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Topic: MOSFET help (Read 1 time) previous topic - next topic

lRaHl

I have 6 IR LEDs that I want to run off a cigarette lighter outlet in a car. (High output infrared LED 5mm 1.2VDC 100mA 940nm)

Currently I have all six in series with a 100ohm 1w 5% resistor.

I want to have them blink using a IFR510 MOSFET could someone provide me with a schematic?

billy_welsh

#1
May 20, 2011, 04:06 am Last Edit: May 20, 2011, 04:23 am by billy_welsh Reason: 1
I think this can help you.

http://www.youtube.com/watch?v=Te5YYVZiOKs

What do you want to use as a timer?

You could use a 555 timer if you just want it to blink.

http://en.wikipedia.org/wiki/555_timer_IC

lRaHl

I am going to use the Arduino Uno as the timer. Pin 2.

My 6 leds are in the place of "M". But for some reason this is not working for me.

The leds are sometimes off, blink at the inncorrect freq, or just stay lit.



Code: [Select]
int led = 2;

void setup() {
  pinMode(led, OUTPUT);     
}
void loop() {
  digitalWrite(led, HIGH);
  delay(35);
  delayMicroseconds(544);
  digitalWrite(led, LOW);
  delay(35);
  delayMicroseconds(552);
}

billy_welsh

I have a feeling your code is operate so fast that you can't see it. Try commenting out the microseconds and bringing delay up to a second to see if it starts to blink with more repetition.

delay (1000);

qwerty156

I am also creating a similar project but would a IRF540 work instead?
Would i need a resistor between the arduino's digital pin and the transistor?

AWOL

Quote
I have a feeling your code is operate so fast that you can't see it.

They're IR didodes - unless it is very dark, you proabably won't see them anyway, though if were visible LEDs, you'd probably see the flicker.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

MarkT

IR diodes produce absolutely no visible light - but digital cameras (unless they have a really good IR filter) can usually see them - phone cameras are most likely to lack an IR filter.

The IRF510 is not a logic level MOSFET and won't work properly from 5V gate drive.  You must use a logic-level MOSFET or level-shift the pin's output to 10 to 12V.
[ I won't respond to messages, use the forum please ]

AWOL

Quote
IR diodes produce absolutely no visible light

No so - it is possible sometimes to see a faint glow from bare (without a proper filter) IR illuminators, though I agree, digital cameras are usually a good bet, and 940nm is quite a long wavelength
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

billy_welsh


They're IR didodes - unless it is very dark, you proabably won't see them anyway, though if were visible LEDs, you'd probably see the flicker.


I was half asleep thanks for pointing that out.

Do the UNO boards still have the LED on pin 13. If they do you could probably trouble shoot the timing just by adding pin 13 to the rotation.

MarkT

Standard IR diodes are ( or used to be ) narrowband and dont spill into visible. Perhaps newer high efficiency ones use quantum wells and produce a broader spectrum? IR remote control wants narrowband emitters and receivers to help filter out ambient lighting which interferes with wanted signal - IR illuminators just need high efficiency.
[ I won't respond to messages, use the forum please ]

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