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Author Topic: Reducing Excess energy consumptiom  (Read 1266 times)
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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
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Its not that clear what you are trying to achieve so it might be best if you posted a circuit diagram.

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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.
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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.jpg (89.21 KB, 1157x499 - viewed 38 times.)
* Board.sch (336.01 KB - downloaded 10 times.)
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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.
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Thank you!

Sorry for the stupid question, but what is the difference between a switching regulator and a voltage regulator?
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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.
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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.
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Manchester (England England)
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There is no waste.
So 100% efficient are they?
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There is no waste.
So 100% efficient are they?

Oh, yeah, yeah.  Right Mikey.

You're a real piece of work.

Troll....troll....
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Manchester (England England)
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Ha so I am a troll for pointing out a mistake in your reply.
The whole world must look like trolls to you.
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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.
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Lacey, Washington, USA
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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.
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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.
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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.
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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. smiley
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