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LED strobe light

J

Jamie Morken

Jan 1, 1970
0
Hi,

What would be the simplest circuit to control the frequency and
brightness of an LED (100Hz maximum at 1watt max power) with
microcontroller control.

cheers,
Jamie
 
J

John_H

Jan 1, 1970
0
Jamie said:
Hi,

What would be the simplest circuit to control the frequency and
brightness of an LED (100Hz maximum at 1watt max power) with
microcontroller control.

cheers,
Jamie

Simplest:
Microcontroller directly drives a logic-level-input MOSFET, turns on at
the 100Hz (or lower) repitition rate, turns off at a time to determine
brightness. If you turn on the LED for 1 ms, it will be half as bright
than if you turn it on for 2 ms. Current limit the LED from a fixed
supply through an appropriate resistor.
 
P

Pooh Bear

Jan 1, 1970
0
Jamie said:
Hi,

What would be the simplest circuit to control the frequency and
brightness of an LED (100Hz maximum at 1watt max power) with
microcontroller control.

The *simplest* circuit hardly requires a microcontroller !

Graham
 
M

martin griffith

Jan 1, 1970
0
The *simplest* circuit hardly requires a microcontroller !

Graham
Then use a PIC, slightly better than a 555


martin
 
P

Pooh Bear

Jan 1, 1970
0
martin said:
Then use a PIC, slightly better than a 555

A 555 has enough oomph to drive a led directly at a decent current
though.

Graham
 
S

Spehro Pefhany

Jan 1, 1970
0
A 555 has enough oomph to drive a led directly at a decent current
though.

Graham

Typical 1W Luxeon LEDs need 350mA, which is a bit much for a 555.


Best regards,
Spehro Pefhany
 
P

Pooh Bear

Jan 1, 1970
0
Spehro said:
Typical 1W Luxeon LEDs need 350mA, which is a bit much for a 555.

Is that '1W rating' a typical Luxeon spec ?

Graham
 
B

Boris Mohar

Jan 1, 1970
0
Is that '1W rating' a typical Luxeon spec ?

Graham

Yes and there are also bigger ones. If you really want to go nuts try
Lamina which can go over 100W (red) Digikey 521-1006-ND
 
S

Spehro Pefhany

Jan 1, 1970
0
Is that '1W rating' a typical Luxeon spec ?

Graham

Kind-of. They have I/II/V models that have input power of roughly
1W/3W/5W, and that's how they are often marketed. The V Star type are
700mA at 6.8V typical. The I Star ("1W") are only 350mA @ 3V-3.4V
typical.



Best regards,
Spehro Pefhany
 
K

Keith

Jan 1, 1970
0
The *simplest* circuit hardly requires a microcontroller !

Nonsense! Perhaps you'd better read the requirements statement
again; "with microcontroller control".
 
P

Pooh Bear

Jan 1, 1970
0
Keith said:
Nonsense! Perhaps you'd better read the requirements statement
again; "with microcontroller control".

Which is why I phrased my answer as I did.

Graham
 
K

Keith

Jan 1, 1970
0
Which is why I phrased my answer as I did.

Geez Pooh, I thought you were a businessman. He asked for a solution
*specifically* using a microcontroller and here you are telling him that
it's the wrong solution. Perhaps he already has one in the design?
Sometimes a microcontroller *is* the right answer (particularly when the
customer asks for one).
 
A

Anthony Fremont

Jan 1, 1970
0
Geez Pooh, I thought you were a businessman. He asked for a solution
*specifically* using a microcontroller and here you are telling him that
it's the wrong solution. Perhaps he already has one in the design?
Sometimes a microcontroller *is* the right answer (particularly when the
customer asks for one).

Especially when it only costs $1 and can control BOTH the perceived
brightness (via high rate PWM) and the strobe rate. You'd need a 556 to
do that and they're $1.44 single qty at DigiKey. ;-)
 
P

Pooh Bear

Jan 1, 1970
0
Keith said:
Geez Pooh, I thought you were a businessman. He asked for a solution
*specifically* using a microcontroller and here you are telling him that
it's the wrong solution.

I have often found that ppl are chasing the wrong solution, usually on the
basis of bad advice or incorrect assumptions.
Perhaps he already has one in the design?
Sometimes a microcontroller *is* the right answer (particularly when the
customer asks for one).

The OP asked for simple.

Quite often ppl get 'wrapped up in technology' for the sake of it and simple
becomes not so simple. If we knew *why* he wanted a uC maybe it would make
more sense ?

Graham
 
P

Pooh Bear

Jan 1, 1970
0
Anthony said:
Especially when it only costs $1 and can control BOTH the perceived
brightness (via high rate PWM) and the strobe rate. You'd need a 556 to
do that and they're $1.44 single qty at DigiKey. ;-)

You have some funny ideas ideas about the price of commodity ICs.

Graham
 
K

Keith

Jan 1, 1970
0
I have often found that ppl are chasing the wrong solution, usually on the
basis of bad advice or incorrect assumptions.

Perhaps it's you who have the incorrect assumptions?
The OP asked for simple.

UCs *are* simple. Transistors are free. It's the packaging that cost$. ;-)
Quite often ppl get 'wrapped up in technology' for the sake of it and simple
becomes not so simple. If we knew *why* he wanted a uC maybe it would make
more sense ?

It makes sense because that's what he asked for. Maybe you want to ask
for the whole problem, rather than assume a UC is the wrong solution?
 
A

Anthony Fremont

Jan 1, 1970
0
Pooh Bear said:
Anthony Fremont wrote:

You have some funny ideas ideas about the price of commodity ICs.

How's that? What are you paying for 556's? It seems only natural as
micros come down in price that they will displace more and more of the
specialty market. This can only drive the price up further on those
parts. I'd say that you need to face the fact that microcontrollers are
going to be the chip of choice for the future, even if it does seem like
overkill.
 
A

Anthony Fremont

Jan 1, 1970
0
Keith said:
Perhaps it's you who have the incorrect assumptions?


UCs *are* simple. Transistors are free. It's the packaging that cost$. ;-)


It makes sense because that's what he asked for. Maybe you want to ask
for the whole problem, rather than assume a UC is the wrong solution?

Here here! I get the idea that Pooh doesn't "dig" micros, period.
 
P

Pooh Bear

Jan 1, 1970
0
Anthony said:
Here here! I get the idea that Pooh doesn't "dig" micros, period.

You'd be very mistaken.

I have actually designed in micros where they once would have seemed an
unusual choice.

It's a question of the right tool for the job.

Unless the strobe led needs to be remote controlled, I see no reason for a
uC.

Graham
 
P

Pooh Bear

Jan 1, 1970
0
Anthony said:
How's that? What are you paying for 556's?

Farnell has them in ones for GBP 0.26.

Digikey has them at a qty prcing of USD 0.14

It seems only natural as
micros come down in price that they will displace more and more of the
specialty market. This can only drive the price up further on those
parts. I'd say that you need to face the fact that microcontrollers are
going to be the chip of choice for the future, even if it does seem like
overkill.

Show me a uC for under 50 cents ( never mind under 14 cents ).

Show me a uC that has 200 mA drive capability.

Graham
 
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