So this has been an amazing community for figuring out my questions so far, and well here's another! Now, I know voltage is present everywhere in your circuit (just in general). If you have 3 light bulbs in a simplistic circuit they are all drawing the same voltage. Now with amperage I have an understanding of "the load takes what it needs and leaves the rest". So if im running 12v at 10amp through a 1amp voltage regulator down to 9v and my load runs at 9v below 500ma does that mean that only 500ma is running through the regulator (this it's fine and I won't smell any magic smoke) or will the voltage regulator fry because even though the load is only drawing 500ma the current is still going through the voltage regulator? Let me know if you guys need any further clarification.

 

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if im running 12v at 10amp through a 1amp voltage regulator down to 9v and my load runs at 9v below 500ma does that mean that only 500ma is running through the regulator (this it's fine and I won't smell any magic smoke) or will the voltage regulator fry because even though the load is only drawing 500ma the current is still going through the voltage regulator?

If you are referring to a linear regulator, then the input current is basically the same as the output current.
So 500mA output means 500mA in.

1 amp is just the regulator maximum rating.

Is 10A the rating of the 12V supply?
That has nothing to do with the current going through the regulator.

 

Thanks for the quick response! My linear regulator shouldn't blow up then

 

Right, there is almost no current consumed by the regulator itself, in excess of the load current. But the load current does drop in voltage in the regulator, releasing heat that must get dissipated.

 

Does this regulator need a heatsink? Did it come with one already attached?

 

Does this regulator need a heatsink? Did it come with one already attached?

Well it didn't come with a heat sync so I dremeled out a thickness of copper sheet and they work pretty well. Anyhow I ended up frying 1 of the voltage regulators trying to test it with no sleep (by having a 5ohm 10w resistor as the output load). I'm pretty sure it'll work out fine if there's an actual 500ma load converting 12v down to 9v. Not sure if voltage regulators only regulate from high to lower or if I can feed this thing 7v and it will regulate up to 9v..

 

...or if I can feed this thing 7v and it will regulate up to 9v..

No, linear regulators can only act like a smart resistor to reduce voltage, never increase it. For that you need a switching regulator called a boost regulator (buck regulators reduce voltage). These are the modern approach since because they are far more efficient and don't need to dissipate so much heat.

 

No, linear regulators can only act like a smart resistor to reduce voltage, never increase it. For that you need a switching regulator called a boost regulator (buck regulators reduce voltage). These are the modern approach since because they are far more efficient and don't need to dissipate so much heat.

Thats what I had thought, just confirming. So let me ask a couple more questions so I don't blow up something..
A. Would giving it a lower current than it's designed to operate at cause some magic smoke or would not much happen?

B. Is there a easy way to limit/protect too much current from being pulled through the regulator?

 

You had said earlier that you had 12 V and a regulator to a 9V Load that drew 0.5A.

That means the regulator has to dissipate (12-9)*0.5 Watts. So, about 1.5 W which isn't a lot. There are ways to figure out what size heat sink you need. The LM317 series drops the voltage to 1.2V when overloaded. Overvoltage input transients tend to kill regulators. The LM317 needs a 3 V differential to work reliably. So, that stuff is in the datasheet.

A. If your within the limits of the regulator your OK. So, you might have a 1.5 A regulator that needs a 10 mA minimum load, anything between 1.5A and 10 mA is fair game. The set resistors should draw the minimum load, People make mistakes here.

B. Generally the regulator is smart up to what it can do. If the power dissipation is exceeded all bets are off. So, in the case of the LM317, the regualtor has to be able to handle 1.5 A and 1.2 V indefinately for a short circuit and (Vin-3-1.2)*1.5 Watts must be safely dissipated.
Vin is the unregulated voltage; 3 is the estimated drop across the regulator; 1.2 is the output and 1.5 A is the max current.

This is "first order" type of answer using a common linear regulator that you did not mention. It may or may not be the right answer for all regulators or power supplies.

 

Thats what I had thought, just confirming. So let me ask a couple more questions so I don't blow up something..
A. Would giving it a lower current than it's designed to operate at cause some magic smoke or would not much happen?

B. Is there a easy way to limit/protect too much current from being pulled through the regulator?

Check the datasheet on a typical 3-terminal linear voltage regulator such as LM7805 or LM317.

You will find:

• Internal short-circuit current limiting
• Internal thermal-overload protection

That is, you can safely short circuit the output to ground.
If the device overheats it will shut down.
Practically break proof. Almost. I have had to replace linear voltage regulators for one reason or another.

 

Thats what I had thought, just confirming. So let me ask a couple more questions so I don't blow up something..
A. Would giving it a lower current than it's designed to operate at cause some magic smoke or would not much happen?

B. Is there a easy way to limit/protect too much current from being pulled through the regulator?

A. If the load wants say, 1A at the target voltage, you could only starve it for current by lowering the voltage to the regulator so much that it can no longer output the target voltage. That would not harm the regulator.
B. The best way is to avoid overloading it. You can also use a fuse on either side of the regulator.