3 minute light flash

Discussion in 'General Electronics Chat' started by Chessie61, Aug 15, 2015.

  1. Chessie61

    Thread Starter New Member

    Aug 15, 2015
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    I need some help from a pro. Is it possible to build a simple circuit to make an LED light flash once every 3 minutes?
     
  2. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    Of course it is possible. What accuracy do you require and how long should the LED be on for?
     
  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Yes it is generally possible to do that. However, the only details you give out your secret project is "LED" and "3" :confused:

    Now if you uncover the secret LED you wish to use and possible a power source too then some reasonable methods may be offered.

    And welcome to the forums !!!!
     
  4. Roderick Young

    Member

    Feb 22, 2015
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    If it was 20 years ago, I'd recommend a different method, but today, the way I would do it to to buy a PICAXE 08M2. It's an 8-pin chip, and you would need the chip, 3 resistors, and the LED. Plus, you would need a 5-volt power supply (3 AA batteries would do). There is free programming software that can be downloaded, and used to program the chip to flash the LED at just about any rate desired, from thousands of times per second, to a timespan so long, that the power supply is likely to fail before there is a second flash.
     
  5. Chessie61

    Thread Starter New Member

    Aug 15, 2015
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    Thanks for the responses. The Led would only have to flash, not stay on for any prolonged time. The three minute interval is important but does not have to be millisecond accuracy. Within a couple of seconds would be fine. This project is for a missionary friend. I am somewhat of a novice working with circuits. I have a good working knowledge of electronic circuits but not done too many projects. I am actually a watchmaker with a hobbyists interest in electronics. Helps immensely with quartz watch circuitry.
     
  6. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    180s +- 3s is barely doable with a 555 timer. I would use a CD4040 or CD4060 chip. Sorta looks like a timepiece...
     
  7. ian field

    Distinguished Member

    Oct 27, 2012
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    On one occasion I used a blocking oscillator running on a single 1.5V cell to generate a bit more than 34V, that charged up a 47uF capacitor, when it got to about 32 - 34V a diac in series with an LED load triggered and dumped the charge in the capacitor.

    Mine used a bank of 24 parallel LEDs from an old magnetic work light. The flashes were painful to look at!

    For a single LED; the bias resistor for the blocking oscillator could be increased for reduced bias, and then it would take a reasonable flash rate delay to charge a smaller capacitor better suited to a single LED.

    The circuit I built was also tried on a single TO220 style power LED - it was better than the bank of 24 parallel LEDs, despite having come from Maplin.
     
  8. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    How bright? Daylight visible or indoors? Attention-grabbing, or just bright enough to be seen if you're already looking in its direction?

    The 4060 counter is good for only about 4 mA output current with a 5 V supply. Newer high-brightness LEDs will give you a decent blink with 2 mA:

    Counter (4060, 2 R's, 1 C), large coupling capacitor, LED. Select the timing components such that the Q14 output goes low every three minutes. The output stage will provide the current limiting, and the coupling capacitor size sets the blink duration. The LED will come on fast, then dim a bit more slowly.

    ak
     
  9. Chessie61

    Thread Starter New Member

    Aug 15, 2015
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    Thanks for all the help from you pros. As soon as I get a chance to figure out the schematics I will try one of the suggestions.
     
  10. ian field

    Distinguished Member

    Oct 27, 2012
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    If you need precise timing, the blocking oscillator/diac probably isn't for you.

    Its a quick and dirty method that uses very few components.
     
  11. Chessie61

    Thread Starter New Member

    Aug 15, 2015
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    I like your help. What resistors would I need?
     
  12. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    The PICAXE 08M2 is a microcontroller, it needs more than just resistors, it needs to be programmed.

    Alternatively, if you're looking for a solution rather than a project, you could just use one of these:

    http://www.ebay.co.uk/itm/12V-DC-Mu...e-Switch-DT-/171651700911?hash=item27f73d18af

    I have never used one but it looks like it will do what you want in "Cycle mode 1". It think it may even have an LED that illuminates when the relay is activated.
     
  13. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    A 555 IC, 3 min. timer works quite well as a flasher with timing adjustable to +_ 1 sec. A low leakage timing cap is necessary, at least 10M ohm.
    Leakage will frequently improve with use as C2 did. R1 started out as 10k & R2 a 1M pot. As timing closed in on 3 min. R!-2 replaced with fixed value & lower R pot. Time over 4 hours remained at 1 sec. fast. LED used is 30 mA white piranha, but can be as desired. Three Sec. Pulser 00000.jpg
     
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