Hello, I am new to electronics, and so using arduino to get me started.
What I am trying to do is control my Panasonic GF1 using arduino. The remote for these cameras is pretty easy - it has three impedances - no press, half press and full press. So a circuit that will take a photo manually consists of two buttons and three resisters, the buttons bypass resistors to lower the impedence.
While I was testing the manual version, in my mind I was thinking that I could use a transister to bypass the resistor in place of a manual switch... But I don't think this makes sense, there is no current/voltage, so no charge carriers, so nothing to amplify. The camera just seems to measure resistance to work out what to do.
If I want the arduino to change the impedance of the circuit, am I going to need a relay to do it? If so, what kind of relay would I use - an ic?
Thanks for your patience with the newbie question.
If I want the arduino to change the impedance of the circuit, am I going to need a relay to do it? If so, what kind of relay would I use - an ic?
While I'm sure it could be done with transistors and other active and passive components, a lot more circuit details would be needed. If you can perform what you want now manually with just switches then using simple relay contacts to replace the switches is a simple no brains needed solution. I like the following relays because they are cheap, small, and their +5vdc coils can be driven directly from an Arduino digital output pin, no switching transistor required:
Are you sure it really works the way you describe, or was that just your assumption, based on "it could work that way"?
The Canon EOS uses a half-press, full-press system too. There are notes in the Arduino Playground on creating an Arduino based electronic shutter release system for the EOS. Most of what is there would probably also apply to your camera.
As you say you are new to electronics, and as your camera will be a very expensive item, I would be inclined to used relays. They are a bit clumsy, but less easily mis-connected. They will work fine IF, and it is an "IF", merely connection the contacts of your remote control socket to a resistor or switch is all that is needed to simulate "half press", "full press".
The technical details of what you camera needs are almost certainly out there on the web... but be sure to find a RELIABLE answer... several WRONG answers are probably out there, too.
If you can find the techical details of what the camera needs, post a link to them here, and someone will almost certainly chime in with how to make the Arduino deliver what you need.
It would probably also be worth changing the thread title to "Cause Panasonic GF1 to take picture". (You elect to modify the first post in the thread to change the title.)
Are you sure it really works the way you describe, or was that just your assumption, based on "it could work that way"?
No, not an assumption, it does work this way. This was tested in the manual version.
The solution is likely as simple as a pair of 20-cent transistors and a pair of 10-cent resistors. Don't over-think the problem.
Thanks, I needed to check I wasn't thinking in the wrong direction. Using a transister to close the circuit does work, at least, sort of.
I have three resisters in series: 39k - 2.2k - 2.2k
I have a transistor straddling the 39k and another one straddling the 2.2k. If I bring up the transister on the 39k, effectively bypassing it, the overall resistance drops to 2.2k, rather than the 4.4k I was expecting. So something is amiss with my method!
I'll meter it and see what is happening, but otherwise I might post a pic for input.
Here is my arduino layout. Right now, with the transisters in place, and with both pins 7 and 8 low, the resistance between the two lower black and red cables is 30k, rather than 44k expected (the right most resistor of 3 is a 39k, but fritz doesn't have 39k). If I take out the transistors, the resistance is as expected.
I am not sure why the presence of closed transistors would cause the overall resistance to drop?
But can such a circuit work without a common ground reference wired between the Arduino and the remote unit? I can see no way those transistors base connections can conduct without a ground return back to the arduino.
That's one reason why I like relay contacts, no need to worry about voltage levels, or if it's ac or dc voltage, or which direction current is flowing, or having a compatible common reference ground.
I know that a relay would "just work" but I wanted to understand if I can make this work with transistors somehow...
Understood, but to do a proper design one needs to see the complete schematic drawing of the circuit that those red and black wires are interfacing to at the bottom of your diagram, including it's power source.
The details of the circuit within the camera aren't published anywhere as I understand it. So the only knowledge available to the public is that the circuit must start with a resistance of around 40K, when it drops to around 4k the camera will auto focus (half press) and when it drops to around 2k the camera will take a shot (full press).
If I replace the transisters with push buttons (ie, take the arduino out of the picture all together), then it works as expected.
If I don't have the information needed to do a proper design, do I have enough to make some educated guesses (from members of this forum) to do a bodgy design?
In this video, someone has made a motion sensing remote trigger, indeed using relays, the circuit is at 0.28.
If I replace the transisters with push buttons (ie, take the arduino out of the picture all together), then it works as expected.
If I don't have the information needed to do a proper design, do I have enough to make some educated guesses (from members of this forum) to do a bodgy design?
Well if it was my expensive camera, and I had incomplete and missing needed information, but still wanted results I would use relays. What will you actually learn, considering the missing documentation by finding something that haphazardly works? If someone put a gun to my head and said make it work without using relays, I would look at either optical couplers or analog switch ICs.
Sometimes one has to choose which hill they want to die on. This wouldn't be the one for me.
Well if it was my expensive camera, and I had incomplete and missing needed information, but still wanted results I would use relays
Heh. Fair enough. I wouldn't plug this into my camera unless it exhibited the "correct" behavior, which at least is to show that the resistance changes as needed, and with some assurance that I am not inserting current I guess.
In my componant box I have transistors, and no relays, so all I can do is learn from what I have until I can source some.
The combined resistance of the three resistors between the hanging black and red wires is 2.2k + 2.2k + 39k.
Any ideas why with the transistors present with the wiring displayed it would meter at 30k ohms?
Any ideas why with the resistors present with the wiring displayed it would meter at 30k ohms?
Sure, the equivalent parallel resistances of the two transistors wired in parallel with two of the existing resistors when powered by the applied voltage used by your ohm meter.
Sure, the equivalent parallel resistances of the two transistors wired in parallel with two of the existing resistors when powered by the applied voltage used by your ohm meter.
I thought it might be something like that. I figured the transistors would have a far higher resistance.
Does this mean that I can compensate by adding a greater resistance between the transistor legs, to bring the 39k + transistor back to 39k?
Hmm well, interesting. Turns out I was measuring with the polarity reversed. If I measured the correct way, the resistance was normal.
So I grounded the transistor over the 39k resistor to make sure that it was bypassed, which it was. But bizarrly, this also allowed the second transistor to ground even though it is the "wrong" pin.
So it works, and I can now take a photo using a photo resistor going over a threshold as a trigger.
