Some months ago I decided what new camera I will use for my big Hexa. Many many people are using Sony NEX5 cameras for aerial photography. However they a expensive and you need IR Trigger electronics.
I took a look at Samsung NX line and found Jeff Taylor (thanks for the inspiring post) post about triggering them with a simple resistor (not said in that post but I guess you need relays anyway). So I went for it.
I bought a Samsung NX2000 which I must say takes wonderful photos and videos. But Jeff's trigger mechanism did not work in these particular camera. After some trial-error I found that the camera "wants" you to always "focus" before trigger the shutter! No matter the camera setting, believe me!
So what I have. I have an Autopilot that (in relay mode) outputs 5V(APM) or 3.3V(Pixhawk) for a given period of time (shutter time).
With that signal I have to use relays to create two shorts in NX2000 USB pins. One short between FOCUS pin and GND pin and another short between SHUTTER pin and GND pin.
Samsung NX2000 is quite restrictive in how to short those pins. After more trial - error I discovered the following:
- SHUTTER and FOCUS pins cannot be permanently connected one each other. Otherwise, no shutter
- FOCUS has to be shorted to GND some "time" before SHUTTER does. If you short both of them at the same time to GND, you will have a random behaviour. Sometimes it works and sometimes not. This was really annoying as it prevent you to use a double relay to short both pins at the same time
So I decided to built a small circuit to trigger the camera by shorting FOCUS to GND and then (anytime after) SHUTTER to GND
I used what I found at my local electronics store. It maybe done differently!
The circuit for triggering NX2000 receives 5V Vcc, 5V signal (will trigger relays, etc) and GND either from APM or from a 5Vto3.3v level shifter if we use Pixhawk.
Bill of materials:
- 1x NE555
- 1x 1uF capacitor
- 1x 18k resistor
- 1x 10nF capacitor
- 2x double micro relay
The mechanism is as follows. Once the signal goes high (5V), it drives the relay ON. This relay has two lines, the first shorts FOCUS and GND. The second allows 5V vcc to go and feed the NE555 timer.
So we have already provided focus to the camera. Now we only have to trigger the shutter.The amount of time that the NE555 takes to boot up is going to be our FOCUS-SHUTTER delay. It is normally 100ns.
Once the NE555 boot up it always sees a short in it input pin. Therefore it puts its output high what drives the second relay.
Once the second relay is activated, a short is created between SHUTTER and GND.
On this point you should have a nice picture taken in the NX2000!!
One thing left to say. If you come from Pixhwak world you need to convert 3.3v signal to 5V.
I used Marco's circuit in this post.
As you can see all three boards/circuits are connectable/stackable one each other.
Here you can see the full picture:
The FOCUS-SHUTTER delay may have been done with a RC net but I chose NE555 in case a needed to control delay accurately. However I would have needed another NE555.......
For Pixhawk connection I connected it to OUT 5 (as 1 to 4 are configured PWM) and Relay mode.
Some pictures of the process and final result
Everything in a prototype pcb
Already mounted on gimbal with shrinking tube