Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old April 30th 18, 07:12 AM posted to sci.electronics.repair
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Default bike headlamp LED, 4.5V (AA), resistor in series needed?

On 4/29/2018 3:50 PM, whit3rd wrote:
On Sunday, April 15, 2018 at 9:30:31 PM UTC-7, Mike S wrote:
On 4/15/2018 8:30 PM, mike wrote:


I was thinking of building a simple voltage/current regulator, and
wondering how much current would be spent in the ct.


Yeah, for battery powered gizmos, that's important.
The easy solution is a funny chip that has a builtin
current regulator, and has (as well as current limit) thermal
protection (when mounted thermally to the LED parts).

Look on eBay for AMC7135 (about 1W delivered to an LED, use two or
three in parallel for higher power lamps).. This is a good solution
for a 4.2V battery input, which a power-wasting resistor can never
improve on. Alas, battery and LED options must be driven by the
choice of such a chip.

$3 for 10!
10pcs AMC7135 350mA LED driver SOT-89
Thank you!


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Old May 6th 18, 01:39 AM posted to sci.electronics.repair
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Default bike headlamp LED, 4.5V (AA), resistor in series needed?

Once upon a time on usenet Mike S wrote:
On 4/29/2018 3:50 PM, whit3rd wrote:
On Sunday, April 15, 2018 at 9:30:31 PM UTC-7, Mike S wrote:
On 4/15/2018 8:30 PM, mike wrote:


I was thinking of building a simple voltage/current regulator, and
wondering how much current would be spent in the ct.


Yeah, for battery powered gizmos, that's important.
The easy solution is a funny chip that has a builtin
current regulator, and has (as well as current limit) thermal
protection (when mounted thermally to the LED parts).

Look on eBay for AMC7135 (about 1W delivered to an LED, use two or
three in parallel for higher power lamps).. This is a good solution
for a 4.2V battery input, which a power-wasting resistor can never
improve on. Alas, battery and LED options must be driven by the
choice of such a chip.

$3 for 10!
10pcs AMC7135 350mA LED driver SOT-89
Thank you!


https://www.aliexpress.com/item/10PC...811284788.html

Just over a buck for 10 there - including shipping.
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)


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Old May 6th 18, 06:44 AM posted to sci.electronics.repair
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Default bike headlamp LED, 4.5V (AA), resistor in series needed?

On 5/5/2018 5:39 PM, ~misfit~ wrote:
Once upon a time on usenet Mike S wrote:
On 4/29/2018 3:50 PM, whit3rd wrote:
On Sunday, April 15, 2018 at 9:30:31 PM UTC-7, Mike S wrote:
On 4/15/2018 8:30 PM, mike wrote:

I was thinking of building a simple voltage/current regulator, and
wondering how much current would be spent in the ct.

Yeah, for battery powered gizmos, that's important.
The easy solution is a funny chip that has a builtin
current regulator, and has (as well as current limit) thermal
protection (when mounted thermally to the LED parts).

Look on eBay for AMC7135 (about 1W delivered to an LED, use two or
three in parallel for higher power lamps).. This is a good solution
for a 4.2V battery input, which a power-wasting resistor can never
improve on. Alas, battery and LED options must be driven by the
choice of such a chip.

$3 for 10!
10pcs AMC7135 350mA LED driver SOT-89
Thank you!


https://www.aliexpress.com/item/10PC...811284788.html

Just over a buck for 10 there - including shipping.


Just ordered them, thank you. Can you recommend a circuit, for 2 AA
batteries? I found several with a quick search, if you have one that has
a very efficient use of current I would like to see it.



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