Hi guys,

I need to adapt a little LED torch from a standard LED light to an
Infra-red LED. It's all very simple, but I don't know what sort of IR
LED to get. The current LED just has one pin touching the batteries and
the other bent back to make contact with the switch when it's on. The
batteries are 2 x CR2032 3V Lithium batteries. Can anyone tell me what
sort of rating IR LED I would need to get as a replacement I can't see
any writing on the current LEDs to get a clue?

--
regards, James Luff
Gamertag: Lufferov
"There are 10 types of people in the world:
Those that understand binary, and those that don't."

In article <5ud23aF1cibi1U1@mid.individual.net>,
James Luff <lufferov@gmail.com> wrote:

> Hi guys,
>
> I need to adapt a little LED torch from a standard LED light to an
> Infra-red LED. It's all very simple, but I don't know what sort of IR
> LED to get. The current LED just has one pin touching the batteries and
> the other bent back to make contact with the switch when it's on. The
> batteries are 2 x CR2032 3V Lithium batteries. Can anyone tell me what
> sort of rating IR LED I would need to get as a replacement I can't see
> any writing on the current LEDs to get a clue?

There generally isn't any writing to be found.

If the driver is controlling current, just get the polarity of the new
LED correct, and pretty much any IR LED should work - if scavenging, the
optical encoders in mechanical computer mice provide two good IR LEDs -
or just buy any suitable one. With a current driver, ANY LED should be
fine.

If it's controlling voltage, and the present LED is white, you could be
in for trouble - but voltage control is a lousy way to drive LEDs
anyway, as they are not well-specified in voltage, but very well
specified in current.

--
Cats, coffee, chocolate...vices to live by

Ecnerwal wrote:
> In article <5ud23aF1cibi1U1@mid.individual.net>,
> James Luff <lufferov@gmail.com> wrote:
>
>> Hi guys,
>>
>> I need to adapt a little LED torch from a standard LED light to an
>> Infra-red LED. It's all very simple, but I don't know what sort of IR
>> LED to get. The current LED just has one pin touching the batteries and
>> the other bent back to make contact with the switch when it's on. The
>> batteries are 2 x CR2032 3V Lithium batteries. Can anyone tell me what
>> sort of rating IR LED I would need to get as a replacement I can't see
>> any writing on the current LEDs to get a clue?
>
> There generally isn't any writing to be found.
>
> If the driver is controlling current, just get the polarity of the new
> LED correct, and pretty much any IR LED should work - if scavenging, the
> optical encoders in mechanical computer mice provide two good IR LEDs -
> or just buy any suitable one. With a current driver, ANY LED should be
> fine.
>
> If it's controlling voltage, and the present LED is white, you could be
> in for trouble - but voltage control is a lousy way to drive LEDs
> anyway, as they are not well-specified in voltage, but very well
> specified in current.
>

Thank, but I'm new to all this so:

<------ your explanation

/"""""""\
| o o |
(| " |) <- My head
| --- |
\_____/

What's a driver? How do I get the polarity right? If what's controlling
voltage?

There's just a single sliding switch on the torch and two pins from the
LED, one to - on the battery and the other to the switch.

--
regards, James Luff
Gamertag: Lufferov
"There are 10 types of people in the world:
Those that understand binary, and those that don't."

James Luff wrote:

[snip]

> What's a driver? How do I get the polarity right? If what's controlling
> voltage?
>
> There's just a single sliding switch on the torch and two pins from the
> LED, one to - on the battery and the other to the switch.

If you're absolutely certain there are no
other components in the circuit, the 'driver'
he's referring to may be built into the LED
itself.

If that's the case, you may have to experiment
with an IR LED and some resistors to find
something that will work in your torch...

HTH

Randy Day wrote:
> James Luff wrote:
>
> [snip]
>
>> What's a driver? How do I get the polarity right? If what's controlling
>> voltage?
>>
>> There's just a single sliding switch on the torch and two pins from the
>> LED, one to - on the battery and the other to the switch.
>
> If you're absolutely certain there are no
> other components in the circuit, the 'driver'
> he's referring to may be built into the LED
> itself.
>
> If that's the case, you may have to experiment
> with an IR LED and some resistors to find
> something that will work in your torch...
>

Yep, the circuit couldn't be simpler, so the driver (still don't know
what a driver actually is) may be built into the LED I guess. Is there a
way to check? Think I'll just pop down to Maplins, buy an IR LED and
just see what happens, the worst I can do is bugger up the LED which
will cost me next to nothing anyway.

--
regards, James Luff
Gamertag: Lufferov
"There are 10 types of people in the world:
Those that understand binary, and those that don't."

James Luff wrote:
>[...](still don't know what a driver actually is)[...]

http://www.google.com/search?q=define:driver
http://en.wikipedia.org/wiki/Driver_(el ... _component)

In article <5ud7dnF1gr4hpU1@mid.individual.net>,
James Luff <lufferov@gmail.com> wrote:

> What's a driver? How do I get the polarity right? If what's controlling
> voltage?

A circuit to control the current or voltage being fed from the battery
to the LED.

> There's just a single sliding switch on the torch and two pins from the
> LED, one to - on the battery and the other to the switch.

...and what, if anything, is on the other side of the switch? If it's
wired directly to the other side of the battery, then there is no driver
as such (or it's remotely possible that there's something built into the
base of the LED - but then the LED would look a bit different than the
standard LED.) That would be a simple, failure-prone, but cheap
(consumer goods like cheap, especially if the maker is well-insulated
from customers) method of voltage control, dependent on the voltage of
the batteries being low enough that the LED won't draw too much current.

If the switch is connected to the other side of the battery by a
resistor, that's a simple, though inefficient, form of current limiting,
still somewhat dependent on the operating voltage of the LED.

http://en.wikipedia.org/wiki/Resistor

A White LED tends to operate at a relatively high voltage - in either of
these cases you might burn out a IR led swapped in - but as you say,
they are cheap, so give it a try. Might try it with only one battery at
first, which would cut the voltage in half.

The longer lead of a new LED should be the lead that is connected to the
positive side of the battery.

http://en.wikipedia.org/wiki/LED

If there's some sort of slightly more complex looking lump (often
enclosed in epoxy or plastic) there might be a more sophisticated driver
controlling the current - or not. Never can tell with consumer goods
until you dissect them.

--
Cats, coffee, chocolate...vices to live by

In article <5ud23aF1cibi1U1@mid.individual.net>, James Luff wrote:
>
>I need to adapt a little LED torch from a standard LED light to an
>Infra-red LED. It's all very simple, but I don't know what sort of IR
>LED to get. The current LED just has one pin touching the batteries and
>the other bent back to make contact with the switch when it's on. The
>batteries are 2 x CR2032 3V Lithium batteries. Can anyone tell me what
>sort of rating IR LED I would need to get as a replacement I can't see
>any writing on the current LEDs to get a clue?

I think go for infrared LEDs based on output and having a beam width or
beam angle that appears good (or is about the same as that of the visible
LEDs if any secondary optics exist), and having overall dimensions about
the same as those of the existing visible LEDs. I give a fair to high
chance that if you pop out the visible LEDs and pop in the infrared ones,
things work out at least largely A-OK.

Battery life will probably decrease, since IR LEDs generally have a
lower voltage drop than visible ones and if current is unregulated they
will draw more current. They can also take more current, due to lower
voltage drop (and also accordingly thicker bonding wires since a given
wattage requires more current due to lower voltage drop).

Sorry, warranty is limited to refund of what I got paid by unsatisfied
readers (showing a receipt or cancelled check) to post this!

- Don Klipstein (don@misty.com)

On Jan 6, 8:17 pm, Ecnerwal <LawrenceSM...@SOuthernVERmont.NyET>
wrote:
> In article <5ud7dnF1gr4h...@mid.individual.net>,
> James Luff <luffe...@gmail.com> wrote:
>
> > What's a driver? How do I get the polarity right? If what's controlling
> > voltage?
>
> A circuit to control the current or voltage being fed from the battery
> to the LED.
>
> > There's just a single sliding switch on the torch and two pins from the
> > LED, one to - on the battery and the other to the switch.
>
> ..and what, if anything, is on the other side of the switch? If it's
> wired directly to the other side of the battery, then there is no driver
> as such (or it's remotely possible that there's something built into the
> base of the LED - but then the LED would look a bit different than the
> standard LED.) That would be a simple, failure-prone, but cheap
> (consumer goods like cheap, especially if the maker is well-insulated
> from customers) method of voltage control, dependent on the voltage of
> the batteries being low enough that the LED won't draw too much current.

Yes, that seems to be how these el-cheapo 1-to-1.5" LED flashlights
are being made. I remember measuring a few i-v points on one of these
a year or so ago, it resembled a bare LED with no current limiting.
The internal resistance of the batteries is the only current limit
here.



> If the switch is connected to the other side of the battery by a
> resistor, that's a simple, though inefficient, form of current limiting,
> still somewhat dependent on the operating voltage of the LED.
>
> http://en.wikipedia.org/wiki/Resistor
>
> A White LED tends to operate at a relatively high voltage - in either of
> these cases you might burn out a IR led swapped in - but as you say,
> they are cheap, so give it a try. Might try it with only one battery at
> first, which would cut the voltage in half.

Yes, I'd say definitely start with just one battery and see what
happens.

James, do you have any way of telling if an IR LED would be, in fact,
producing a "sufficient" IR beam in your setup? If not, you could
experiment with a visible red LED, and if things work out then try the
IR LED.

Regards,

Mark

>
> The longer lead of a new LED should be the lead that is connected to the
> positive side of the battery.
>
> http://en.wikipedia.org/wiki/LED
>
> If there's some sort of slightly more complex looking lump (often
> enclosed in epoxy or plastic) there might be a more sophisticated driver
> controlling the current - or not. Never can tell with consumer goods
> until you dissect them.
>
> --
> Cats, coffee, chocolate...vices to live by

On Jan 7, 10:43 am, James Luff <luffe...@gmail.com> wrote:
> Ecnerwal wrote:
> > In article <5ud23aF1cibi...@mid.individual.net>,
> > James Luff <luffe...@gmail.com> wrote:
>
> >> Hi guys,
>
> >> I need to adapt a little LED torch from a standard LED light to an
> >> Infra-red LED. It's all very simple, but I don't know what sort of IR
> >> LED to get. The current LED just has one pin touching the batteries and
> >> the other bent back to make contact with the switch when it's on. The
> >> batteries are 2 x CR2032 3V Lithium batteries. Can anyone tell me what
> >> sort of rating IR LED I would need to get as a replacement I can't see
> >> any writing on the current LEDs to get a clue?
>
> > There generally isn't any writing to be found.
>
> > If the driver is controlling current, just get the polarity of the new
> > LED correct, and pretty much any IR LED should work - if scavenging, the
> > optical encoders in mechanical computer mice provide two good IR LEDs -
> > or just buy any suitable one. With a current driver, ANY LED should be
> > fine.
>
> > If it's controlling voltage, and the present LED is white, you could be
> > in for trouble - but voltage control is a lousy way to drive LEDs
> > anyway, as they are not well-specified in voltage, but very well
> > specified in current.
>
> Thank, but I'm new to all this so:
>
> <------ your explanation
>
> /"""""""\
> | o o |
> (| " |) <- My head
> | --- |
> \_____/
>
> What's a driver? How do I get the polarity right? If what's controlling
> voltage?
>
> There's just a single sliding switch on the torch and two pins from the
> LED, one to - on the battery and the other to the switch.

This is common with those 2032 based LED lights, just the battery and
the LED. It uses the internal resistance of the battery (approx 20
ohms when fresh per cell) to provide the current limiting.
Add a resistor in series with any IR LED you put in there, to limit
the current some more. 100 ohms would be a safe value.

Dave.

In <38e8d3ba-b78d-44c1-9a70-fa4c94b6c219@l1g2000hsa.googlegroups.com>,
David L. Jones wrote:
>On Jan 7, 10:43 am, James Luff <luffe...@gmail.com> wrote:
>> Ecnerwal wrote:
>> > In article <5ud23aF1cibi...@mid.individual.net>,
>> > James Luff <luffe...@gmail.com> wrote:
>>
>> >> Hi guys,
>>
>> >> I need to adapt a little LED torch from a standard LED light to an
>> >> Infra-red LED. It's all very simple, but I don't know what sort of IR
>> >> LED to get. The current LED just has one pin touching the batteries and
>> >> the other bent back to make contact with the switch when it's on. The
>> >> batteries are 2 x CR2032 3V Lithium batteries. Can anyone tell me what
>> >> sort of rating IR LED I would need to get as a replacement I can't see
>> >> any writing on the current LEDs to get a clue?
>>
>> > There generally isn't any writing to be found.
>>
>> > If the driver is controlling current, just get the polarity of the new
>> > LED correct, and pretty much any IR LED should work - if scavenging, the
>> > optical encoders in mechanical computer mice provide two good IR LEDs -
>> > or just buy any suitable one. With a current driver, ANY LED should be
>> > fine.
>>
>> > If it's controlling voltage, and the present LED is white, you could be
>> > in for trouble - but voltage control is a lousy way to drive LEDs
>> > anyway, as they are not well-specified in voltage, but very well
>> > specified in current.
>>
>> Thank, but I'm new to all this so:
>> <SNIP cute graphic made out of text>
>> What's a driver? How do I get the polarity right? If what's controlling
>> voltage?
>>
>> There's just a single sliding switch on the torch and two pins from the
>> LED, one to - on the battery and the other to the switch.
>
>This is common with those 2032 based LED lights, just the battery and
>the LED. It uses the internal resistance of the battery (approx 20
>ohms when fresh per cell) to provide the current limiting.
>Add a resistor in series with any IR LED you put in there, to limit
>the current some more. 100 ohms would be a safe value.

My experience is that IR LEDs are rated for 50 milliamps or more.
Typical voltage drop at that current is roughly 2.2 volts less than
typical voltage drop of white LEDs at their maximum rated current.

2.2 / .05 is close enough to 47 ohms.

More appropriate may be to draw 80 mA from fresh "coin cells" or 50 mA
from ones in "average condition and at end of a 30 second usage period"
and measure the voltage at that point. Subtract 1.4 volts from higher of
these, and didvide that by the amount of current that the LEDs can take
for a little while (I suspect generally 75 mA for IR ones) and that is the
minimum appropriate resistor. Not that I actually tried this, but I give
some chance of this indicating 39 or 33 ohms (maybe even less) if using
"coin cells" that are typically used in "keychain LED flashlights".

For that matter, I have heard of IR LEDs with 100 mA rating. Also, I
have yet to blow an LED with current 5/3 times its "absolute maximum"
rating, though its life expectancy could well be reduced quite a bit (from
100,000 hours for most other than white, UV, violet, purple and pink).

Just keep in mind that with an IR LED, the greater current draw means
shorter battery life. And most LED "keychain flashlights" won't give
full-blast performance for long. You may want two AAA or AA cells and a
33 ohm (conservative) or 22 ohm (a little aggressive) resistor.

- Don Klipstein (don@misty.com)

David L. Jones wrote:
> On Jan 7, 10:43 am, James Luff <luffe...@gmail.com> wrote:
>> Ecnerwal wrote:
>>> In article <5ud23aF1cibi...@mid.individual.net>,
>>> James Luff <luffe...@gmail.com> wrote:
>>>> Hi guys,
>>>> I need to adapt a little LED torch from a standard LED light to an
>>>> Infra-red LED. It's all very simple, but I don't know what sort of IR
>>>> LED to get. The current LED just has one pin touching the batteries and
>>>> the other bent back to make contact with the switch when it's on. The
>>>> batteries are 2 x CR2032 3V Lithium batteries. Can anyone tell me what
>>>> sort of rating IR LED I would need to get as a replacement I can't see
>>>> any writing on the current LEDs to get a clue?
>>> There generally isn't any writing to be found.
>>> If the driver is controlling current, just get the polarity of the new
>>> LED correct, and pretty much any IR LED should work - if scavenging, the
>>> optical encoders in mechanical computer mice provide two good IR LEDs -
>>> or just buy any suitable one. With a current driver, ANY LED should be
>>> fine.
>>> If it's controlling voltage, and the present LED is white, you could be
>>> in for trouble - but voltage control is a lousy way to drive LEDs
>>> anyway, as they are not well-specified in voltage, but very well
>>> specified in current.
>> Thank, but I'm new to all this so:
>>
>> <------ your explanation
>>
>> /"""""""\
>> | o o |
>> (| " |) <- My head
>> | --- |
>> \_____/
>>
>> What's a driver? How do I get the polarity right? If what's controlling
>> voltage?
>>
>> There's just a single sliding switch on the torch and two pins from the
>> LED, one to - on the battery and the other to the switch.
>
> This is common with those 2032 based LED lights, just the battery and
> the LED. It uses the internal resistance of the battery (approx 20
> ohms when fresh per cell) to provide the current limiting.
> Add a resistor in series with any IR LED you put in there, to limit
> the current some more. 100 ohms would be a safe value.

The problem is the little keylight style torch case has no space for a
resistor. Let alone changing the batteries as another poster suggested.

--
regards, James Luff
Gamertag: Lufferov
"There are 10 types of people in the world:
Those that understand binary, and those that don't."

On Jan 8, 8:40 pm, James Luff <luffe...@gmail.com> wrote:
> David L. Jones wrote:
> > On Jan 7, 10:43 am, James Luff <luffe...@gmail.com> wrote:
> >> Ecnerwal wrote:
> >>> In article <5ud23aF1cibi...@mid.individual.net>,
> >>> James Luff <luffe...@gmail.com> wrote:
> >>>> Hi guys,
> >>>> I need to adapt a little LED torch from a standard LED light to an
> >>>> Infra-red LED. It's all very simple, but I don't know what sort of IR
> >>>> LED to get. The current LED just has one pin touching the batteries and
> >>>> the other bent back to make contact with the switch when it's on. The
> >>>> batteries are 2 x CR2032 3V Lithium batteries. Can anyone tell me what
> >>>> sort of rating IR LED I would need to get as a replacement I can't see
> >>>> any writing on the current LEDs to get a clue?
> >>> There generally isn't any writing to be found.
> >>> If the driver is controlling current, just get the polarity of the new
> >>> LED correct, and pretty much any IR LED should work - if scavenging, the
> >>> optical encoders in mechanical computer mice provide two good IR LEDs -
> >>> or just buy any suitable one. With a current driver, ANY LED should be
> >>> fine.
> >>> If it's controlling voltage, and the present LED is white, you could be
> >>> in for trouble - but voltage control is a lousy way to drive LEDs
> >>> anyway, as they are not well-specified in voltage, but very well
> >>> specified in current.
> >> Thank, but I'm new to all this so:
>
> >> <------ your explanation
>
> >> /"""""""\
> >> | o o |
> >> (| " |) <- My head
> >> | --- |
> >> \_____/
>
> >> What's a driver? How do I get the polarity right? If what's controlling
> >> voltage?
>
> >> There's just a single sliding switch on the torch and two pins from the
> >> LED, one to - on the battery and the other to the switch.
>
> > This is common with those 2032 based LED lights, just the battery and
> > the LED. It uses the internal resistance of the battery (approx 20
> > ohms when fresh per cell) to provide the current limiting.
> > Add a resistor in series with any IR LED you put in there, to limit
> > the current some more. 100 ohms would be a safe value.
>
> The problem is the little keylight style torch case has no space for a
> resistor. Let alone changing the batteries as another poster suggested.

Then you can do without the resistor.
The worst that can happen is you blow your IR LED, which is probably
unlikely anyway.
Or take out one battery, you only need one for an IR LED, there is no
need for the 6V provided by the two batteries.

Dave.