motion activated LED array

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b3l

Newbie level 5
I would like to have a motion activated IR LED array. I found simple instructions to make a battery operated IR light which would be installed outdoors, but how can I make it respond to motion? I have a motion sensing transmitter and receiver set model #HS3600. The receiver plugs into a household outlet and will turn on whatever is plugged into it for 5 min. when motion is detected. Is there a way to make the sensor and receiver parts work to activate this LED array outside? Simple instructions for a complete novice would be really appreciated.

mturna

Junior Member level 2
I don't know much about this sensor and IR communication but I think you can arrange their (led & receiver's ) position such that if the receiver receives signal from the led no motion case else it means positon of led is changed or something cut the signal which is motion case. After that you can use receiver as a switch for no motion case and open switch for motion case close switch. I hope, it will help you.

Super Moderator
Staff member
Do you want to power your IR led array from battery only? Keep in mind that it will be in standby mode most of the time as it waits to detect a signal to switch on. Drawing battery power continually. Power may not be available when you want it.

Can you run house current to your IR led array? Then you could plug it into the unit that runs on house current. But you'd need to protect it from the elements. Because it's risky to run house current outdoors.

b3l

Newbie level 5
Ideally, I would run from battery, there is no power out there. I could perhaps use a bigger battery? However, it may be possible to use the light indoors and shine it out a window... though I'm not sure how well that will light the area. If that works then batteries wouldn't be necessary but I have no clue how to rig it for house power.

---------- Post added at 19:14 ---------- Previous post was at 18:53 ----------

I was thinking about the suggestion to plug the light into the receiver... Is it possible to just swap out white LEDs with infrared in an already manufactured LED light that runs on house current? Hrmm, then again, are there any that run on house current... most are flashlight type lights... I will have to look around.

Super Moderator
Staff member
White led's run on a different voltage than IR led's. You'd need to know exactly how much voltage and current is available.

Is your IR led array the type used in night-vision and nighttime photography? They use equipment that might suit your purposes. Such as batteries, triggering circuitry.

To power the led's from house current will require careful attention to what the power supply puts out. LED's are easy to ruin by running overmuch current through them.

b3l

Newbie level 5
My IR LED array is intended for night webcam surveillance but I haven't built it yet. This is what I was looking to build.

Unfortunately I have no information on the LEDs as they were from a surplus store that had no specs for them. The guys at the store said I could just swap them with white LEDs but that sounded too simple.

It states in the instructions that the outlet on the receiver part of the motion detector system can control up to 600 watts of incandescent lighting... if that info is of any use.

Super Moderator
Staff member
The video shows a 9 V battery powering 5 white led's. This is straightforward. You should be able to go a similar route with IR led's.

However you should start with maybe 10 IR led's in series. They conduct on a lower voltage than white led's. So you can put more IR's in series. Don't arrange them in parallel until you get an idea how many is safe to use in series first.

Check with an ammeter to see if any current is flowing through 10 in series.

If not then remove one led at a time until some current flows. When you read between 20 and 30 mA, that's the number of led's to use as a start. Internet forums talk as though 40 or 70 or 100 mA is okay. It will be wise if you wait on drawing higher current until you know you need more lumens.

You can experiment to see how much current makes an led warm. Or if you're willing to sacrifice an led or two then see when one gets too hot to hold between your fingers. Running overmuch current through led's shortens their useful life.

Problem #2 is to send a signal from your motion detector. Problem #3 is to detect it at a distance.

The simplest way is to plug a wall wart into your motion detector outlet, then string a low voltage cable across the yard. However you don't seem to want to do that.

So if you absolutely need to be covert, then you'll need to transmit a signal by light or sound or radio.

A low-cost laser pointer could send a beam to a light detector inside your IR unit. This won't be easy to get to work. You'll need to get power into the laser pointer, from a suitable wall wart plugged into your motion detector. You'll need to construct a detector circuit inside your IR unit. It would be based on a phototransistor or photodiode or cadmium sulfide cell. It would turn on a mosfet or transistor or relay to turn on the IR leds.

A laser pointer may be unfeasible for some reason such as ruining the detector. Then a narrow beam led might do instead. But then your detection network will need to be adjusted to be so sensitive that daylight would trigger it. Therefore you'd have to go out each night and switch it on. And go out again before dawn and switch it off.

To transmit a signal by sound will be even more difficult to manage.

b3l

b3l

Points: 2

bigdogguru

Unfortunately I have no information on the LEDs as they were from a surplus store that had no specs for them.

Here's a datasheet for 5mm IR LEDs:

5mm IR LED Datasheet

What is the diameter of your IR LEDs? I could probably dig up a datasheet for them. Are there any other marks on the LEDs?

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b3l

b3l

Points: 2

b3l

Newbie level 5
I thought that perhaps the motion detector receiver might have components inside that could be worked into the LED setup but it seems that isn't possible so I agree, "The simplest way is to plug a wall wart into your motion detector outlet, then string a low voltage cable across the yard". So that is perhaps the best option, considering my limited understanding of electronics.

How do I go about adding a wall wart to the IR LED design from the video? It is indeed IR, not just white LED and I don't think I would need anything stronger than what is shown in the video.

My IR LEDs are 5mm transparent light purple and the prongs are bent at a 90 degree angle to the bulb. There are no other markings on them.

---------- Post added at 10:20 ---------- Previous post was at 10:13 ----------

If IR LEDs run on a lower voltage than white LEDs then could I simply swap out the white LEDs for the IR LEDs in a commercially constructed LED light?

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bigdogguru

Thanks,

I fixed it as well.

b3l, if you can measure the diameter of the IR LEDs, I can most likely find a corresponding datasheet. It would give you some idea of current and voltage specifications, which would allow you to design array circuit and power source.

Super Moderator
Staff member
How do I go about adding a wall wart to the IR LED design from the video? It is indeed IR, not just white LED and I don't think I would need anything stronger than what is shown in the video.

My IR LEDs are 5mm transparent light purple and the prongs are bent at a 90 degree angle to the bulb. There are no other markings on them.

---------- Post added at 10:20 ---------- Previous post was at 10:13 ----------

If IR LEDs run on a lower voltage than white LEDs then could I simply swap out the white LEDs for the IR LEDs in a commercially constructed LED light?

The video shows 5 led's running from a 9V battery. And they're bright.

The older bright white led's draw 3.6V. So specs seem to have changed.

It's quite possible you can simply substitute the IR for the white. There's a reason for caution however. You want to avoid frying any led's. So you need to measure how much current goes through them when powered by whatever supply you use.

And you don't necessarily need regulated DC from one of the $25 wall warts at your local electronics store. You can get by with simple stepped down AC. Say 8 to 10 volts AC. The IR led's will provide their own reverse-voltage blocking. It's just that you must not overdrive your led's. And I wouldn't necessarily believe the voltage printed on the label. Wall warts can be way off in that regard. Often higher than the label. That's where caution is needed. So what's the easiest thing to do? Get one of the DC adapters that has a choice of voltage settings: 3, 4.5, 6, 7.5, 9, and 12. You slide a switch to choose what you want. It will let you experiment with different numbers of led's and different voltages. Even better would be a DC adapter with a knob where you can dial the exact voltage you need. So if you find that 5 led's isn't bright enough, such an adjustable supply will be sufficiently versatile that you can try two strings of 3 led's each, or 4 led's each. Etc. One more thing to allow for. If you string a few dozen feet of wire between the power source and the led's, you may lose a volt or two just from the effect of added resistance. Last edited: b3l Newbie level 5 Thank you to all of you for your advice. BradtheRad, in the video he is using 5 10mm triple chip 200mW IR LEDs in series... not just plain LEDs. He is also using a 10ohm 1/4W 5% Carbon Film Resistor and a 9V battery. A nice simple design for me but I guess the question is will it be bright enough with the smaller LEDs that I have and do I need a different design with different resistor, etc. I already have a DC adapter that has the adjustable switch. However, where I am stuck now is how do I go about attaching it to the circuit? Do I just leave the battery out and solder the adapter to the resistor instead or is there a special socket/outlet that I can solder in so the adapter is removable? bigdogguru, the LEDs I have are 5mm across... is that what you mean or do I need to measure around the bulb. My IR LEDs are 5mm transparent light purple and the prongs are bent at a 90 degree angle to the bulb. There are no other markings on them. My apologies if I seem thick, I am a true novice but some of what has been posted to me is seeping in. ---------- Post added at 10:57 ---------- Previous post was at 10:50 ---------- This solar powered fixture would be ideal if only the LEDs were infrared. I may pick it up and if I can get it open without damage, would someone be willing to try to help me alter it for infrared or is that a silly idea considering that I am a complete novice? I do know how to solder, but that's about it... and I have no multimeter or those types of tools, though I suppose I could borrow them or buy... though I'm really trying to do this project on the cheap. BradtheRad Super Moderator Staff member 1. A multimeter, even an inexpensive one, will be one of the most useful things you could have in your toolbox. You can check batteries, house voltage, vehicle voltage, whether a bulb is good or shot, etc. I've seen a digital type on sale for$9 at out local Menard's. I don't know whether it's made in China.

2.

You should have at least two 10 ohm resistors on hand. The video uses a 10 ohm with a 9V battery. That's the sole reason the video project is easy: because the 9V battery is stable and predictable.

One volt more and those led's would fry. One volt less and they'll go dim. So that's why you may need to add 20 ohms resistance instead of just 10.

The led's in Bigdogguru's link have a maximum spec of 50 mA max. This is a reasonable max for your led's. It's crucial to the success of your project.

Even 50 mA could be too much, or at least it could shorten their useful life. Better to use a lot of led's at low current, than a few led's at high current.

I think you'll end up needing two strings of led's anyway. Ten total.

3.

DC adapters normally have either a co-ax power plug, or a 1/8 inch phone plug. You need to use a jack specifically mated to the plug.

The co-ax comes in different sizes which are hard to distinguish with a ruler (let alone the naked eye). Radio Shack has the various sizes.

You'll solder the jack same as the guy in the video does with the battery leads. The jack has tabs. You'll solder on the wires coming from the led's. You must make sure you attach the wires at the same polarity which matches your DC adapter.

Or do you intend to add several feet of wire between the adapter and your led box? In that case it's easier to just clip off the plug and solder wires directly. Forget about buying a jack.

You can install the plug and jack later if you wish.

4.

How will you know when current is flowing through the IR led's? Their light is invisible. Therefore consider adding a visible led inline with the IR type. It's an easy way for you to verify things are working.

However the led must be able to handle the same current going through the IR. Note that ordinary visible led's typically have a max spec of 20 mA. So you'd need to use a high power type. Just one more item for you to think about.

bigdogguru

bigdogguru, the LEDs I have are 5mm across... is that what you mean or do I need to measure around the bulb.

Sorry b3l, I did not notice you had mentioned the size in the previous post. I also hadn't realized Sparkfun had mistakenly switched the LED datasheet with the wrong type.

Here is the correct 5mm IR LED datasheet, as you can see these LEDs can have a maximum If = 100mA, however an If = 20mA is a typically level. The datasheet also show a photo of IR LED, have the purple or blue tint as b3l described.

The major problem with these types of devices is their limited lifespan, typically a 1000 hours of operation, not many days at 6-8 hours of continuous operation.
A typical design to drive these IR LEDs use PWM to increase the degree of brightness control and the lifespan of the device. But, implementing a PWM source maybe a little above your current capabilities, unless you could find a canned design.

The selection of a proper current limiting resister is critical to ensure you do not shorten their lifespan prematurely. A 20mA forward current (If), with a typical voltage drop (Vd) of 1.3v across the diode and a 9v supply voltage (Vs) would require a 385 ohm resistance or 390 ohm standard value resistor.

You can use the formula:

Rcl = (Vs - Vd)/If

Or if you do not care for math, this online calculator:

Current Limiting Resistor Calculator for Leds

By the way, the "calculator" above can be used to calculate the current limiting resistor for a multiple LED series design like your LED Booster in the video.

Hope the info helps, with your design.

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b3l

Newbie level 5
Thank you both very much for all your input. I understand enough now that I think I can go ahead with this project. I will let you know how it goes... and may come back for more advice as I go along.

Thanks again!

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