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The Projects Forum Working on an electronics project and would like some suggestions, help or critiques? If you would like to comment or assist others with their projects, this is the place to do it.

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Old 09-12-2007, 08:13 PM
bobank bobank is offline
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Default 10 sec. countdown timer with LED display

Is any simple circuit available for countdown timer to start from no more than 10 sec ( can start as low as 3 second and go down.) On 0:00 sec relay activates, It should be able to use 7 segments display. What I want to make is something like clap board for movie clips for sinhronizing cameras. ON flip of a switch, red display start from, let's say 3:00 SECONDS, When it comes to 0:00 secs, relay should be activated, on relay I could connect LED light so something will get both cameras visible signal for first frame. It can work without LED light and relay, but it is easier to notice light than read numbers. Thanks
Boban Klasnikov
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Old 09-12-2007, 09:23 PM
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cumesoftware cumesoftware is offline
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Is it for a bomb? Just kidding.

You can resort to a variety of TTL or CMOS chips, depending on what you wan't, or a PIC microcontroller instead. So, what tecnology do you have in mind?

Please give more details about this project. What are the requirements?
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Old 09-12-2007, 09:42 PM
bobank bobank is offline
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No reqirements, just something to work. My skills in elecronics are the best when:
1. I come into the store and buy product, and/or,
2. get schematic and do soldering ( pretty good in that)
Plus, my free time is unlimited. I bought myself about 10,000.00 dollars electronic laboratory and all I do was to turn on air solder station when is cold in the winter. So, you can guess I live in US. All time spent working so I can afford to buy things that I will never use because I have to work.. That was long answer. The sort is: something that have red numbers and they go down till 0.
Thanks, boban
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Old 09-14-2007, 11:09 PM
Gadget Gadget is offline
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Quote:
Originally Posted by cumesoftware View Post
Is it for a bomb? Just kidding.

You can resort to a variety of TTL or CMOS chips, depending on what you wan't, or a PIC microcontroller instead. So, what tecnology do you have in mind?

Please give more details about this project. What are the requirements?
Bet that comment lit up the board at FBI headquarters...
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Old 09-15-2007, 01:49 PM
mozikluv mozikluv is offline
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Default timer

a cd4510 which is a cmos presettable bcd up/down counter, a cd4511 which is a cmos bcd 7 segment latch decoder and a 555 timer will do for you. plus a couple of transistors to drive your relay

moz
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Old 09-17-2007, 09:25 AM
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I'm guessing if it's for a Clapper Board, your gonna want 100th of a second divisions..... i.e. 10.00 down to 00.00 seconds.
That will require cascaded counters, and probably a slightly more accurate timebase than a 555.
A Micro based solution may be tidier, and more compact.
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