This project marks the fifth variant of the CamMan family of camera control chips. In this release we introduce a special PIC microcontroller that is used to interface nearly any lightweight digital camera to the HobbyZone brand radio control (R/C) model airplanes.
It is important to note that this release is specifically designed for the HobbyZone R/C systems that has their special X-Port™ connector. It is not compatible with standard R/C radio gear (the other published versions of CamMan handles those applications just fine).
Here are the main features of the CamMan-XP camera control board:
a little background. HobbyZone sells several different R/C model airplanes
that are ready-to-fly. The larger models, that are suitable for R/C aerial
photography, are the
Aerobird Xtreme. But, they all use proprietary radio control
equipment that does not allow us to plug in standard R/C accessories.
But CamMan-XP changes all of that. It connects to the HobbyZone X-Port connector. This port is a 4-pin connector found on the bottom of the fuselage. It is normally used for their combat and bomb drop module, but we are going to use it to take photos from a digital camera. The camera's shutter will be activated from the stock HobbyZone R/C transmitter.
The basic modifications center around a simple circuit that uses a microcontroller to decode the X-Port signal to activate the camera's shutter. In its most basic configuration, only eleven parts are needed. But as simple as it all sounds, this isn't a project for an entry level electronic tech. Do NOT attempt this project unless you are familiar with reading schematics and have soldering experience.
What Digital Camera Can I Use?
Choosing a digital camera is really up to you. It just needs to be lightweight so that the HobbyZone model airplane can safely fly with it attached. I suggest you keep the camera weight well under four ounces.
I really like the Aiptek Mini PenCam 1.3 and the Mustek G-Smart Mini-3. Both weigh a couple of ounces and have good resolution for A/P (aerial photography) use. In fact, our original CamMan project supported these cameras and they performed very well.
A unique feature of CamMan-XP is that it can snap photos using two totally different methods. It provides an electronic shutter switch AND a mechanical shutter method that uses a standard micro sized R/C servo. The electronic connection method is preferred and involves opening up the camera and soldering two wires across the shutter switch. However, if you are not interested in voiding the camera warranty, then just mount a servo on the camera's housing and have it act as the finger press. A good servo choice is the tiny 6-gram Hitec 50.
But unlike the other CamMan Projects, we will not get into how to hack the camera. We've covered the basics in the other projects and some of the R/C hobby forums have had discussions about hacking cameras too. So, there is really no need to repeat that information here. But, if you need advice, just post your questions on the RC-CAM forum and someone will help out.
Tricks for Kicks
There are other clever features built into the CamMan-XP control board. Some are useful even if you don't want to take aerial photos.
How would like to add a Lost Model Finder? Or, how about an
on/off control output that can be used to remotely turn on some night flying
LED's on your model? Well, CamMan-XP has you covered. These features are
handy enough that you may want to build the project just to use them all
on their own.
PIC Chip: The little 8-Pin Miracle
CamMan-XP is based on a tiny 8-Pin chip. It is a MicroChip Technologies PIC12F629 microcontroller that uses custom firmware that you can download for personal use at no-charge. Even though a microcontroller is used, cost is very low. You can build the entire CamMan-XP interface circuit for under $20. Total parts count is minimal and the assembled circuit weighs just a few grams.
Let's take a quick tour of the various signals on the PIC chip:
The PIC12F629 PIC is a "Flash" part, so it can be re-programmed hundreds of times. This allows for cheap software upgrades since the same part can be used.
Be sure to properly select the PIC's configuration fuses before chip flashing. They should be automatically set by the hex file, but it is always a good idea to verify them. These fuses are managed by special settings within your chip programmer's menus.
For example, the screen shot on the right (click for larger view) shows how they may appear in your hobby grade flash tool. The required fuse settings are summarized below:
Warning: If your chip programmer asks if you wish to use the OSC CAL value from the hex file, then be sure to click the response that leaves the value alone. If you use the data from the file it will over-write the factory stored CAL data and the PIC will be rendered useless! You should also read this: OSC cal data corruption work-around.
The required firmware (hex file) that is needed to flash-program the PIC is provided at no charge for their own personal/hobby use. This means that a R/C hobbyist can install the firmware into their PIC, license-free. You are NOT granted permission to do this task for others and you cannot sell the project. In other words, you cannot offer a pre-programmed PIC or a finished product (exceptions require written permission from us). Sorry, but the text based source code is NOT available.
X-Port Connector X-Posed
The HobbyZone X-Port is a four pin connection. It is a proprietary design that is NOT compatible with standard R/C equipment. This is too bad since it really limits what the average fellow can connect to the model.
The basic X-Port signal is PRM (pulse rate modulated), whereas a standard R/C servos is PWM (pulse width modulated). The PIC's job is to decode the variable pulse rate and use it to determine when the pilot has commanded the X-Port feature.
The CamMan-XP design includes a 5.0VDC VReg (voltage regulator) because the X-Port's native voltage (7.2VDC) is too high for direct use by the PIC. The VReg is also a handy source for camera power, assuming your camera is compatible with 5.0VDC. The chosen VReg is a LM2940 low drop out type; a common LM7805 will NOT work well in this battery powered application.
There's More to Soldering Than Solder
For sure, this project is not for beginners. But if you can read a schematic, and have experience building electronic circuits, then this project is perfect for you.
Everyone has their own way of building prototype circuits. So, I'm not going to offer detailed instructions on how to solder up the CamMan-XP camera controller. Instead, I will show what mine looks like and let you decide how you will attack yours. Just keep in mind that it needs to be rugged for use on a model airplane.
I used a 1.1" x 1.5" piece of phenolic perfboard for my project. The photo on the left shows the finished board. It does not include the Lost Model Finder or the on/off control components. But there is room for them too.
The 2-pin connector is for electronic shutter control and the 3-pin is for the alternate camera shutter servo method. The 5V VReg will need a heatsink if used to power a camera that draws more than a couple hundred milliamps. If yours runs too hot after a few minutes of use then add a heatsink!
The wiring for the X-Port connection requires three conductors: Pin 1 (Bat+), Pin 3 (X-Port Sig), and Pin 4 (Bat Gnd). Be sure to confirm the battery polarity on the model's X-Port connector. Getting it wrong will result in a smoky disaster. By the way, the materials list includes the part number to a nice 4-pin connector that fits the X-Port like a glove.
Before going further you should stop and double check your work.
Controlling the camera shutter can utilize the servo controlled method or the electronic switch output. The latter is the best way, but requires taking the camera apart and soldering to the shutter switch contacts. It will reliably interface with an active high or active low type camera shutter design. Just use your voltmeter and identify which shutter switch contact is most negative. Connect this to J4 pin-2. The positive side of the shutter switch goes to J4 pin-1.
You can test your shutter wiring out by pressing the S1 switch. Each press will snap a photo. If it doesn't then something is wrong.
If you are using a camera that goes to sleep (shuts off) when unattended, then you can program CamMan-XP to periodically take a "keep-awake" photo. The settings are stored in the PIC's E²Prom memory, but you can change them as often as you would like. Just follow these instructions:
Stand-Alone Camera Feature:
You do not need to connect CamMan-XP to a HobbyZone X-Port. You can just apply 5V to 9V power to J1-1 and J1-4. Even with the X-Port signal unconnected, the camera will still take photos at whatever interval you programmed into it (see keep-awake programming section). This is a convenient (and generic) way to take photos in the air or around the home.
The technical details are available as file downloads. There is no charge for the firmware hex file when used in a personal hobby project. Commercial users and resellers must obtain written approval before use (license permission). More details about this are in the readme.pdf file.
Please be aware that the information is copyright protected, so you are not authorized to republish it, distribute it, or sell it, in any form. If you wish to share it, please do so only by providing a link to the RC-CAM site. You are granted permission to post links to the web site's main page (http://www.rc-cam.com/). Please respect this simple request.
The Small Print:
All information is provided as-is. I do not offer any warranty on its suitability. That means that if you build and use this device, you will do so at your own risk. If you find software bugs then please report them to me. I can only make corrections if I can replicate the bugs, so please give me enough details to allow me to witness the trouble.
I would enjoy hearing
from anyone that uses the CamMan-XP system.