darlington pair for circuit

Hello!!!

i have a circuit whose output is 4.7 v and 143 micro Ampere
now i want to drive simple led..

i want to increase current upto 10 mA , what should i do??? can i use darlington pair or else

Thanks !!!

Why do you want to increase the current? A typical led need far less current to lit properly.

Please provide ypur circuit and kind of load to put onto it.

i have a circuit whose output is 4.7 v and 143 micro Ampere

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I'm afraid that alone isn't enough information. The current depends on the load, not just the voltage so you can't use it to characterize a source unless you say "it gives 4.7V when a 143uA load is applied". Looking at the worst case, if you wanted to boost the current from 0.000143A to 0.01A you would have to multiply the voltage by 69.9 times and the voltage would therefore have to be increased to 329V !

If you show your circuit it will help us to understand the reationship between the voltage it produces under different loads.

Brian.

Hello !!!!
Thanks for your kind reply...

can i increase the current via darlington pair or not??

my circuit is below

That is a IR receiver module? The output can be used to drive a transistor and the transistor can be asked to drive a LED. You can use any garden variety (say 2N2222) NPN transistor.

Please don't post 3.1Mb pictures of a simple diagram, please consider those of us who do not always have a fast internet connection. It took me over a minute to download!

Although you stil haven't explained what you are trying to do, I'm guessing you want to flash an LED when an IR code is received but the IR receiver can not produce sufficient current. If I'm right, all you have to do is use a single NPN transistor. Connect R1 to it's base instead of the LED. Connect it's emitter to GND (the negative side of your supply) and move the LED so it is wired between +5V and the collector of the transistor. Important: add a 330 Ohm resistor in series with the LED and orientate the LED so it's cathode end is toward the transistor.

I think the SM0038 is one of the less reliable IR receivers, there have been problems reported about them. Also beware that the output is only the data pulses themselves from the IR code, you will not get one flash but a sequence of very short ones, each lasting only a few mS.

Brian.

Prototyp_V1.0 said:

... A typical led need far less current to lit properly..

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Most common LED need 5-20 mA of current for a reasonable output. Your statement above is not accurate.

I copied your schematic which you saved and posted as a HUGE BMP file type and used a clear but small PNG file type instead.
The SM0038 is a copy (maybe a poor copy) of a standard TSOP1738 IR receiver IC that has its output go LOW (not high) when it detects bursts of IR at 38kHz.
It can drive an ordinary little PNP transistor through a 2.2k resistor and the transistor can drive a 20mA red LED through a 160 ohms resistor like this:

Dear audioguru
I have do as per your schematic
But my led blinks continuesly even I didn't use remote
What should I do?

Hello
can i drive relay using Relay using same circuit ???

hirenn said:

Dear audioguru
I have do as per your schematic
But my led blinks continuesly even I didn't use remote
What should I do?

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I think you should throw away the lousy SM0038 and use a real genuine TSOP1738. But the TSOP1738 is not made anymore.

can i drive relay using Relay using same circuit ???

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Certainly; but it may produce only chatter and perhaps may not even respond because the pulses are quite fast...

Use a reverse diode parallel to the relay coil as a safety feature.

Hello audioguru
I get new sm0038 and I make again as per your circuit and working great...
Will you please tell me how can I drive 5v relay using same circuit
Thanks

You need to learn to decode; read the sequence of pulses and identify it with a particular key press on the remote. Keyboards are multiplexed and that makes your job simpler.

hirenn said:

Hello audioguru
I get new sm0038 and I make again as per your circuit and working great...

Click to expand...

Goody.

Will you please tell me how can I drive 5v relay using same circuit.

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A relay coil has a rated current that might be 10mA or might be 5A. Then the transistor circuit must match it.
A relay is mechanical and might not work with fast IR pulses. What will your relay drive?