Designing a super complex single LED illuminator *Updated*

[DivineChaos]

Hey guys, New to this excellent forum you have here. I feel that this place would be the most ideal place to ask electronics related questions to a project that I have going on.

I will describe what I am trying to do:

I am attempting to design (with your help), single or multiple Infrared LED(s), lit by two AA sized batteries. I wish for this setup to be very bright, very efficient (85% or better) and have constant brightness with varying battery capacity down to 1.6 volts and to produce a single visible "spot" to be able to be picked up by a sensor no less than 15 feet away and at a very wide viewing angle.

My wishes:

1. I wish for a single on/off momentary switch. - TBD how to do this.  The TPS60205 appears to have a momentary on/off input...

1.5. A small green blue LED nearby that depicts "On" state. Obviously id like this to consume as little power as possible. - Handled by the TPS60205's "power good" signal

2. I wish for a "on time" selection button so that the device automagically powers off after a certain period time of 2, 4, or 6 hours, indicated by 3 low power consuming LED's marked 2, 4, or 6 respectively. Only one LED to be lit at a time. Color could vary but Red preferred. - HMMM not sure yet on how to implement this, or if the most efficient use of "logic"

3. A "Low battery" flashing LED, at about 1 flash for 1 second every 2 seconds, that kicks on at about 25% battery life for two rechargeable NiMh batteries while the device is "on". I'm guessing this is at about 2.2 volts? - Handled by the TPS60205, well the part that signals the low voltage anyway - Still need to figure out the flashing part

4. Automatic shut-off at about 1.6 volts. - I think this is handled by the TPS60205's minimum input voltage. Just shuts itself off right? Or do I need to make sure that it shuts off before the minimum voltage?

4.5.   An "the battery is dead" LED that indicates that it is in "too little power" mode when the power button is pressed. - If the power is too low to power the TPS60205, how do I tell the "low power LED" to light up for that moment that you are pressing the button?

I also wish to use cheap, off the shelf items that can be readily purchased from basically any electronics shop.

Seems super complicated and a bit over my head, not too complicated with the right parts, but with your help, I can accomplish this goal. I know enough about connecting circuits to get myself into trouble, to have it have all the features, that's what I need help with.

UPDATE:

The chosen IR LED:

TBD but i'm leaning towards:

Vishay, VSMY3940X01-GS08
IR
PLCC-2
Beam Angle: 120 deg
If - Forward Current:    100 mA

http://www.mouser.com/Search/ProductDetail.aspx?R=VSMY3940X01-GS08virtualkey61370000virtualkey78-VSMY3940X01-GS08

The chosen  DC/DC Switching Regulator:

Texas Instruments, TPS60205
Regulated 3.3-V Low Ripple Charge Pump with Power Good Indicator
 
http://www.ti.com/product/TPS60205/technicaldocuments

The chosen low battery and power good LED's:

Power Good:
Vishay, VLMB41P1Q2-GS08
Blue 
PLCC-2
If - Forward Current:    10 mA
http://www.mouser.com/Search/ProductDetail.aspx?R=VLMB41P1Q2-GS08virtualkey61370000virtualkey78-VLMB41P1Q2

Low Battery:
Vishay, VLMK31R1S1-GS08
Red 
PLCC-2
If - Forward Current:    10 mA
http://www.mouser.com/Search/ProductDetail.aspx?R=VLMK31R1S1-GS08virtualkey61370000virtualkey78-VLMK31R1S1

The chosen "device(s)" for auto shutoff and mode selection:

TBD

[Simon]

sounds easy enough, what are you current skills. Are we helping you or doing it for you ?

[DivineChaos]

sounds easy enough, what are you current skills. Are we helping you or doing it for you ?

I have a few skills, but this is my first "official" project other than messing with an Arduino, programming it and lighting a few LED's with it. I want to try and get away from using a chip that "does it for me" and create a hardware based solution. I have great researching skills, but combining several things at once into a single "product" is where I am having the most difficulty. Also selecting the correct components gives me a headache and I'd like to improve upon those skills.

I'd like as much help as you guys are willing to give. If just "giving me the answer" is what the path leads to, I'd like as much prodding and explaining as possible before that happens.

[Simon]

Well you need to check the minimum safe voltage for your batteries, it's certainly not 1.6V.

Do you want to do the timer with a micro controller (the arduino will do) ?

You need to look up constant current source in order to get something that will drive the LED's with constamt power regardless of battery voltage. What power of LED's are we talking about ?

[DivineChaos]

Well you need to check the minimum safe voltage for your batteries, it's certainly not 1.6V.

- The minimum safe voltage for each individual NiMh cell that I have looked into is about .8v per cell. So for 2 cells, 1.6v?

Do you want to do the timer with a micro controller (the arduino will do) ?

- I think the Arduino will probably consume a bit too much power right? I am trying to consume as little power as possible, I.E. not using a resistor to power the main LED etc.. I do not know the most optimal solution for this, if a microcontroller is optimum, then so be it right?

You need to look up constant current source in order to get something that will drive the LED's with constamt power regardless of battery voltage. What power of LED's are we talking about ?

- I am unsure about what power I should select for the main LED. It just needs to be pretty bright and visible at wide angles at about 15 feet away in a lit room.

I was looking at the TPS61093 from texas instruments for the main LED because of the low input voltage. I'd like to avoid something so small because I will be hand soldering this project and possibly upon success, creating my own PCB

[alsetalokin4017]

Since you will need more than 1.6 volts to drive the LEDs you will need some kind of boost converter if you want the system to run down to that supply voltage.

If you want to use discrete components rather than a microprocessor the thing will be pretty complex all right, to handle all the various functions you've stated. But it might be pretty simple if you choose to use something like an arduino pro-mini 3.3 volt to do the heavy lifting (once you've got the boost converter part sorted.)

You haven't said whether it would be permissible to use PWM or pulsing on the LEDs. If so, using something like the AP2502 linear current-sink, with pulses on the Enable pin, might be an efficient way to drive the LED(s).

For bright white LEDs it's hard to beat the Philips LumiLeds for efficiency.

Just for fun:

[Paul Price]

The real problem with your requirements for this project is that you want to accomplish this with "off the shelf" parts and this requirement is rather vague..does this mean your local electronics shop has MCU's for sale?

If you use a voltage converter chip like the Microchip MCP1640 it would allow you to deliver a constant voltage to the IR LED's and a MCU over the full range of battery voltage.

If you use a quad-comparator like a LM339 you can adjust each a threshold to light just one of several indicators at four different threshold voltage.

However, when it comes to setting 2,4 or 6 hour on-time, it is is easy to see that all your design goals could be so simply combined and implemented by use of a single PICC MCU. For instance, it could wake up from very low power sleep to make measurements and use very little power.

The same MCU could easily use A2D to measure battery voltage and light the correct LED or flash it on at a low duty cycle to show battery states, etc. 

To save battery life while still giving a enough power to a LED to light in the presence of considerable ambient light, an MCU could brightly flash the "On" or any other of your indicators to show your device operations and yet it could save battery by just lighting the LED's for a fraction of a second every so many seconds.

[DivineChaos]

Since you will need more than 1.6 volts to drive the LEDs you will need some kind of boost converter if you want the system to run down to that supply voltage.

If you want to use discrete components rather than a microprocessor the thing will be pretty complex all right, to handle all the various functions you've stated. But it might be pretty simple if you choose to use something like an arduino pro-mini 3.3 volt to do the heavy lifting (once you've got the boost converter part sorted.)

- I just have a feeling that using a microprocessor like the arduino is overkill for a project like this and I'd like to keep the cost down, just in case I have to make a million of these.

You haven't said whether it would be permissible to use PWM or pulsing on the LEDs. If so, using something like the AP2502 linear current-sink, with pulses on the Enable pin, might be an efficient way to drive the LED(s).

- Lighting the LED in the most efficient way possible is the only requirement, it it used as a light source only, so PWM is permissible.

For bright white LEDs it's hard to beat the Philips LumiLeds for efficiency.

Just for fun:

I'm going for an infrared LED. 940nm - 950nm. The ones I've looked at need about 1.3v forward voltage, so I may not need boost converting. Any suggestions on a discreet voltage and current regulator that's "off the shelf"?

[DivineChaos]

The real problem with your requirements for this project is that you want to accomplish this with "off the shelf" parts and this requirement is rather vague..does this mean your local electronics shop has MCU's for sale?

I have a Fry's electronics that has a rather large selection of discreet components, along with Radioshack

So basically, the easiest way to perform all of these functions and using the fewest components, and being the most energy efficient, is to use a Microcontroller? Keep in mind that even with the MCU, ill need to regulate the current and voltage of the LED to keep it at a constant brightness correct?

SO basically,
Battery > Boost converter > Regulator > MCU > Status LED's and swtiches

[Paul Price]

That's the ticket!

If you have one NiMH battery it's voltage will be too low too quickly, if you use two, the voltage will be too high at full charge..you need voltage regulation but a  linear approach would be very inefficient. You will also need a stable voltage as a reference to measure and accurately indicate battery voltage. A MCU using PWM is the most-efficient way to drive the IR LED's at a constant brightness.

[DivineChaos]

That's the ticket!

If you have one NiMH battery it's voltage will be too low too quickly, if you use two, the voltage will be too high at full charge..you need voltage regulation but a  linear approach would be very inefficient. You will also need a stable voltage as a reference to measure and accurately indicate battery voltage. A MCU using PWM is the most-efficient way to drive the IR LED's.

Ok, so lets talk about where we are at so far.

I need to "boost" the battery voltage to a usable voltage efficiently
 -Lets talk about how to do this effectively with the fewest components. I've seen single chip solutions that boost voltage and regulate it, but they are too small to work with

I'm going to need a "low power" MCU that while keeping the LED on, consumes little power, and that can be hand soldered and isn't too much overkill.
 -Suggestions on what to use?

I'm going to need voltage and current regulation that is efficient
 -Suggestions as to what components to look for?

I need a "bright" but not too power hungry Infrared LED with a decent viewing angle
 -Suggestions as to which LED to use? Or should I scrap the single LED and go with multiple LED's pointed in different directions?

I'll also need multiple (approx 5) very low power LED's for the various statuses.
 
I have an Arduino Pro Mini, and I have an FTDI USB to Serial/UART TTL adapter for programming purposes. I also have an "ok" hobby selection of discreet components and various microchips.

[Paul Price]

Think size matters, but in this case, smaller is better.
The MCP1640 gives  you the voltage regulation, the MCU gives you the most efficient current regulation using PWM for powering the IR LED's. Unfortunately, it is trapped within a tiny SOT-23 package..seems no one is making them any bigger. You can buy a small-tippled soldering iron 1mm tip to do the job of sticking it to a tiny PCB so easy.
The PIC16F886 MCU is available in a skinny-dip 28-pin and so easy to solder or breadboard and program or perfboard or PCB-it and it has a built-in oscillator, needs no external xtal,  and it is ideal for the job with super low-power modes.

A good source of efficient IR LED's is to salvage them from orphaned remote controls. The idea is to use at least two of them, and in series, so that the supply voltage is boosted to light them both. RadioShack LED's are not always the brightest on an infrared xmas tree and are over-priced.

[alsetalokin4017]

AP2502, data sheet attached below.

It's a SOT-23-6 package but isn't too hard to solder manually. You can easily find breakout boards to convert the SOT23 to 6 or 8-pin DIP for ease of handling if you need to.

It will maintain constant 20 mA current (at 100 percent duty cycle) in your LEDs over the supply voltage range you are concerned with. The current will not vary more than a few hundred microamps over the entire supply voltage range, if that much. That might be way too bright if you use a superefficient LED, so you can PWM the 2502's Enable pin with your mcu. One AP2502 will support 4 LEDs (but all are controlled by the single Enable pin). If you need more current you can parallel the channels of the 2502 (giving 20, 40, 60 or 80 mA to a single LED).

This would be a possible solution for constant current driving of the LEDs if you go the discrete route. If you decide to use the boost-converter + Pro Mini (or other mcu solution), you can still use the 2502 instead of current-limiting resistors for the LEDs, but you'd use one 2502 per LED and use its Enable pin to turn the LED on or off and to regulate its brightness.

[Richard Crowley]

I am attempting to design (with your help), single or multiple Infrared LED(s), lit by two AA sized batteries. I wish for this setup to be very bright, very efficient (85% or better) and have constant brightness with varying battery capacity down to 1.6 volts

So break this down in to separate pieces that can be researched and developed independently, then you can integrate all the parts together into your desired gadget.  Have you identified the IR-LED that you think you want to use?  How much voltage and current does it want when operating at your desired output brightness?  Do your two AA cells have enough power capacity (mWH) to do that for 6 hours?
Have you identified a boost circuit to drive your IR-LED?  How efficient is it?  What does that mean for your desired 6-hour battery operation?

and to produce a single visible "spot" to be able to be picked up by a sensor no less than 15 feet away and at a very wide viewing angle.

Have you identified a sensor?  How bright does your IR-LED need to be to meet your distance/angle requirements?  Under what conditions does this need to operate?  Running at night is very different than trying to compete with direct sunlight during the day.

Is the purpose of this exercise ILLUMINATION?  Or is it DETECTION?  You say "sensor" so that makes me think this is detection. If you had said "camera", then I would have thought you were talking about illumination. 

Since you have not revealed what this project is supposed to DO, I question your requirement for continuous operation. Would intermittent flashing serve the same detection purpose without burning up so much battery power with continuous operation?  Furthermore, if your IR is going to be competing with sunlight, you may need to modulate it anyway in order to select it out of the background radiation.

How bright do your "user interface" LEDs need to be?  Are you expecting to be able to see them in direct sunlight?  Will this be used only at night?

Can you use a some kind of passive phosphorescent device that is illuminated by the IR-LED to eliminate the "running" indicator LED?

Do your 2-4-6 hour indicators need to be lit the whole operating time?  Or only for a few seconds after turn-on/time-selection?

For that matter, why do you need 3 separate LEDs?  A single LED could flash once for 2 hours, twice for 4 hours, and 3 times for 6 hours, etc.  Your fancy UI and your requirements for ultra-low power seem to be at odds with each other.

For that matter you could do the entire "UI" with a single visible LED.  It comes on and indicates the selected operating time, and then goes off for the remainder of the operation, coming on again if the battery goes low, etc.

Your desire to do all this with discrete components seems both beyond your current abilities (likely more complex than you think), as well as quite outdated. Here in the 21st century it is trivial to do all that with a tiny microcontroller that costs <$1  While, even if you are lucky, a discrete component design will almost certainly draw more current than a low-power very small microcontroller. 

Frys may or may not have all the components you need. Most of us don't have a Frys available locally and just use the internet to order whatever we need.  I have even ordered components from Amazon that I couldn't find at Frys, Mouser, Digikey, or even Ebay!

[SL4P]

What's the magical sensor going to be?
Is it electrically associated with the LED driver module?  Lenses etc?
Both these details can affect your methods or driving and sensing the IR signal.
It may get easier - or harder !

EDIT: Bugger!  Richard you beat me to it on the sensor!
Also - depending on the application - you may be able to use a retroreflector setup instead of direct illumination of the sensor.

[DivineChaos]

Richard, first off thanks for the reply and the specific questions. Ill do my best to answer your questions.

Have you identified the IR-LED that you think you want to use?

 

 - Nothing specific yet. I have a collection of random IR LED's sitting around, but when viewed with a cellphone camera, you can only just barely see the light when within about 15 degrees of direct front viewing and completely invisible about 6 feet away. I'm looking for something that will last considerably longer than 6 hours. Capacity of the current batteries I will use is 2500mah, and am looking for a constant run time of about 30 hours.

Have you identified a boost circuit to drive your IR-LED?  How efficient is it?  What does that mean for your desired 6-hour battery operation?

- I have had a couple suggestions on the boost circuit, but again nothing specific. The MCP1640 looks good so I might stick with it.

Have you identified a sensor?  How bright does your IR-LED need to be to meet your distance/angle requirements?  Under what conditions does this need to operate?  Running at night is very different than trying to compete with direct sunlight during the day.

- The sensor will need to be able to pick up on the IR light about 15 feet from it in a lit bedroom. The sensor will always be pointed in the direction of the light. There will never be direct sunlight to compete with. Just a lit bedroom. So its for detection, but must be lit constantly. Visibly, if you were to look at a normal LED, say, a red one, it would need to appear "ON", so it does not need constant illumination and can be PWM controlled. My goal is 30 hours continuous use.

How bright do your "user interface" LEDs need to be?  Are you expecting to be able to see them in direct sunlight?  Will this be used only at night?

- Dim enough to be forgettable if stared at with the naked eye in a dimly lit bedroom, but bright enough to be seen in a brightly lit bedroom. PITA I know.

Can you use a some kind of passive phosphorescent device that is illuminated by the IR-LED to eliminate the "running" indicator LED?

- IF its cheap, sure. It only needs to be able to let a user know that it is on.

Do your 2-4-6 hour indicators need to be lit the whole operating time?  Or only for a few seconds after turn-on/time-selection? For that matter, why do you need 3 separate LEDs?  A single LED could flash once for 2 hours, twice for 4 hours, and 3 times for 6 hours, etc.  Your fancy UI and your requirements for ultra-low power seem to be at odds with each other.

- Only long enough to let the user know which mode is selected. I figured 3 LED's because it is quicker to establish the run time. By ultra low, my aim is for about 50mA

[DivineChaos]

What's the magical sensor going to be?
Is it electrically associated with the LED driver module?  Lenses etc?
Both these details can affect your methods or driving and sensing the IR signal.
It may get easier - or harder !

EDIT: Bugger!  Richard you beat me to it on the sensor!
Also - depending on the application - you may be able to use a retroreflector setup instead of direct illumination of the sensor.

Since I am probably going to just need to spill the beans, ill go ahead and do it.

I am upgrading a Wii lightbar to be wireless and usable on large TV's and projectors. Since optimal configuration for a Wii lightbar is 1/3rd screen width on either side of the screen, and about 1/16th screen height above,  for a 40 inch TV id need a lightbar about 3 feet wide and 3 inches thick. Very inconvenient. There is a wireless Wii lightbar that exists currently, but with 4AA batteries it dies with about 6 hours of constant use and contains 10 IR LED's arranged very inefficiently to "point" two very small IR LED's in any position you might be in. This does not work well and it makes for some VERY headache inducing "where is my cursor" events.
All that is required is two dots for positioning.

I plan on making a light "pod" that emits the required light and can be positioned anywhere because it is wireless. The Wii remote lasts about 30 hours, so I think 30 hours is a good time to hit for how long it needs to be illuminated.

Hopefully this sheds some "light" on the subject.

[DivineChaos]

For the LED I was thinking on the lines of something like this:

http://www.digikey.com/product-detail/en/MTPS9067MT/1125-1052-ND/2798918

100 degree viewing angle with 30ma consumption  (I think) But the 650nm may be a problem. I think I need 940nm or better

http://www.digikey.com/product-detail/en/IR11-21C%2FTR8/1080-1350-1-ND/2676084

this one looks better but 65mA consumption.

[alsetalokin4017]

FWIW... I just tested this 935nm IR LED-phototransistor combo with a Pro Mini. It works at 15 feet distance, even though the LED looks "dim" in my cellphone camera.

Mouser part number 828-OPS666

I used an AP2502 to limit the current in the LED to 20 mA and supplied the power with a supercapacitor charged initially to 5 V.

[DivineChaos]

FWIW... I just tested this 935nm IR LED-phototransistor combo with a Pro Mini. It works at 15 feet distance, even though the LED looks "dim" in my cellphone camera.

Mouser part number 828-OPS666

Dim is far better than the "not at all" i'm getting with the default setup. 10 mA is a nice consumption. When looking at it with your cellphone camera, can you walk around the room and still see it at various angles?

[alsetalokin4017]

FWIW... I just tested this 935nm IR LED-phototransistor combo with a Pro Mini. It works at 15 feet distance, even though the LED looks "dim" in my cellphone camera.

Mouser part number 828-OPS666

Dim is far better than the "not at all" i'm getting with the default setup. 10 mA is a nice consumption. When looking at it with your cellphone camera, can you walk around the room and still see it at various angles?

The detection angle is pretty narrow at the maximum distance, true.  You have to be pointed fairly accurately at the sensor.

[kony]

Let me guess - motion capture suit? Why not the other way then - lighthouse system is not fancy enough? I'd consider spreading few readymade photodiode senosros to be eaiser.

And by lighthouse I mean this: .

Edit: Ok, mabye when not only for rigid bodies .

[Zero999]

With an LED, the current needs to be regulated, rather than the voltage.

Your phone camera will have an IR filter so will be a poor detector.

Two AA batteries may not store enough energy to meet your requirements. Do you have room for four?

The comparator on an MCU can be used to make a buck constant current driver for the LEDs.

[DivineChaos]

With an LED, the current needs to be regulated, rather than the voltage.

Your phone camera will have an IR filter so will be a poor detector.

Two AA batteries may not store enough energy to meet your requirements. Do you have room for four?

The comparator on an MCU can be used to make a buck constant current driver for the LEDs.

Only have room for 2. I am still searching for a good boost converter for the proper MCU to operate this device. The forward voltage of the main LED's aren't the problem because being IR they are very low, looking at 1.2 V. The other LED indicators are the problem and the MCU I am guessing. I'm going to start selecting some components and get back to this thread

- EDIT

I modified the original post to reflect on some discoveries