# Reducing Excess energy consumptiom

Hello,

I am trying to create a circuit that will run of 13.5v, with an on off switch. I would like to have an LED light up when it is plugged in. I was planning to use a 600 ohm resistor connected to the led in a parralel circuit with the switch and the rest of the components. It occured to me that this would resolt in major excess heat and energy loss, even when the device it turned of.

Is there a way to reuse stored energy, such as a capacitator?

Thanks you,

Sasha

Its not that clear what you are trying to achieve so it might be best if you posted a circuit diagram.

I was planning to use a 600 ohm resistor connected to the led in a parralel circuit with the switch and the rest of the components.

If its in parallel to the switch it will only come on when the switch is off and will provide limited current to the rest of the circuit even when the switch is off.

Connect the series resistor/LED combo across the input of the circuit/device you are driving (i.e. in parallel)and the LED will only light when you turn the switch (and the circuit) on. No power will be used when the switch is off.

Sorry, I may not have structured my question correctly. I have attached a schematic and an image of it to this post. The LED that I am referring to is called LED Standby

Board.sch (336 KB)

That LED is going to be on all the time, even when the switch is on. I would not say the heat would be excessive. You can always make the resistor much bigger and use an efficient LED. A while LED can run on only 1mA that would mean something like a 10K resistor. The other choice is a switching regulator which is a bit more effecent than a resistor here.

Thank you!

Sorry for the stupid question, but what is the difference between a switching regulator and a voltage regulator?

The way it works. A voltage regulator burns off excess power as heat. A switching regulator puts energy into a coil and extracts it with the voltage you want. The only loss is due to absorption in the coil's core.

Sasha831: Thank you!

Sorry for the stupid question, but what is the difference between a switching regulator and a voltage regulator?

Voltage regulators come in two types. Switching regulators and linear regulators.

Switching regulators regulate the voltage by turning on and off the supply very quickly to keep their output voltage at a steady value. In effect, they only let through what is needed by the load. There is no waste.

Linear regulators regulate the voltage by using a dynamically variable voltage drop, usually across a transistor, to keep the output voltage constant. This results in excess energy being dissipated as waste heat.

There is no waste.

So 100% efficient are they?

Grumpy_Mike:

There is no waste.

So 100% efficient are they?

Oh, yeah, yeah. Right Mikey.

You're a real piece of work.

Troll....troll....

Ha so I am a troll for pointing out a mistake in your reply. The whole world must look like trolls to you.

There is no mistake in my reply. I was not talking about 'cost', but 'waste'. There is no waste in a switching regulator. Yes, of course there is a cost. There is a cost to everything.

So here, let me give you another analogy, and include all the little details so that I don't leave anyone behind.

Scenario: You are away on a work mission. You get paid \$15 a week and need to send \$9 a week back home.

Option 1: You can go to Larry Linear's service. He'll take your \$15 check, keep \$1 for himself (the cost, not wasted. Larry needs this to do his job), forward on the \$9 and throw \$5 in the trash. There is \$5 waste.

Option 2: You can go to Sam Switching's service. He'll take your \$15 check, keep \$1 for himself (again, the cost, not waste) forward on the \$9 and give you back \$5. There is no waste.

The moral of the story is, neither one is 100% efficient, but one there is waste, the other there is not.

Grumpy_Mike: The way it works. A voltage regulator burns off excess power as heat. A switching regulator puts energy into a coil and extracts it with the voltage you want. The only loss is due to absorption in the coil's core.

And I2R losses, and the power required to run the SMPS circuits, and RF radiation losses... In any case, with a 20mA current through an LED, it would take some careful IC selection and circuit design to make that appreciably more efficient.

Much simpler, IMO, would be to have the LED blink to indicate the presence of power. A short blink every second would be sufficient to let you know it is plugged in, but with a short duty cycle, save that power.

polymorph: Much simpler, IMO, would be to have the LED blink to indicate the presence of power. A short blink every second would be sufficient to let you know it is plugged in, but with a short duty cycle, save that power.

Good, simple idea.

Get some perspective. From the point of view of the payer there is no difference between cost and waste. What you call waste is just the cost of using a linear regulator. At the end of the day all ends up as heat.

Sure Mike. I'll look at everything your way. Your perspective is the right one. No one else matters. Glad to have you to show me the light so just PM a full list of your 'perspectives' on things and I'll do my best to be just like you. :)

Grumpy_Mike:
Get some perspective.

Are you just going to jump all over everything BillO writes? How does this inane arguing help the OP? If another user shares something you might not agree with, it’s enough for you to share your ‘perspective’ for the rest to see without the personal attacks.

There is usually more than one way to skin every cat and the OP is best served by seeing as many of them as possible, not by seeing endless dribble about why you think some other response is not to your liking.

DirtBiker: There is usually more than one way to skin every cat and the OP is best served by seeing as many of them as possible, not by seeing endless dribble about why you think some other response is not to your liking.

It is starting to seem like a personal vendetta.

It is starting to seem like a personal vendetta.

Nothing personal. But if some one says something here that is wrong he is open for correction. That applies to me or any one else. The fact that he keeps producing spurious arguments to try and justify what he said originally was right by playing semantics is his own choice. A simple:- "I didn't meant to imply that the conversion was 100% efficient" would have been all that it needed, but no he has to argue.

This thread is a perfect example of some one getting something wrong and learning from his mistakes not arguing that he was right all the time. http://forum.arduino.cc/index.php?topic=176167.0

In all fairness, I do not think I said anything wrong. I did not say everything I should have in order to explain myself, but that does not make it wrong, just incomplete, and yes, that is my fault. I am not an engineer, and I think that may be part of the issue. My background is experimental physics so I may look at things from a different perspective than those that are trained engineers and technologists. I often forget that those with more rigorous technical training are used to, and expect, more precise descriptions.

This is not offered to be an excuse, because I am aware of the audience here and it would be my responsibility to ensure the completeness of my responses, especially if they go against accepted dogma in some way. However, most of the physicists I know (including myself) are masters of the “hand waving” argument. This is where we tend to assume a lot, because we all know it’s there, so it’s waived aside to talk about the matter at hand. In support of that behavior, if we did not we would be mired down in endless minutia about the basic laws of the universe in every discussion we have. So generally we’ll not discuss the application of, for instance, the laws of thermodynamics every time we discuss an event where there is an energy exchange.

Sometimes it is very enticing to just skip the explanations. Yes, I know it’s wrong, but for instance, it seems daunting to try to explain a thing like the difference between the terms cost, loss and waste and how they relate to how a regulators work when the listener is not even aware of what types of regulators there are and how they work, etc…

Just so you know, and again please do not see this as an excuse, as I have already claimed my mistake and responsibility, but just by way of introducing you to where I come form, I look at the total loss of a system as having at least two components such that:

Loss = Cost + Waste

1. Where cost is that component of loss that cannot be eliminated and is a necessary expenditure of energy to perform whatever function is being performed.

2. And where waste is that component of loss that provides no benefit but must be accounted for or targeted to be eliminated.

So, you are right. I should have said “less loss”, rather than “no waste”. But if I had said that to another experimental physicist, he’d want to a full disclosure of the losses to see what could be eliminated as waste and what was absolutely necessary to sustain and I’d be accused of not doing my homework. “losses? What/which losses? Let’s see what we’re talking about here!”

None of us are perfect. I'd rather be corrected than be wrong.

I think all the OP cares about is reducing power used to light the LED without going to great lengths to do so.