, did you guys get your faulty pot wiring figured out yet? It looked like someone had cannibalized those PWM y-cables for pot wiring--every single one of those I've used has turned out defective, so I don't use them anymore. Had you seen that before Atlanta? And was that the problem you were having at Atl?[/offtopic]

Sorry if I seem a bit incoherent/rambling...I really should get some sleep. And yet I continue to type...

[Stuart]

you know Ive used the 7805 for lots of projects(usb car charger, loads of ttl circuits off of 9/6v), and Ive never had a problem with over heating(not to say it doesn't get hot just that it doesn't seam to be a problem). so you can put a heat sync on it if you'd like but I think that may be over complicating things.

[karlcswanson]

if it is for charging a USB device it should not pull more than 500 ma. I made one of these devices a while ago and just soldered a 9V battery snap to the input side of the LM7805 and a usb connector on the output side and wrapped it all in a blob of electrical tape after bolting the LM7805 to a piece of metal. It worked. Since than more efficient designs have been released on to the internet such as the MintyBoost

[Adam Shapiro]

Originally Posted by JBotAlan

The more practical/serious use for this is stepping the 12v on the robot to 5v for my custom camera board. Again, I have no ideas as to how much this draws. I can pull out the meter and measure it, if need be.

Regulating 12V to 5V with that regulator and an unknown load might produce a good deal of heat. For that case you're going to want to have a good heat sink at least. Is it not possible to power it off the RC directly? If you're worried about it you could use a switching regulator for the same purpose. They're much more efficient and shouldn't get very hot at all.

Originally Posted by JBotAlan

Thanks (for taking me seriously after I said flat-out that I was mounting something in an Altoids tin...)

I actually had a friend who made an iPod charger out of an Altoids tin a number of years back. It worked pretty well, and always smelled curiously strong.

[MrForbes]

remember when ipods used to come with chargers? the one my wife got a couple years ago did, at least.

the charger has a jack for the firewire cable. the charger is rated 13 vDC at .62 amps

in case anyone was curious.

anyways, a chunk of sheet aluminum makes a dandy heatsink to put on a 7805 if needed.

[JBotAlan]

Originally Posted by Adam Shapiro

Is it not possible to power it off the RC directly?

I believe because of poor wording that this is not legal under the 2007 rules. However, this is irrelevent (until next year, anyhow) because there is no tech inspection at IRI...I'll just make sure I insulate it well.

I will measure the load of that camera board, possibly tonight, to see if it is going to work for my purposes.

And I'll probably go through with that curiously strong charger. I'm taking a look at MintyBoost to see what I can borrow (steal) from there.

JBot

[John Gutmann]

You can hot glue it.

Now before any body jumps at me, if it gets hot enough to melt the hotglue he has bigger problems then how he is mounting it. I have use a 7805 to regulate down form 9 volts to run a servo that had a big load on it. The regulator got now where nere hot. It got "warm" if you can call it that. it was barely enough for me to feel.

-John

[Dave Flowerday]

Originally Posted by JBotAlan

I believe because of poor wording that this is not legal under the 2007 rules.

It was legal in 2007:
http://forums.usfirst.org/showthread.php?t=1518

[JBotAlan]

Originally Posted by Dave Flowerday

It was legal in 2007:
http://forums.usfirst.org/showthread.php?t=1518

Oh, I know that I had a discussion for awhile during the season here on CD, but I didn't know there had been an official response. Thanks for the link.

JBot

[ntroup]

Originally Posted by JBotAlan

[offtopic] Al, did you guys get your faulty pot wiring figured out yet? It looked like someone had cannibalized those PWM y-cables for pot wiring--every single one of those I've used has turned out defective, so I don't use them anymore. Had you seen that before Atlanta? And was that the problem you were having at Atl?[/offtopic]

Not to de-rail this topic again too much, but I wanted to add an update. After further investigation, the wiring was not at fault at all. We do not use 'cannibalized PWM y-cables', but actually create our own out of bulk PWM wire. The wiring was stressed a bit, but not defective or faulty. The digital pots, however, were where the problem was. Both the elbow and the shoulder pots are the MA2s from usdigital.com, and both died, either due to static shock or strong magnetic field too near them (as they work off change in magnetic fields to determine rotation). We are still investigating the root cause.

Either way, we are fixed, and ready to rumble at IRI now

-Nate