Trouble triggering a 555 timer

[Jeffrey Warren]

Hey all - electronics folks especially -- Chris Fastie and I have had some trouble getting the 555 timers to work (for triggering 2 cameras at once, for infrared balloon mapping) and I wanted to ask for help or suggestions:

- Chris's timer seems to be blinking properly but not actually switching the relay -- I suspect the battery may not have enough power, not sure current/voltage

- Two of my timers are not switching at all, while the original one I assembled is working fine. I've carefully reviewed every soldering joint and can't see any mistakes. 

You can see more about both issues (including a video of my 3 timers being tested) here:

http://publiclaboratory.org/notes/cfastie/5-2-2012/no-output-signal-ir-kit-timer

Any help or suggestions are appreciated! We are both at wit's end :-)

Jeff

[Randy Sargent]

I tried posting on the page, but don't see it coming through, so I'll reply here too.  (Sorry if I'm just not being patient enough!)

The relay might be a bit of a battery drainer.  Some options:

I think the 555 should be able to directly drive the canon USB trigger, so there may be a way to run the 555 on approx 5 volts, and bypass the relay altogether to greatly reduce the power draw.  If you can post the schematic, I can try suggesting how to mod the circuit.

We use this low-power $15 intervalometer in our timelapse work:  http://www.amazon.com/NEEWER%C2%AE-Timer-Remote-Control-RS-60E3/dp/B003Q9RERY/ref=sr_1_2?ie=UTF8&qid=1335997567&sr=8-2.  It drives a Canon G11 camera directly, or you should be able to modify the cable and add a 5V source to trigger CHDK cameras over USB.

CR123A is a 3V primary cell with serious energy density (over 3 watt-hours in a very light package).  You can stack a few of these to get the voltage you need, but they're very spendy.

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[Chris Stieha]

I agree with Randy. A LM555 timer circuit should be able to trigger
the camera by itself. I thought the Vout on the pulse was the same as
the voltage you put into the chip (minus a little bit, schematic I
found says you put in 5V you get out 3.3V). If it (voltage, current)
isn't enough to trigger it, then you have the output of the LM555
trigger a transistor that allows electricity to flow and press the
button of the camera. You are looking a a couple dollars of parts and
a crazy battery life (6-15 mA, so a 300mAh would last you 20 hours at
the high end)

As for the problems with the relays, unless the relays are bad, I
think you have a very fine solder bridge somewhere. I would run a
multimeter with a connectivity setting (or use the voltage) around
your board. Compare your working one to the one that is not.

[Chris Fastie]

That's great to know that the 555 integrated circuit could trigger the camera almost by itself.  I posted the circuit schematic of the MK111 timer (which has a 555 on it) in the Research Note Jeff linked above (http://publiclaboratory.org/notes/cfastie/5-2-2012/no-output-signal-ir-kit-timer).  Also posted a link to the assembly manual which has the schematic: http://www.velleman.eu/downloads/0/minikits/manuals/manual_mk111.pdf 

Randy, your comment was posted on that Research Note, although I didn't see it until I had already posted another comment. 

My MK111 timer powered by 8 AAA and 3 button cells triggering two Powershots has been taking two synchronous photos every 12 seconds for 1.5 hours. Still clicking...  

Thanks for the help.