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LED strobe light

A

Anthony Fremont

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


You'd be very mistaken.

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

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

I agree, but depending upon how you define the "right tool". Price,
size, multiple manufacturers, circuit simplicity/reliability, power
consumption etc. IMO micros can meet all those, especially price.
Hell, you can buy 32 bit ARMs now for around $1. A PIC running at 32kHz
consumes less power than the self-discharge rate of a typical battery,
it doesn't even have to sleep. Even resistors cost money, copying
software is free after the one-time investment. How long would it take
to design a 556 out of a circuit vs. porting <100 instructions to
another micro? How about the manufacturing impact?
Unless the strobe led needs to be remote controlled, I see no reason for a
uC.

That's just an arbitrary requirement, it has nothing to do with
selecting the "right tool" AFAICT.
 
S

Spehro Pefhany

Jan 1, 1970
0
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

You could require..

- precise (crystal) adjustable control of flash rate
- adjustment of phase without affecting flash rate



Best regards,
Spehro Pefhany
 
A

Anthony Fremont

Jan 1, 1970
0
Pooh Bear said:
Farnell has them in ones for GBP 0.26.

Digikey has them at a qty prcing of USD 0.14

I can't seem to find that out there. I do see qty 10000 for USD .43
(IMO ridiculously steep for the capability/precision, unless output
current is everything to you). Isn't GBP .26 about four or five times
USD 0.14. If I was buying 10000 PICs I bet I could get them for less
than .43.
Show me a uC for under 50 cents ( never mind under 14 cents ).

AIUI, the going rate for 8 pin or less 8-bit micros is in the 40 cents
range. Though I don't know what they cost, surely many 4-bit micros
would come in lower than that.
Show me a uC that has 200 mA drive capability.

You got me there, but here's one with 330mA drive capability.
http://www.fujitsu.com/downloads/MICRO/fma/pdf/e713723.pdf

How much is a 100mA transistor in qty? ;-)
 
R

RHRRC

Jan 1, 1970
0
Pooh said:
Farnell has them in ones for GBP 0.26.

Digikey has them at a qty prcing of USD 0.14



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

I dont know the relevance of all this to the origional post but to
throw some more numbers about a production quantity price for a pic10
is around 19 cents US.
If you want any accuracy a 555 is not going to achieve it at a sensible
cost but I suspect that accuracy better than 5% is not required for a
flashing led.
On the other hand running a pic from a rail above ~5.5V costs extra.

As an aside has anyone ever used a 555 in a production piece of
equipment?
They have been going for years and so must be used but who (besides
hobbyists) uses them and for what?
I have seen a couple of product uses -just as astables- but only
because, I suspect, that the volumes were relatively small and, judging
from the overall design, a more economical design may have stretched
the design capabilities.
 
M

martin griffith

Jan 1, 1970
0
On 12 Feb 2006 13:27:56 -0800, in sci.electronics.design "RHRRC"

snip
As an aside has anyone ever used a 555 in a production piece of
equipment?
They have been going for years and so must be used but who (besides
hobbyists) uses them and for what?snip

Revox/Studer in precision capstan servos in professional tape decks.
Worked like a dream


martin
 
K

Ken Smith

Jan 1, 1970
0
RHRRC said:
As an aside has anyone ever used a 555 in a production piece of
equipment?

Back in the mists of time, I used one as part of a DC-DC circuit. It was
a wide range DC-DC.

A common problem with such things is that if you connect them to a supply
that rises slowly, they try to come up while the supply is still rising.
Although the input may be able to supply enough Watts when it gets up to
voltage, it may not be able to supply enough current at the lower voltage.
I used the LM555 to make a startup delay and an undervoltage cut out.

The PWM part was done by a LM339.
 
P

Pooh Bear

Jan 1, 1970
0
Anthony said:
I can't seem to find that out there.

http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=5569&Row=156687&Site=US

0.128 @ 12k pcs.
I do see qty 10000 for USD .43
(IMO ridiculously steep for the capability/precision, unless output
current is everything to you). Isn't GBP .26 about four or five times
USD 0.14.

About. But Farnell sells them one off - no minimum order - virtually
guaranteed ex-stock availability and includes next-day shipping. Perfect for
protoytping but not for production.

The listed Digikey price is roughly what I'd have extrapolated from the one
off Farnell figure.
If I was buying 10000 PICs I bet I could get them for less
than .43.

I've heard about 50 cents mentioned here.
AIUI, the going rate for 8 pin or less 8-bit micros is in the 40 cents
range. Though I don't know what they cost, surely many 4-bit micros
would come in lower than that.

Never come across any 4 bit jobs. I'd guess there's almost no demand now in
view of low cost 8 bit devices.

You got me there, but here's one with 330mA drive capability.
http://www.fujitsu.com/downloads/MICRO/fma/pdf/e713723.pdf

How much is a 100mA transistor in qty? ;-)

A 100 mA transistor isn't what's needed.

Graham
 
P

Pooh Bear

Jan 1, 1970
0
RHRRC said:
I dont know the relevance of all this to the origional post but to
throw some more numbers about a production quantity price for a pic10
is around 19 cents US.

Can you point to a supplier offering that pice ?

I searched Digikey and the best price I saw was 0.579
http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=6486&Row=248448&Site=US
As an aside has anyone ever used a 555 in a production piece of
equipment?

No but I've used 4538s though.

Graham
 
S

Spehro Pefhany

Jan 1, 1970
0
equipment?
They have been going for years and so must be used but who (besides
hobbyists) uses them and for what?

Watchdog timer for an i8749 ucontroller. Made lots of those things.
Thermistor PI temperature controller module (really, a long time ago).
We made tons of industrial timers, but the 555 is not suitable for
that application- discretes are much better.
I have seen a couple of product uses -just as astables- but only
because, I suspect, that the volumes were relatively small and, judging
from the overall design, a more economical design may have stretched
the design capabilities.

Would you have a visceral objection to paralleling all the pins on an
8-bit port?


Best regards,
Spehro Pefhany
 
P

Pooh Bear

Jan 1, 1970
0
Spehro said:
I wrote :


Would you have a visceral objection to paralleling all the pins on an
8-bit port?

Not at all. A PIC10 only has 4 I/O pins though.

Graham
 
A

Anthony Fremont

Jan 1, 1970
0
Pooh Bear said:

Ok, didn't see em. I was looking at LMs for some reason.
About. But Farnell sells them one off - no minimum order - virtually
guaranteed ex-stock availability and includes next-day shipping. Perfect for
protoytping but not for production.

The listed Digikey price is roughly what I'd have extrapolated from the one
off Farnell figure.


I've heard about 50 cents mentioned here.


Never come across any 4 bit jobs. I'd guess there's almost no demand now in
view of low cost 8 bit devices.

I think there's plenty still being used out there probably mostly in
small, cheap toys.
A 100 mA transistor isn't what's needed.

Oops, typo there.
 
R

Rich Grise

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

But, it sounds like Jamie is talking about a "strobe", as in those
"timing lights", or those disco things. To make something like that, you
need either a xenon flashtube or a _REALLY_ bright LED that can be driven
to its limits, with an extremely narrow, very energetic, pulse; ergo, in
either case, he's going to need more than a 5V supply and probably more
mA than a 555 can source.

Cheers!
Rich
 
G

GregS

Jan 1, 1970
0
But, it sounds like Jamie is talking about a "strobe", as in those
"timing lights", or those disco things. To make something like that, you
need either a xenon flashtube or a _REALLY_ bright LED that can be driven
to its limits, with an extremely narrow, very energetic, pulse; ergo, in
either case, he's going to need more than a 5V supply and probably more
mA than a 555 can source.

You need a pulse length program. The frequency is constant. When it full on, the continuous max duty
of the LED will have to be observerd. You also need a control, pot, or some sensor which the
processor will measure. A power fet can interface the LED to processor.

greg
 
E

electronic-eng.com

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

Hi Jamie

I have an LED circuit and assembly program using the PIC12F675 on the
link below. You will need to adjust the delay subroutine to give you
100Hz, the circuit will deliver around 100mW but for more power just
add a transistor or FET to the LED drive line and put the LED cathode
to GND. Email me from the contact page on the site if you would like
the .hex file or more specific information about this circuit.

http://www.electronic-eng.com/pic/picprog001.html

Best regards
Alan
www.electronic-eng.com
 
E

electronic-eng.com

Jan 1, 1970
0
Just thinking about this a bit more fundamentally, an LED flashing at
100Hz would look like a constantly on LED as if driven by a DC source,
but a bit dimmer (RMS of 100Hz signal). The human eye samples at around
50-60Hz so anything above this just starts to blur, TV's and monitors
are >50Hz and you can't see in between frames, that is unless you have
a crap TV ;)

Alan
www.electronic-eng.com
 
P

Pooh Bear

Jan 1, 1970
0
Rich said:
But, it sounds like Jamie is talking about a "strobe", as in those
"timing lights", or those disco things. To make something like that, you
need either a xenon flashtube or a _REALLY_ bright LED that can be driven
to its limits, with an extremely narrow, very energetic, pulse; ergo, in
either case, he's going to need more than a 5V supply and probably more
mA than a 555 can source.

His post ( above ) says 1 watt.

Graham
 
R

Rich Grise

Jan 1, 1970
0
Back in the mists of time, I used one as part of a DC-DC circuit. It was
a wide range DC-DC.

A common problem with such things is that if you connect them to a supply
that rises slowly, they try to come up while the supply is still rising.
Although the input may be able to supply enough Watts when it gets up to
voltage, it may not be able to supply enough current at the lower voltage.
I used the LM555 to make a startup delay and an undervoltage cut out.

The PWM part was done by a LM339.

So, are you going to show us the schematic, or keep us all on tenterhooks? ;-)

A power-on reset sounds like kind of a cool use for a 555, if there
weren't such things as, oh, say:
http://www.digikey.com/scripts/DkSearch/dksus.dll?Criteria?Ref=2392&Site=US&Cat=32965736
;-)

Cheers!
Rich
 
B

Bob Monsen

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.

http://home.comcast.net/~rcmonsen/Strobe.ps

This was a design for some guy who wanted 3 or 4 flashes every couple of
seconds. Use a trimmer to replace R5, and you can adjust the frequency
with it. Change R1 to a smaller value, and you can get more energy into
the flashes...

Note that if you change R1, ensure that your LEDs can support the
additional current of the pulses...

There is a simulation here

http://home.comcast.net/~rcmonsen/Strobe.asc

For LTSpice (which is a free spice program from linear technologies
http://www.linear.com/software)

Feel free to replace the 555 with a microcontroller... you can drive the
FET directly with a microcontroller port. Raise the port for about 50
microseconds, then lower it to flash the LEDs.

More LEDs mean more total energy can be in each pulse without burning up
the LEDs. You could probably use a single Luxeon Star to replace them all;
in that case, get rid of the resistors. Note the direction the LEDs are
pointing too...

--
Regards,
Bob Monsen

Science without religion is lame, religion without science is blind.
Albert Einstein, "Science, Philosophy and Religion: a Symposium", 1941
 
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