More questions on remote control of cameras

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Helped by comments from posters to this newsgroup, I have made three Jaycar
flexitimers to switch on InfraRed remote controls to cause Canon G2 cameras
to take one exposure every ten seconds. . They are made by butchering cheap
I.R. remote controllers from Hong Kong (ebay) and having the flexitimer
relay close the appropriate switch.
They work well.
They are also a bit of overkill. 12Volts to activate  a solenoid to switch a
milliamp or two at three volts maximum.
There must be a simpler way.
A long time ago I built, from a circuit in E.A. (I think) a timer to switch
on and off an EPROM eraser. It had a 555 and a few other bits and the timed
intervals were adjustable.
There must be a similar circuit somewhere to do exactly what I want, which
is to close a circuit so that the I.R. is activated, (always for one second)
and then turned off  for ten seconds. I believe it  would not need a relay
because the device being switched has such low current.In other words, I
believe the switching transistor would be able to handle that sort of
current and voltage.
The ability to alter the off time from, say, six seconds to twenty seconds
would be an added bonus.
Can anyone point me in the right direction?



Re: More questions on remote control of cameras

"L.A.T."
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**  If you drive a few mA into the base of a BC547 or similar  -  the
collector to emitter resistance falls to a low value and will act as an on
switch.

An LM555 will operate from 5 volts DC, so a 2.2kohms resistor from pin 3 to
the base will do.

Up to you to work out the rest as we have no details on those RC units.


.....   Phil



Re: More questions on remote control of cameras

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Re: More questions on remote control of cameras
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The simplest option (from a component point of view) is an 8 pin
PICAXE chip.
http://www.rev-ed.co.uk/picaxe /

Probably no need for any other components as the output pin could be
configured as an open collector (switching between output LOW and
input if needed) that could likely be connected directly across your
IR remote switch.

The PICAXE works down to 3V, so you could probably power the IR remote
and PICAXE from the same battery supply.

A DIP switch on the other pins could select the desired time period if
needed.

No real software skills needed either, PICAXE's can be programmed with
flowcharts if desired.

Silicon Chip have published countless articles on using the PICAXE.

Dave.

Re: More questions on remote control of cameras
finger to keyboard and composed:

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There is a 3V version of the LM555, eg the TLC555:
http://focus.ti.com/lit/ds/symlink/tlc555.pdf

Depending on how the IR remote's contacts are wired, you may be able
to switch them directly from pin 3 of the 555, or via an inverting
transistor, or you may need a CMOS analogue switch, eg CD4066 or one
of the many modern alternatives.

See http://www.maxim-ic.com/appnotes.cfm/appnote_number/638

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Re: More questions on remote control of cameras
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what happens if you short-circuit the remote button and switch the
power to the remote on and off ?


if that doesn't do anything useful here's some other ideas.


use the 555 to drive a mosfet power the whole lot from one of those 9v
batteries,

  +9V--.        |------->  to remote
       |       ||  mosfet
      555 -----'|---+--->  to remote
       |            |
   0V--+------------+

 you probably won't be able to power the 555 and the remote from the
same supply


 or you could try wiring a LDR across the remote contacts and
 blinking a LED at it. (wrap both components in black lightproof tape)
 then you may be able share the supply
 
 (or a phototrasistor based optocoupler may work instead of the LED+LDR)

 given that the remote wants a 3v supply a TLC555 may be a suitable
 timer for these options (as they are isolated you can share the supply)

Bye.
   Jasen

Re: More questions on remote control of cameras

"snip>
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That was one of the things I tried. It seems that the transmitter must be
powered up all the time.



Re: More questions on remote control of cameras
IS this any use?
http://cgi.ebay.com.au/Universal-Remote-Control-Digital-DSLR-for-Nikon-Canon_W0QQitemZ200248997410QQihZ010QQcategoryZ27432QQssPageNameZWDVWQQrdZ1QQcmdZViewItem



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Re: More questions on remote control of cameras

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http://cgi.ebay.com.au/Universal-Remote-Control-Digital-DSLR-for-Nikon-Canon_W0QQitemZ200248997410QQihZ010QQcategoryZ27432QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
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This is pretty much what I am doing. I bought half a dozen similar devices
for $1.90 each. They have a little circuit board with a chip and a couple of
components and membrane switches to select which function the chip will
perform. I take off the membrane and cut a track or two and solder a couple
of wires so that the picaxe acts as a timer and then as a switch.If I can
find out what the pulses the on-board chip generates, I can do away withe
the circuit board and have the picaxe generate the pulses. Then the whole
thing will fit into a Dick Smith switched battery-holder together with its
batteries



Re: More questions on remote control of cameras
I'd be inclined to tackle the problem differently.
I would record the code from a remote control device that actually
works and then reproduce this waveform.

To record the waveform I would use an IR decoder as an input to an
Atmel or PIC.
I would set the inbuilt timer to interrupt every millisecond.
On every interrupt I would compare the state of the input (0 or 1) to
it's previous state.
When there is a change in state, I would save the state and time in ms
to memory.
You don't really need to save the state as you know it will be
inverted every transition.
As a guideline, the RC5 code is 14 bits so there would be about 28
transitions to record.
The total time for the code is approximately 25,000 ms so you would
need to store 2 bytes for each transition.
The millisecond counter would be set to zero on the very first
transition.

Allow about a second from the last transition and then transmit this
information back to a PC via an RS-232 cable.

With this information you can reproduce the waveform.

You would probably gate this with a 36khz square wave and drive an IR
LED with it.
Or you can create these in you microprocessor chip.
That way you can use you PC to send commands to the PIC which then
sends commands to your camera.

Once you suss out the control waveforms you can control the camera at
will.

Hope this helps.


Re: More questions on remote control of cameras
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this gives upto 1ms jitter so the signal rate had better be well below
that...

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it might be a better move to set up an interrupt on the change-of
state of the input pin and use input capture to snapshot the clocks
accumulator, that way you get much better precision in your timestamps
for the signal edges.

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25 seconds?     - seems kind of long!

25 miliseconds? - you'll not detect 28 edges if you sample every
millisecond

250 miliseconds is believable,

--

Bye.
   Jasen

Re: More questions on remote control of cameras
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----------------------------------
You're right.
The timings I quoted were incorrect.  I was just answering without
digging out my code and checking it.
My actual project was a bit different.  I knew my codes and timing and
just sampled the centre of each bit to see if it was a 1 or 0
The correct timing and more info on IR codes can be found on the web
by googling "RC5 Remote Control"

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