Quick schematic check

Hi all i’m designing a cirquit that has to trasmit an IR code with some high power led, i’ve choosen the Vishay TSFF5210 and i’m using 13 ofthem and i drive it with a 2N2222 transistor, can somebody have a quick check if my cirquit is ok or if there is something wrong ? i should archive about 400mA on the led (this should be safe up to 1A with pulses).

I would really apreciate.

Beacon_transmitter.sch.pdf (24.9 KB)

Sorry it will not work. You have the LEDs in the emitter, they need to be, along with the resistor in the collector. Also running high power LEDs with just a resistor limiting the current is a bad idea, you need a constant current supply.

The leds are pulsed since they have to send a code (like a long distance remote) i don’t think i need a constant current cirquit.
i will not have any current flow ?

Those IR LEDs have a Vf max (working voltage) of 1.8volt@100mA.
Your diagram with emitter followers will work in this case, but is inefficient.

As Grumpy_Mike already has explained, the LEDs should go in the collector line.

Then you can have five LEDs in series (Vf = <=9volt) on a 12volt regulated power supply.
That also reduces the size of the power supply, or adds the possibility to use more LEDs.

2N2222 emitter to ground, ~470ohm resistor between Arduino pin and base, and a string of five LEDs with a 22ohm resistor between V-in (your drawing) and collector.
You can use up to four of these circuits on one Arduino pin.

Post a new diagram.

connect leds to the collector.and use resistor to reduce volage

I’ve redone the cirquit with a channel mosfet, i hope this is working better

Beacon_transmitter.sch.pdf (26.9 KB)

Or something like this

Beacon_transmitter_2n2222.sch.pdf (24.6 KB)

Use one resistor for each transistor, with 1 for all you don't have enough current.

Ciao, Ale.

riodda: I've redone the cirquit with a channel mosfet, i hope this is working better

Why are you not using just one MOSFET? The BSS138 is a hopeless choice, it cannot carry high currents.

You claim your LEDs (TSFF5210) are able to handle 400mA, but they are rated at 200mA peak (50% duty cycle), you have 2 LEDs in series from 12V (each LED is about 1.5V, so that's 9V wasted across the resistor - use strings of 6 LEDs, not 2 (assuming the 12V is definitely 12V).

Choose a logic-level MOSFET with a low on-resistance (0.03 ohms or less).

Thanks, actually sending ir codes i think the duty cycle is lower than 50% and i think that in burst the led can handle even more than 400ma.

i think the duty cycle is lower than 50%

Not quite. During the transmission of a logic one the duty cycle is exactly 50%. However you do not always transmit ones.

Why D1? It is doing nothing and if you run the LEDs at anything above 0.25A then you are going to burn it out.

If you want very long-range IR the simplest approach is to use a lens at each end. Throwing many watts of power isn't that efficient.

If you want high power IR, then this is the sort of LED you might want: http://www.ebay.co.uk/itm/10W-20W-30W-50W-100W-730NM-850NM-940NM-Infrared-IR-High-Power-LED-Light-Lamp-/152018762605?var=&hash=item2365063b6d:m:mGrYniZ9syF0nYLHONgdsNg

OP is using IR LEDs with a small opening angle of 10 degrees. Don't know why yet. Long throw remote?

Strings of two LEDs with a 15ohm resistor and a mosfet on an 11.3volt supply (the 1N4004 drops 0.7volt) would be ~500mA through the LEDs. Three LEDs, a transistor, and 20ohm would be ~275mA. Both are not wise.

A single 2N2222 with 150ohm base resistor could drive three strings of five with a 22ohm resistor in each string. Peak current will probably be around 150mA per string, pushing the IR LEDs and transistor to the max. Three strings of four, with 33ohm resistors could also work. Six in a string could be a problem with the 1N4004 in the circuit. Leo..

The criquit is a timing beacon a device used in racecars to take laptimes, in the vehicle there is a receiver that when passes infront of the tramistter triggers a stopwatch.
This cirquit i’m working on it’s a modulated ir beam that transmit a code at 37.9 khz, it has to be narrow becouse it has to trigger the recever also in the same place.
About the led i was considering the bigh ir leds with a lens but i was afraid they will not pulse properly at 37.9khz.
The one i’ve choosen are the most powerfoul/narrow i found on digikey but i’m sure there are alternatives, i know that with pulsed it this leds can be pushed way over their limits.
Regarding the cirquit a did a little of home work a i tryed to do a simulation of the cirquit with ni multisim live, i’ve used one resistor at each transistor to be sure that the current getting to each transistor is the same and i’ve corrected the value of the resistor to stay in the limit of an arduino pwm pin.
With this i get 317mA on each of the 4 string with 21.8 mA out of the arduino pin.
I’ve noticed that on the of phase the current in the pwm pin was becoming negative therfore i put a diode but i don’t know if is needed or not.

Do you mean a beam break sensor. What is the distance you have to bridge. I have succesfully used a SFH400 LED and a PNA4602 receiver to bridge 5meters in bright daylight with only 30mA peak LED current. Without optics. That IR LED can do much more than that. You might be overthinking it with that many LEDs. Do some tests.

A diode is lowering base current. Remove it.

This sketch can be used to generate a constant 38kHz signal for the IR LED(s). Or flash the onboard LED when the beam is broken. Or do both at the same time. Leo..

const byte IR_LED = 11; // IR transmitter LED with 100ohm (minimum) CL resistor
const byte IR_Receiver = 8; // from receiver output
const byte onboard_LED = 13; // onboard indicator LED
boolean receiverState;

void setup() {
  pinMode (onboard_LED, OUTPUT);
  pinMode (IR_LED, OUTPUT);
  pinMode (IR_Receiver, INPUT);
  // from Nick Gammon
  TCCR2A = _BV (COM2A0) | _BV(WGM21);
  TCCR2B = _BV (CS20);
  OCR2A =  209; // ~209 = ~38kHz | ~219 = ~36kHz

void loop() {
  receiverState = digitalRead (IR_Receiver);
  if (receiverState == HIGH) { // beam interrupted
    digitalWrite(onboard_LED, LOW); // green onboard LED off
  else { // beam detected
    digitalWrite(onboard_LED, HIGH); // green LED on

I have to beam 20mt far in bright day, the thing i’m trying to build is something like this:


This things have to be quite powrfoul becoause you can’t count on proper aim between the reciver and receiver, diustance can be far therfore all this stuff in terms of power are normally overkills.
I will check the leds you were mentioning, about the code i think i’m ok with irlib but thanks anyway.

Diode removed and i’ve put now 6 leds in 2 strings.

The LED I have mentioned has a narrow beam, and has to be aimed accurately. Maybe not what you want. The receiver I mentioned has a wider opening angle, so positioning that one is easier. Keep daylight/sunlight out of the receiver by mounting it at the end of a short (1") black tube, about the diameter of the receiver lens. Bright light on the transmitter LEDs is not a problem. I think you should aim for 30meters in bright daylight if you want it to be reliable at 20meters. Leo..

I've seen is very narrow and also appers to be discontinued, thans for the tips. Cheers.