Voltage regulator--how to mount?

[JBotAlan]

Hey,

I'm using a RadioShack voltage regulator to regulate 5v for a project I'm working on. I have this regulator:
http://www.radioshack.com/sm-5v-fixe...i-2062599.html
and I'm trying to figure out how to mount it. What is the safest way to mount such a regulator?

I'm aware that it will get hot if it steps down voltage (which it will have to in my project), and so that rules out hot glue or any other thermally-insulating glue. I'm mounting it to the inside of an Altoids tin, so I figure I should use the tin as a heatsink--but I'm a programmer/electrical guy and have no idea what my options are.

Thanks for your input,
JBot

[tseres]

epoxy? i'm not sure....or else you could use "the last glue" www.thelastglue.com . this stuff is awesome for everything. i have it, and it is perfect. it honestly glues everything (except food grade polypropelene or cotton).

[whytheheckme]

Are you using a breadboard or just a board with holes in it? Either way, you can simply bolt the heatsync to it and have it stand straight up, like this

[PoorASCIart]

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[/PoorASCIart]

If that made sense. I can try to find pics.


EDIT... Just read your post... properly... I guess you could drill a hole in the tin and use the bolt hole for what it's intended (a bolt), and simply secure it this way. You may have a problem with the contacts touching though... not sure of exactly how it looks.


Jacob

[jgannon]

Radioshack sells two different things that are meant to go with TO-220 package semiconductors (which is what your regulator is).

Here is some mounting hardware and insulation:
http://www.radioshack.com/product/in...2230.203 2272

Here is a heatsink:
http://www.radioshack.com/product/in...2230.203 2272

Which route you want to take depends on your space limitations, your mounting medium, and how much heat you expect to be generating.

[Adam Shapiro]

What voltage are you regulating from and what load are you using the regulator with? Low-dropout regulators can get hot, but as long as you're not putting too much strain on them and they have enough air circulation you can possibly get away without a heatsink at all which makes mounting a great deal easier. If you're not stepping down the voltage too much and the load is sufficiently low you may not be drawing too much power through the regulator. Be careful though, the regulator will still get hot and could burn you if you're not cautious. As for mounting, the regulator has a standard TO-220 package so the legs are .1 inches apart. You can simply place it on a protoboard of some sort (also available at RadioShack) and wire to it as necessary.

Edit: Joey beat me to it.

[Al Skierkiewicz]

Jbot,
The 7805 series regulators have the center pin and the tab at the same potential, i.e. power supply common. It the Altoids can is going to be grounded, you can just bolt the tab directly to the can. A little heatsink goop will help in the tranfer. The way this works is a simple calculation on the drop and current for the regulator. If you are dropping 4 volts (9 volts in to 5 volts out) at 100 ma you are going to have .4 watts dissipated by the regulator. Not too bad. If you are dropping 7 volts (12 in and 5 out)at 1 amp then you have to get rid of 7 watts and that will cause you some problems with just the little can to get rid of the heat. You can always add a good heatsink to the bolt on the outside of the can to increase the amount of heat you can transfer to the air outside of the can. That way both the can and the heatsink will dissipate the heat. Remember that this family of regulators does have temperature compensation that will lower the output if they start to run hot.

[DonRotolo]

What Al ^^ said.

Also: The hole is what you use to fasten these things to heat sinks and altoids cases. Nobody uses adhesives.

Use a small (#6) nut and bolt to fasten it. White heat sink goop will help a lot. An altoids tin is probably good for 1.5 or 2 watts, max, assuming free airflow. whytheheckme's suggestion to bolt a heat sink to the outside is a good one, with heat sinks, bigger is always better.

Put some tape under the metal leads coming out of the regulator so even if bent a bit they won't short to the case.

Don

[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