Smart, small, versatile, BOBCAT.

Top and bottom view of a soldered BOBCAT device.

Table of contents:

1.) Functionality

2.) Schematic

3.) Bill of material

4.) Gerber files

5.) Firmware

6.) Case

7.) Camera cable

8.) iOS app

Almost every camera has an interface for triggering. A corresponding cable with the side for connection to the camera is manufacturer-specific, whereby the second side is often a 2.5mm jack plug.

The following picture shows the second side of the 2.5mm jack plug:

As you can see in the picture above, connecting FOCUS and SHUTTER to GND is enough to trigger the camera.

In order to trigger or control the whole thing wirelessly, a suitable microcontroller is of course required.

As we can see in the simple circuit, we use a BLE microcontroller U1 (nRF52832) to control the camera and communicate wirelessly with an iPhone or equivalent iOS device.

In addition, we need a jack socket (J1) to carry the trigger cable, a button (U4) to be able to trigger without an iOS device, a battery holder (U2) for the coin cell, a slide switch (U3) to turn the device on and off and a few pins U5 (SWD = Serial Wire Debug) to flash the microcontroller with the firmware.

In order to save space and get a pretty small PCB, it consists of two layers. The BLE microcontroller is on the bottom, while all other components are on the top.

The BLE microcontroller is the only SMD component. All other components are through-hole components.

Here you can download Gerber files for the PCB:

Gerber files

The firmware for the BLE microcontroller nRF52832 from NORDIC SEMICONDUCTOR was written in C++ by using the great Open Source Bluetooth Framework Arduino Core for Adafruit Bluefruit nRF52 Boards.

Here you can download the latest firmware as compressed hex file:

Firmware version 0.9.9

If you want to flash the BLE microcontroller from NORDIC SEMICONDUCTOR you also need the appropriate Soft Device:

S132 nRF52832 6.1.1 Soft Device

There is no need for a bootloader, because currently the device has no USB connector and no OTA (Over The Air) flash functionality. It can only be flashed via SWD (Serial Wire Debug) interface.

You can find the pins for flashing the firmware via SWD on the top side of the PCB. Please take care of the correct pin assignment while flashing the firmware. Otherwise you could damage your device.

The housing consists of a total of three parts: The bottom side where the circuit board sits, the top side with the round hole for the manual trigger button and the optional hot shoe adapter, that can be glued to the bottom side of the case to attach the device to the camera's hot shoe when in use.

Here you can download the latest STL files for the case if you want to 3D print the case for your BOBCAT device:

STL files for the case

In order to trigger your camera you need to find out which cable you have to connect from your camera to your BOBCAT device. The picture below shows a cable from Rollei that can be used for Sony Alpha 7 series cameras.

The BOBCAT iOS App can be downloaded free of charge from the App Store.

After starting the application, the environment is scanned for BOBCAT devices for 10 seconds and the result is sorted by distance:

If you tap on a device in the list, a connection to that device will be established. If there is only one device in the list, the connection will be established automatically after scanning is finished.

As you can see, there a three different modes available for controlling your camera. The single shoot mode is the default mode after a connection is established. If you press the button, your camera shutter gets triggered and exposed as long as you hold the button down (you have to set your camera to BULB mode before):

The second mode is the interval mode, where you can create complex intervals by selecting pictograms from the menu. A pictogram stands for wait, shoot or a bracket including several pictograms with a number of iterations.

You can reorder the pictograms with drag and drop or delete pictograms by pressing the X button.

And you can also change the parameters for wait, shoot and bracket pictograms.

The third and last mode is the expert mode, where you can easily write your own expressions for your intervals.

Therefor you use the custom keyboard containg all available pictograms and numbers.

The following picture shows an interval, that initially waits for 5 seconds and then shoots with an exposure time of one second, afterwards waits for two seconds and repeats that five times.

You can write very powerful intervals by using nested brackets, multipliers with up to 512 characters.

You can also wait for an absolute time of day, before triggering your camera, as the below picture shows:

After sending your interval to the BOBCAT device you can of course terminate the connection to the device or switch off your iPhone. Your interval will of course be executed reliably.

In Expert Mode you can write expressions with pictograms to trigger your camera with intervals.

There are two action pictogram symbols:

1.) w{number | time of day}

2.) s[number]

The first pictogram is the pictogram for wait. It expects a mandatory number in seconds or a time of day, e.g.:

w0.5

w11:55:00

The second pictogram is the pictogram for shoot. It can have an optional parameter for exposure time in seconds, e.g.:

s

s1.5

The pictograms can be combined and embedded with brackets and an optional multiplier, e.g.:

w5(s1w3)10

This expression initially waits for 5 seconds, then shoots with an exposure time of one second and afterwards waits for 3 seconds before it repeats the shoots for a total of 10 times.

The wait pictograms can also be used with a time of day, e.g.:

w18:00:00(sw3)5

This expression initially waits until 6 p.m., then shoots and afterwards waits for 3 seconds before it repeats the shoots for a total of 5 times.

Expressions can also be nested, e.g.:

(w5(s1w3)10)5

This expression would fire a total of 50 times.

Expressions must have at least one shoot. The following expressions are invalid and will not be sent to your camera:

w1

w11:55:00

w1w2

Expressions will be automatically validated while typing. If your expression is valid, a green checkmark will be displayed. Otherwise a red cross will be shown. If your expression is valid, then the number of shoots will be shown right to the green checkmark and the button to send the expression to the BOBCAT device will be enabled.

You can use up to 511 characters for your expression. After your expression was sent to the BOBCAT device, you can disconnect or switch off your smartphone. Your interval will of course be triggered to your camera.