Hello there. I recently solved an issue with my breadboarded ATmega328s acting strangely because of an overheating voltage regulator. (I was trying to turn a servo motor very often) I had this problem because I was using a 12V regulated adapter. I know that another solution would be to use a 9V adapter instead, but I have plenty of 12V adapters that I would like to make use of.
I noticed that when I ran my motor turning sketch on the actual Duemilanove, it would run flawlessly and not overheat. Would it be possible to get a TO-220 version of that regulator? And maybe some 47uf capacitors and a nice breadboarded barrel jack as well?
First: One should take - as you now already know - a little bit more care with voltage regulators...
Alas, in the hobby area the commen answer is still: 7805. However this is a monster leftover from the late 20th century, like the 741 opamp and the 555. Don't touch them, if you can avoid it. They are - well - antediluvian...
The modern approach to voltage regulation is "switching" (buck or boost mode), the problem of which seems to be that you need a small coil as a supporting part to the regulator rather than the 4 classical ingredients to make the 7805 work (2x 47uF, 1x 10 nF, 1x4001 from output to input). And - admitted - it will be close to $1 from the other side of the dollar...
If you have to use a linear regulator, than take a so called "low drop regulator" or even a "very low drop (down) regulator". Their advantage is not only that you can provide 6V only to them, but that they are much more parsimonious with there own part of the current....
However what you noticed had most likely to to with a better heat sinking on the Arduino board. Though not very noticeable, it has a good thermal contact. It is not really enough to let a TO-220 chip just stand up hoping for the next stiff breeze...
You probably just need a heat sink on your regulator.
However, the one used in the latest Arduino is a MC33269, which is available in a TO-220 package. This was found by looking at the Arduino 2009 schematic and then using Google.
This regulator in a TO-222 will likely need a heat sink as well.
Alas, in the hobby area the commen answer is still: 7805. However this is a monster leftover from the late 20th century, like the 741 opamp and the 555. Don't touch them, if you can avoid it. They are - well - antediluvian...
Hey! I resemble that remark...
The modern approach to voltage regulation is "switching" (buck or boost mode), the problem of which seems to be that you need a small coil as a supporting part to the regulator rather than the 4 classical ingredients to make the 7805 work (2x 47uF, 1x 10 nF, 1x4001 from output to input). And - admitted - it will be close to $1 from the other side of the dollar...
Yeah - the coil is the tougher part of the equation; there are a couple of companies out there, though, that make a switching regulator 7805 (and other size) work-alike, in a very similar form-factor (a little thicker due to the coil, I believe). They include all the components, and are very close to a "drop-in" replacement. They are, however, a bit pricey (around $15.00 US)...
It sounds like I am either going to have to buy a 25 cent heatsink or a $3 9V regulated adapter. However wherever I go I cannot seem to find a place where I can get reasonable shipping. AllElectronics wants $7 to ship heatsinks that cost $1 combined. No.
It sounds like I am either going to have to buy a 25 cent heatsink or a $3 9V regulated adapter. However wherever I go I cannot seem to find a place where I can get reasonable shipping. AllElectronics wants $7 to ship heatsinks that cost $1 combined. No.
If you're buying something online, certainly there are more parts or other junk you could put in to the order before that $7 shipping goes up. Call up All Electronics and ask them what other kinds of things you could put into the order before the shipping increases (you should be able to put something in there that costs more than $7, so at least you would "break even" so-to-speak)...
You could always build your own heat sink, too; get a small copper coupling (from a hardware store), hacksaw it lengthwise, pound it out flat, cut it down with some tin-snips, drill a hole and bolt it on.
Alas, in the hobby area the commen answer is still: 7805. However this is a monster leftover from the late 20th century, like the 741 opamp and the 555. Don't touch them, if you can avoid it.
I disagree: The 7805 is common, cheap, well-known, and easy to use correctly. If you can tolerate the inefficiency (and IMO you can, if you're running off a wall-wart) it's a good choice.
Switchers are more efficient, but they are also noisy, require more components, usually picky about the types and values of the supporting components required, and generally more difficult to use correctly than a 7805.
If you've got a scrap chunk of aluminum (maybe flat or angle stock left over from some project, or a small piece of sheet Al), that's good enough as a heat sink.
I bought one of these bad boys for improved efficiency over the 7805 for a custom setup for a robot I'm makin as soon as I get the rest of my parts. It worked with as low as 5.3 volts (4 rechargeable AA batteries) output 4.98V. I'm happy with the purchase.
with as low as 5.3 volts (4 rechargeable AA batteries) output 4.98V.
But you give him' no real chance ;D Its just that you reduce the voltage during the short time of overvoltage until the batteries soon (!) drop down to their nominal value of 4.8 volts....
For this special case a Schottky diode will virtually do the same.
I should propose to use the adjustable version an wire it to 4.6 volts or such. Or just leave it without any regulation at all...
But you give him' no real chance Its just that you reduce the voltage during the short time of overvoltage until the batteries soon (!) drop down to their nominal value of 4.8 volts....
;D Fair.. haha just an example of the Low Drop Out that doesn't seem to be mentioned on the product pages.. but I guess that's not really an issue here!
Umm, will this efficiently reduce 12V to 5?
The regulator will accept up to 40 volts at 1 amp continuously. (You'll need a heat sink at 40 volts, but with the high efficiency, heat sink isn't required for lower voltages)
So yeah, it will. The one thing I'd be worried about is your current drain. (and the amount the power supply you're using supplies) Servos can take up to a few hundred milliamp's with no load, higher with a load.. and that's assuming they're not the "extra powerful" version.
I've got micro servos that run about 250ma each (stalled) , only using 2 and the Arduino so I'm a fair margin below 1amp. (it is protected with thermal shutdown and over-current protection, just in case;D)
[edit]I just re-read the first reply by deSilva.. lol, he already linked to a version of this regulator, guess consider this an advertisement for Gravitech:D (great Seller by the way)[/edit]
The 2575 is popular because it is extremely easy to wire. There is only a coil of around 330uH needed (mind the current rating!) .
This coil often gives cause for discussions... It is not essential, it is part - together with a cap - of a most classical 2. order low pass filter to suppress the already mentioned high frequency which is the primary output of the chip. Any RC filter will do the same though not so efficiently...
Though there are also adjustable versions of the 2575 it is easy by adding some diodes at the FB pin to increase the output voltage of fixed types in 0.6 volt steps (5.6, 6.2) if needed.
When inputting 25V or even 40V mind the rating of the buffering input cap, electrolytes should be considerable higher than the nominal voltage. If you use a smooth power supply anyway, it is better to reduce this cap's capacitance rather than take a marginal voltage rating....
Another interesting feature is that it can digitally be switched on and off!
