High power IR transmitter question

[MoRoH]

Hello,


I need a high power IR transmitter to driver a TSAL7200 or TSAL6100 IR LED. I have a 555 timer circuit set up that will put out a 30Khz signal 3 times a second (i hope). It will be received by a TSOP4330 receiver module(30kHz).

I need to amplify the output using a transistor to get almost 1A of current delivered to the IR LED. I'm unsure where to connect the transistor.

attached is my schematic and calculations

 

[blueroomelectronics]

Take a look here Robot Room - Infrared Emitter from CMOS 555

PS a single IR LED will probably burn out with more than 100ma pulsed going through it. What LED are you going to use?

 

[Boncuk]

Driving an IR-LED with 1A the LED will be fried with first arriving pulse.

Instead using one LED use 10 in an array. High power LED torches have at least 6 LEDs connected three serial and two of those sets parallel.

100mA for an LED is already hard at the limit. Giving enough recovery time between bursts they should do it.

Take care of sufficient cooling.

Boncuk

 

[Nigel Goodwin]

I can't comment on this specific IR LED, but it's normal practice to pulse IR LED's in remote controls at about 1A - and they are perfectly reliable at that.

In this case the 555 won't provide anywhere near that, will it? - even if it does, if the pulse are infrequent enough (so it meets IR remote type specs) it will be fine.

 

[MoRoH]

Forward current = 100mA
peak forward current = 200mA
surge forward current = 1.5A


Blueroomelectronics: Thanks, that schematic is helpful, do you think a regular 555 timer would have enough output to for the transistor to amplify it enough. Or would i need like a Darlington pair type configuration.

Bonuk: Thanks ill look into doing that

Nigel: I've also head of TV remotes being pulsed at 1A and this IR Led (Vishay TSAL7200) if any would be able to handle it i think. I will be sending a 30khz pulse 3 times a second..I plan on amplifying the 555 timer output with a transistor.


Thanks guys

 

[audioguru]

The max output current from a 555 timer is 200mA. use a transistor to boost it.
The max duty-cycle of the high current drive to the IR LED is stated on its datasheet.

I could not find a TSOP4330 but most other TSOP IR receivers have an automatic-gain-control that reduces its gain a lot when the IR pulses are not in certain bursts of pulses with a certain pause between bursts.

 

[Boncuk]

If you are planning to exceed a forward current of 100mA I strongly recommend to connect the LED with the cathode to the timer output and the anode via a current limiting resistor to V+.

With the given R and C values the timer output signal has a duty cycle of approximately 70%. Connecting the LED as shown in the schematic you must not exceed the nominal forward current of 100mA.

Driving it up to 200mA the duty cycle might be 50% with an ON-time of 100µs.

To stay well within limits use two IR-LEDs connected in series (Uf=1.35V) and adapt the current limiting resistor accordingly.

Boncuk

 

[MoRoH]

Thanks guys,

Sorry for not responding lately, My GF is home for a week, but thats for the replies.

I've updated my circuit..basically here my plan...put a pot on the base of the transistor, see how much power i can deliver to my LED before it blows...then take a bit off..HAHA i have 15 so. Goood ol T&E.

Will this circuit work, i beleive i have the transistor connected right? and also if i hook up more than one IR LED like botnuk suggested, will i be able to get more range do you think?

suggestions? i didin't figure out any R values yet but thats minor.

Thanks

 

[audioguru]

You have the transistor connected so it turns off the LED by shorting it.
Usually a transistor is connected to turn on an LED.

EDIT:
Nope. The transistor will do nothing because pin 3 output of the 555 is shorted to ground.
The 555 will smoke and burn.

 

[MoRoH]

oppps, there how bout this..

Thank you


EDIT: If i made the Collector the resistor a pot (instead of base resistor) it would control Pt delivered to the LED right?

 

[audioguru]

Why do you want to burn out an LED? The next one will not be exactly the same so it might burn out with less or more current. Look at the spec's on the datasheet and select a current that is allowed.

If you use a pot in series with the LED then unless it is a huge monster it will burn out before the LED does.

Pin 4 of the 555 on the right must connect to the positive supply.

You forgot to look at the datasheet for the IR receiver to see why it will not work with 30kHz pulsed at 3Hz. It needs bursts of 30kHz and a certain pause in between bursts.

 

[Boncuk]

Hi audioguru,

I simulated the timing of the circuit. The low frequency astable produces a freqency of 2.5 to 3Hz. The high frequency astable is adjustabe up to more than 50KHz and will work properly if adapted to the receiver frequency.

Hi MoRoH,

the power side of your application should look somewhat like that. You can connect up to three IR-LEDs in series at a VDD of +5V. Use a cluster of nine LEDs for maximum range and adjust transmitting frequency exactly to match the receiver frequency.

The sample circuit's current limiting resistor is calculated for two IR-LEDs in series. The formula for the calculation is contained in the schematic. Adapt the value of RL if you are using three IR-LEDs.

Boncuk

 

[MoRoH]

Thanks guys!

Audioguru:
1) thanks for the tip on pin 4, i was unsure of where to connect that.
2) as far as i know, from what i understood by reading the data sheets and specs of my TSOP4830 receiver module and my TSAL7200 IR LED, the receiver module has a carrier of 30KHz so i set 1 555 timer to 30KHz. The other one i set to 3Hz giving the appropriate pause between the 30Khz pulses.


Boncuk:

1)Thanks for the tips and the schematic/calc. I will do some more research and let you guys know what i come up with.

 

[MoRoH]

Boncuk, on your schematic what exactly is the pot for on the base of the transistor, what will it adjust?

Thanks

 

[MoRoH]

Questions? can i make a TSOP4830 receiver module output an analog voltage from like 0-5v? or does it only work in on/off/pulses?

 

[Boncuk]

Boncuk, on your schematic what exactly is the pot for on the base of the transistor, what will it adjust?

Thanks

It adjusts the base voltage, hence the base current resulting in different collector current.

Boncuk

 

[Boncuk]

It just switches from high to low when receiving a valid signal.

Boncuk

 

[audioguru]

TSOP IR receiver ICs are digital. The output is either high or low.