My personal experience with R/C airborne video is focused on wireless video systems that transmit realtime images. However, airborne still photography is quickly becoming a popular alternative, especially since it avoids all the FCC/ham license issues. And the new mega-pixel digital cameras are low cost and are surprisingly small. Nearly any model aircraft can haul one around.
This project introduces CamMan, an 8-pin microcontroller that performs the required magic.The camera that was used in the project is the tiny Aiptek Mini PenCam 1.3. However, other cameras are possible candidates too since the schematics include notes for a universal shutter interface. If you are not using the Aiptek camera then it will be up to YOU to determine how to hack your particular digital camera. Sufficient details are provided to ease the transformation of other camera choices.
The basic modifications center around a simple circuit that uses a microcontroller to decode the R/C "servo" signal, as well as manage the camera interface. In the case of the Aiptek modification, only three parts are needed; an 8-Pin IC, capacitor, and resistor.
But as simple as that sounds, this is NOT a project for an inexperienced electronic tech. Advanced soldering skills are needed due to the fine pitched soldering that is required (most digital cameras are tiny!). If you are not up to the job then please consider the old standby solution -- glue an R/C servo to the camera and have it push the shutter button. This old trick has been used for decades and works well.
But, you will soon see that there is a higher tech method:
PIC Chip: A Camera Man's Best Friend
CamMan is based on a tiny 8-Pin chip. It is actually a MicroChip Technologies PIC12C508 microcontroller that uses custom firmware that you can download at no-charge. The PIC decodes the R/C signal for shutter activation and (optionally) manages the power up state of the camera.
Even though a microcontroller is used, cost is very low. You can build the CamMan circuit for about $10. Total parts count is very low the assembled circuit weighs just a few grams.
There are eight pins on the CamMan PIC chip. They exist as one of three kinds of signals: Power, Digital Input, or Digital Output.
The digital inputs are level sensitive and are said to be logic High when the voltage is > 2.0VDC and logic Low when they are less than 0.5V. Typical designs will use the VCC voltage (pin 1) for a logic highs and GND voltage (pin 8) for lows. The output sink current is 20mA (plenty for our application).
Let's take a quick tour of the various signals on the PIC chip:
Your exact PIC choices have some flexibility. You can use a PIC12C508, PIC12C508A, PIC12C509, and PIC12C509A. Project Update: You can also use the easier to find PIC12F508 or PIC12F509 instead.
The PIC12C50x is not
a "Flash" part, so you will need a traditional
PIC chip programmer to "burn"
the hex file's object code into the microcontroller. Be sure to select the
configuration fuses during chip burning as follows (these are optional settings
within your chip programmer's menus):
The PIC's Hex file is designed to automatically instruct the programming hardware to chose these values. However, it is always a good idea to check them for accuracy. By the way, after you program the PIC your programmer will report a failure if you attempt to verify the PIC again. Do not be alarmed -- everything is OK. Just ignore the "failure." Whatever you do, do NOT program the chip twice!
If you have trouble burning the PIC, then please check your programmer. Whatever the fault, it is not a RC-CAM hex file issue. The most common problem is that the user has forgotten to burn the PIC's four configuration fuses, as mentioned above. More programming information can be found starting here.
The PIC's circuitry is so simple that a circuit board is not needed. All the parts are mounted on the bottom of the PIC chip, using "Dead Bug" construction (just picture a dead bug lying on its back). For this project I recommend a 40 watt or less soldering iron with a temperature controlled tip.
You can use an IC socket if your camera has enough room to accommodate one. However, there isn't enough space inside the Aiptek camera to allow it. My instructions will assume that the socket is not used.
Start by trimming the PIC's leads to about half their normal length. The skinny through-hole portion is simply clipped off. The photo on the left shows the details.
Assembly of the basic PIC circuit is now complete. All that remains is to add it to your camera. As it turns out, the tough work is about to begin.
Camera Power: Ying or Yang?
The examples that I show will focus on the Aiptek Mini PenCam 1.3 digital camera. If yours is a different model then YOU will need to determine the best way to connect it.
There are two Aiptek camera wiring choices that you can use, depending on your application. Page 2 of the schematic set shows the preferred method of powering the camera from the R/C system ("USB Power" method). Page 3 shows how to wire the camera if you wish to use its two internal AAA batteries.
USB Power: Page 2 of the schematic shows how the PIC is wired for R/C supplied power. When you power the camera from the R/C battery pack the total current draw is about 130mA at 4.8VDC. This represents the average current of a typical lightly loaded servo and should not pose a threat to your R/C system. However, some electronic speed controls that use a battery eliminator circuit (BEC) may need to be tested to see that they can handle the extra current draw.
When you remove power from the camera your still photos will be retained, but all AVI videos will be erased. You can save the stored videos by inserting the AAA cells before disconnecting R/C power. If you can handle the extra weight, just leave the AAA cells in at all times and they will take over when the camera is removed from the model.
Internal Battery Power: If you do not want to power the Aiptek camera from the R/C system then the camera's internal AAA batteries can be used instead. Page 3 of the schematic shows how the PIC is wired for this method.
The camera draws about 240mA from the 3V battery supply while active. To prolong battery life the Aiptek automatically shuts off (goes to sleep) after a short period of inactivity. This reduces the current to about 2.5mA. In contrast, the PIC consumes less than 15uA when not in-use, so it will not affect overall battery life. When the PIC is receiving an R/C signal it draws about 1mA, which represents only 0.5% of the camera's nominal operating current. In any case, the PIC is not a burden to the camera's two AAA cells.
The Aiptek's standby/sleep feature complicates matters a bit. If you look at the schematic you will see that two additional PIC connections are needed to manage waking up the camera when it has entered a standby condition. Pin 5 ("Awake" input) of the PIC monitors the camera's power supply and detects if the camera is on or off. Pin 2 ("Wakeup" output) is connected to the Aiptek's mode switch, which as you know must be pressed to turn on the camera.
If the Awake input signal finds zero volts then the camera is turned off (standby). If this is the case then the Wakeup output goes low for a short period before a snapshot is taken. This acts just like a mode switch press. Once power is detected, Pin 3 (Shutter output) goes Low for a short time to take the snapshot. The camera is free to go back to sleep after this little magic dance, which it will do after sixty seconds of inactivity.
As you can see, the internal battery method requires two more camera connections to the PIC. If you use the R/C (USB) power method then the two extra connections are not needed and are left unused.
Micro Surgery: Wiring the Camera
Let's get down to the business of wiring the Aiptek Camera to the CamMan PIC. All of the camera connections use 30 AWG Kynar (wire wrap) or enamel insulated magnet wire. If you use heavier wire then you will invite shorts on the camera's circuit board and will probably have trouble reinstalling the camera case.
Please note: Each assembly photo can be clicked to get a larger view.
Remove the little circuit board that is shown in the photo on the left. It comes off without a fuss. This board is the AVI video memory. Like everything else inside the camera, it is static sensitive. Be sure to use caution as you handle it.
The chart below shows which wires are needed for the two different power schemes. Use 30AWG wire and cut each to 5" long at this point. They will get trimmed when the PIC is added later.
The chart below shows which servo cable wires are needed for the two different power schemes. Use a "Y" style servo cable if you intend to share the R/C throttle channel.
Route the soldered wires per the photo on the left. The exact number of wires that you have will depend on the power scheme you choose (USB or AAA).
Strategically placed pieces of tape will hold the wires so that they are neat and orderly (important when space is cramped). Leave the excess wire length as-is for now. We will trim it to the proper length when the PIC chip is added.
Reinstall the memory
board. Carefully match its connector pins and press it in place. Do NOT force
Trim the all the wires so that they extend about one inch past the bottom of the camera case. This will provide enough slack to ease the mounting of the PIC, which will eventually go into the little area between the two case screw standoffs. Please see the photo on the left for more details.
Do not connect anything to PIC pins 6 and 7 at this time. They can be grounded if you need to use their special features, but that decision will come later.
Push the chip into the space found between the two case standoffs. The legs of the PIC should point towards the camera bottom. The servo cable can make a half wrap around the standoff to help strain relief it. File a grove in the case to allow the servo cable to pass through. Please see the photo (above, left) for details.
Double check your work. Simple mistakes can destroy the camera, R/C gear, and may generally ruin your day. Reinstall the various camera pieces and covers. You are done!
Set Up and Operation:
I will assume that you will be sharing your throttle channel with CamMan. Connect the camera to the R/C receiver's throttle channel and to the servo or ESC (electronic speed control).
Turn on the R/C transmitter and apply receiver power. If you are using the USB power method then you should hear the camera beep when the R/C receiver is turned on.
First you must "Arm" the system. Move the throttle stick to full low stick then give it full up stick (do not cheat -- use FULL deflection on both extremes). CamMan is now armed.
The arming procedure only needs to be done after you apply power to the camera. If you power the camera from the R/C pack (USB method) then arming is needed every time the receiver is turned on. However, if you operate it from the internal AAA cells, or use the USB method in combination with the AAA's, then arming is only required when the batteries are installed. If you want to use the feature on each flight then pop the battery hatch open and close it again before you fly (this will reset power).
You are now ready to shoot photos! If you reduce throttle to below 1/4 stick you should hear the camera beep as it stores a photo. To take another photo you must go above 3/4 stick, then back down again. Practice a bit -- you will quickly see how it works.
If the camera does not take photos then you may have a wiring problem, your stick's trim lever is too offset, or an insufficient ATV mix setting in your R/C transmitter. First you should check your wiring. If it looks good, and the stick's trim lever is centered, then you will need to increase your ATV mix settings (if available) so that they are at 100% or higher. If you are using another channel besides throttle, be sure that its Dual Rates mix is disabled.
If you are using a
spare R/C channel (the gear channel works well) then the operation is nearly
the same. To perform the initial system arming just flick the channel's toggle
switch down then up. From then on you have switch controlled access to shooting
photos. If the switch operation is backwards then either use your transmitter's
channel reversing feature or ground PIC pin 7 (Reverse option).
The technical details are available as file downloads. There is no charge for the information when used in a personal (hobby) project. Commercial users must obtain written approval before use.
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.
If you have technical questions or comments about this project then please post it on the rc-cam project forum.