Might add a supply capacitor of 1000 micro farads @ 25V

 

That might do it. The regulators also recommend that they have a 0.1µF cap on the output to prevent oscillation.

 

Will give those a try
I don't think i will be able to add resistors becuz that is reducing my led output to about half.
I'm absolutely sure that the leds are not damaged

I also wanted to bring to your notice something else
If I connect one from the battery and the transimiitng oart from an ac/dc power supply,then htere is no problem,but as soon as any direct electrical connection is made the retriggering starts.Otherwise everything else is working perfectly and as expected

 

I keep saying this, but you're not listening. Resistors are not optional.

 

sorry if you feel that i'm ignoring your advice,i'm not,i have tried using a resistor but the loss is so high that m range is like 5cm from 30cm

what values do you recommend?i'm getting around 4v at the leds.

The battery i'm using is 80Ah!!!!!and still with the two circuits working simultaneously ,there is fluctuation

If nothing else works ,i will have to provide a separate power supply from ac.It works that way!!!!!!

 

Look, I could try to explain why the resistors are so necessary, but I've already done this in the article I wrote.

You are talking about your problem, I have given you your likely cause, but you are so focused in doing it your way (which isn't working) I'm just spinning my wheels.

I'll state it again, your diodes, possibly your transistor, is toast. Resistors are necessary, always. If you want to know why you will have to do some reading. Electronics does not respond well to wishful thinking, you have to follow the rules.

You use the resistors to limit the current the LEDs take, that is what they do. If the LEDs do not work with the proper resistors (whose value is easy to calculate) then they are gone, dead, zapped. No amount of wishing will make it so.

Color of the LEDs is important, it is part of what determines Vf (forward dropping voltage). You are using infrared, so they are likely around 2.1, though this can vary a bit. For a 4V power supply, and 20ma through the LEDs, you will need 100Ω resistors.

The reason your battery is fluxuating is you are shorting it out, through your LEDs.

 

I totally agree with you that resistors are necessary for an led because i myself have fried a couple of them but in this case the switching is supposed to protect the led from frying.

Will putting a bigger transistor help me to manage the high current change.

I'll state the problem again.
The circuits are working perfectly.

1. I don't think i'll be able to add a resistor because the output is not enough.
2. I'm using a remote for the led signal because the 555 astables i built were not able to give me enough power without frying the leds.
3. Using the remote has solved this problem but the current draw is too high.this is causing fluctations.
4. Is it possible to get the same output after reducing the currrent.
5. If not, how can modify the circuit to manage the changing current

PS. the circuits are working perfectly if the inputs are connected independently.( I ve tested it well)

Please don't feel that i'm not heeding your advice.Please let me know if i can get the same output with lower current

 

Switching does not protect LEDs, only resistors do that. Guess my work is done here.

 

IR LEDs generally have a very low Vf (forward voltage), on the order of 1.2 to 1.5v at their rated current. If you try to increase the voltage across the LED without some kind of current limiter (like a resistor), the current will increase dramatically.

If you are switching an array of 8 parallel IR LEDs without current limiting resistors using a transistor, you're practically shorting out the power supply when the transistor turns on.

If you subject any LED to current in excess of it's specifications, you will permanently damage it, causing it to be much dimmer. LEDs can last up to around 100,000 hours, but even when operated within specifications gradually become dimmer over their service life. Operating them at above their rated specifications will cause them to become dim far more rapidly.

Some LEDs you might be able to operate at a 10% duty cycle at significantly higher current than specified; the datasheet for the LEDs in question would need to be consulted. However, IR LEDs in remote controls operate at more like a 20%-30% duty cycle, so don't really qualify for that - and you have NO current limiting in place except for the internal resistance of the power source - in this case, the 7805 regulator.

Your IR LEDs are very likely already damaged due to being subjected to too much current; as a result they will never be as bright as they were before being abused.

Your 7805 regulator is limiting the total circuit current to around 2 Amperes peak. That's probably around 200mA-250mA per LED, if their Vf is perfectly matched - which is unlikely. Once the 7805's peak current limit of 2A is reached, it "folds back" to around 700mA current, or roughly 80mA per LED until the LEDs are turned off.

You need to calculate what the proper size current limiting resistors are for your IR LEDs, and install them after replacing your damaged LEDs.

Rlimit = (VSupply - Vf LED) / DesiredCurrent

If you don't take my advice, you will not have success with your project.

I don't have time to help you with this, as I'm leaving town for a week or two.

 

I totally agree with you that resistors are necessary for an led because i myself have fried a couple of them but in this case the switching is supposed to protect the led from frying.

It's causing the supply to be intermittently shorted via the transistor and LEDs.

Will putting a bigger transistor help me to manage the high current change.

You're already causing the power supply to be folded back (crowbar-ed). Increasing the current draw will only make the problem worse.

I'll state the problem again.
The circuits are working perfectly.

Apparently, they are not. If they were, your timer wouldn't be resetting, and you wouldn't be asking for help, and basically ignoring the helpful responses.

1. I don't think i'll be able to add a resistor because the output is not enough. You need to replace the already-damaged LEDs and use correctly valued current limiting resistors.
2. I'm using a remote for the led signal because the 555 astables i built were not able to give me enough power without frying the leds. Had you used the proper value of current limiting resistors for your LEDs, you would not have fried the LEDs.
3. Using the remote has solved this problem but the current draw is too high.this is causing fluctations. Use current limiting resistors on your LEDs.
4. Is it possible to get the same output after reducing the currrent. Not with damaged LEDs.
5. If not, how can modify the circuit to manage the changing current. Use properly-valued current limiting resistors on each LED.

PS. the circuits are working perfectly if the inputs are connected independently. (I've tested it well)

Please don't feel that i'm not heeding your advice. Please let me know if i can get the same output with lower current

You need to post the specifications of the IR LEDs that you are using (preferably, the datasheet) and a better schematic.

You do not show a resistor on the base of your LED driver transistor, or it's value.
You don't say what transistor you're using.

I really don't have any more time to spend on this.

 

i have tried using a resistor but the loss is so high

What size resistor did you use? What formula did you use to calculate the resistor size?

 

I tried using a 100Ω resistor in series with each of the leds,but as i have said earlier the result was disappointing.
I must confess that i did not try any other values

As for the led specifications, i have no idea because, i bought them from a local store .

• What would be the recommended lowest value such that i would get a really bright output while still protecting the led?

(The input is 4v)

I am extremely sorry if i seemed stubborn(especially to bill marsden)

I didn't know that i could short out my supply like that.thank you for that info.I used the battery thinking that my power supply was not good enough.

The transistor i'm using is 188(I don't know if it still exists because i found it in an old corner of my house)

I also appreciate the time you have spent on my question.

 

I tried using a 100Ω resistor in series with each of the leds,but as i have said earlier the result was disappointing.
I must confess that i did not try any other values

As for the led specifications, i have no idea because, i bought them from a local store.

Well, that should simplify your problem somewhat. Why don't you go back to that store, and ask the store manager for the specifications of the LEDs that you purchased?

What would be the recommended lowest value such that i would get a really bright output while still protecting the led?
(The input is 4v)

I'm not sure where you're getting 4v from, as you're using a 7805 regulator - which should output 5v, if the input voltage is at least 7v under load.

But just "for instance" - if your LEDs have a Vf of 1.4v, and your supply was actually 4v after the transistor, then you'd have 4v-1.4v = 2.6v over which to determine the current. If you used a 100 Ohm resistor, then I = E/R (Current = Voltage / Resistance), so I = 2.6v / 100 Ohms = 26mA.

The transistor i'm using is 188 (I don't know if it still exists because i found it in an old corner of my house)

That doesn't cross-reference to much of anything.