LED strobe light

You could require..

- precise (crystal) adjustable control of flash rate

- adjustment of phase without affecting flash rate

Best regards, Spehro Pefhany

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perceived

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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.

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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.

You got me there, but here's one with 330mA drive capability.

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

About a penny, in one thousand lots.

Jon

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.

snip

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

martin

In article , RHRRC wrote: [....[

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.

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kensmith@rahul.net   forging knowledge

?Ref=5569&Row=156687&Site=US

0.128 @ 12k pcs.

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.

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

Graham

Can you point to a supplier offering that pice ?

I searched Digikey and the best price I saw was 0.579

?Ref=6486&Row=248448&Site=US

No but I've used 4538s though.

Graham

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.

Would you have a visceral objection to paralleling all the pins on an

8-bit port?

Best regards, Spehro Pefhany

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"it\'s the network..."                          "The Journey is the reward"
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Not at all. A PIC10 only has 4 I/O pins though.

Graham

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ICs.

?Ref=5569&Row=156687&Site=US

Ok, didn't see em. I was looking at LMs for some reason.

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I think there's plenty still being used out there probably mostly in small, cheap toys.

Oops, typo there.

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

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

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.

Best regards Alan

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

His post ( above ) says 1 watt.

Graham

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:

?Ref=2392&Site=US&Cat=32965736 ;-)

Cheers! Rich

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

For LTSpice (which is a free spice program from linear technologies

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...

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Regards,
  Bob Monsen

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