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Hacking a 1-sec accurate timer Answered

Hey all, For my digital SLR camera, I've hacked together a cable relase using a three-way switch. This works a treat, and now it's time to graduate to full automation to help with night time navigation. For this I need to build a timer that keeps a switch in the 'on' position for a certain number of seconds. The timer needs to be accurate to the nearest second, so nothing fancy. Ideally it would be a number pad I can type into the number of seconds. So any ideas? I'm putting together a short instructable to make the cable release. Cheers, Pierre

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eKstreme
eKstreme

12 years ago

Thanks for the suggestions everyone. I looked at 555 timers and I think one called the MK111 from Maplin here in the UK will do. The output should not be powered, so I'm hoping to find one with relay output to trigger the contact for the required length of time. I don't mind if the timer itself needs power as long as the power is easily provided by a pair of batteries. Forgot to mention: this will be for night-time photography. Pierre

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NachoMahma
NachoMahma

Reply 12 years ago

. The 5A contacts should handle anything a camera will throw at them.
. The max 5s pulse time might be too short for low-light photos - I'd try to find >= 30s. Wiring it up "backwards" (use NC contacts) will give you one minute exposures, but only 5 secs between shots.
. If you plan on leaving it unattended for very long, you might want to look for something with uses less than 100mA. Depends on how big your battery is.
. IIRC, that's about 10 $US. I'd pay that for one. The components alone are worth close to that.
.
. Next time, include a link so I don't have to search for it - I'm lazy.

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NachoMahma
NachoMahma

12 years ago

. Sounds like a job for a 555 timer. Several projects here on Ibles; thousands on the 'Net.

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Patrick Pending
Patrick Pending

Reply 12 years ago

That's definitely the easiest way. You can either use a potentiometer to vary the time period or use a rotary switch to select different RC combinations to give preset times. Cheers, Pat. Pending

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Goodhart
Goodhart

12 years ago

The LS7213 is a CMOS silicon gate delay timer IC that incorporates four operating modes and eight time delay ranges. The time delay ranges are configured to produce real-time delays when the input time-base frequency is kept within 10 kHz to 1 kHz. Features include an ac oscillator port for time-base generation and complementary delay outputs with an option to "flash" one output as a delay-in progress indicator. Delays are initiated by a trigger and can be aborted by a reset. The LS7213 is a 14-pin DIP and LS7213-S is packaged as a 14-pin SOIC.

But, come to think of it, the 555 would be the easiest choice, and if you need low power consumption, there is always the CMOS version of the 555The Link to the LMC555 pin to pin compatible to the LM555