This intervalometer has the following features:
- Intervalometer mode with options to change delay time and exposure time
- Sensor mode with built in light sensor and connector for external sensor input
- Manual mode allows intervalometer to act like a simple remote cable
- Integrated 2x12 LCD display
- Fully optically isolated interface to camera
- Total package is roughly 1" x 2.5" x 3" finished
- Electronics small enough to fit in a mint box
- Source code is available for download so that you can change programming as desired
- Available as a kit from www.ottercreekdesign.com
Step 1: Schematic
Below is the schematic for the project.
Step 2: Gather Materials
|1||2 position tact|
|3||500 ohm resistor|
|4||1k ohm resistor|
|2||1uF tant cap|
Most of the parts are available from Digikey - except the case (Polycase.com) and the LCD (crystalfontz.com). I've pulled all the parts together into a kit that's available for purchase at Otter Creek Design (www.ottercreekdesign.com) or Amazon.com (www.amazon.com/dp/B002POLY3Q).
Additionally, if you want to modify the program and download to the device, you'll need an Atmel ISP. I use the AVR ISP from Atmel, although there's a lot of different choices out there. The part number on Digikey is ATAVRISP2-ND.
To modify the program, you'll want to download WinAVR and AVR Studio - they're both available at no cost. WinAVR is available from SourceForge, AVR Studio is available from Atmel. Both programs are required as you'll need AVR Studio to program the unit, and WinAVR for the avr-gcc program - since the source is written in C. Source is available in the download section of www.ottercreekdesign.com website.
Step 3: Solder Parts on the Back of the Board
Solder parts on the back of the board first.
Start with the processor. The best way to solder the processor is to first add a bit of solder to the pad at pin 1 on the board. Next place the part over the solder pads and align it horizontally and vertically. Once all the pads and pins match, touch the soldering iron to pin one. This will melt the solder thats on the pad and hold the processor in place.
Check alignment again - it must be fairly precise. Next, touch the soldering iron to pad 16, heat it, and feed a small bit of solder. Now that two corners are attached, work your way around the processor soldering each pin. If you end up with solder balls (bridges between pins), see step 5 of this instructable - it gives some tips in how to fix this problem.
Next solder the DAC (u5) in place. Use the same technique as you used on the processor - apply solder to one pad, align, fix, and then solder the rest of the pins.
The power regulator is the next part. Note that the power regulator and the DAC look identical. The packaging for the voltage regulator will be marked with a 'V' and the DAC will have a 'D'. If they're not in their packaging, the DAC is marked with the letters ADMW.
After the power regulator is soldered, we'll finish the power supply part of the board. Solder C2 next - it's the ceramic 470 pf capacitor. Install C1 and C5, they're 1 uf tantalum capacitors. Note that C2 does not have any orientation requirements, but C1 and C5 do have to be placed with the stripe on the positive side of the power supply. You'll see '+' signs under the solder mask - align the stripes on the caps with the '+' signs.
The resistors are next. There is no orientation requirements for the resistors, they can go on any direction.
Solder on R1 and R2. They're the 2k ohm terminating resistors for the serial network. Same procedure, put solder on one pad, place the part, align, melt, and then solder the other side.
Solder R3,R4,R5 in the middle of the board. These are 1k ohm current limiting resistors.
Now you'll want to solder the optoisolator onto the board. You'll need to be careful with the orientation of this part. In the picture below, you'll see pin 1 in the upper-left corner of the white part. It's denoted with a small circle under the solder mask. On the optoisolator, you'll notice that one edge is beveled. The beveled side is the same side that has pin 1, so put the beveled side on the left. Solder the part using the same technique we've been using.
Place the 6 pin programming header into the board and flip it over to solder. The header should face the back of the board, but needs to be soldered from the front side. Heat each pin until you get good flow of solder into the joint.
Place the 2.5mm jack into the board and again flip it over to solder. There's 4 pins that must be soldered.
Finally, solder the phototransistor in place. The leads on the phototransistor must be bent 90 degrees. First, feed the leads of the transistor through the board and make sure the flat edge matches the picture in the silkscreen on the other side of the board. Once it's correctly aligned, bend the leads 90 degrees about 3mm from the base of the phototransistor. Solder the part in place.
Step 4: Solder Parts on the Front of the Board
The front side of the board is much easier than the back.
Start with the resistors. There's 5 on this side of the board. R8, R9, and R10 are 500 ohm, R6 is 1k ohm, and R7 is 10k ohm. Solder them as usual - put solder on one pad, place the resisitor, heat the pad, and then solder the other end of the resistor.
Next place the capacitors. C3 and C4 are 0.1uf bypass capacitors. They're not orientation specific, so they can be soldered on to the board either way.
Place the two-position tact button onto the board. There's two alignment pins in the back of the switch that will fit into two holes in the board. Hold the switch in place and solder the tabs on all four corners into place.
Solder the final 3 tact switches into place. These do not have alignment tabs, so must be aligned over the pads, held, and soldered into place. There is no orientation concerns with these parts.
Step 5: Ouch, I've Got Solder Balls
When soldering fine pitch parts, it's inevitable to get what's called solder balls. These are bits of solder that bridge between pins of the part, and refuse to go away. I've got a simple solution to the problem.
Note on the first image, a solder bridge between the three left-most pins on the bottom of the part. I've tried solder braid, xacto knifes, etc, to remove this type of problem, but haven't had much luck. Here's how I do it now.
Lay the soldering iron across the pins as shown in the second picture. Once the solders melted, tap the edge of the board on your workbench rather firmly. The first tap is shown in picture three - the solder ball is gone from the 3rd pin, but is still bridging the 1st and second. So, heat the pins up again, tap again, and the result is shown in picture four.
Note in picture 4, the solder has mostly moved from the pins and is spread across the solder mask on the front of the board. I cleaned this up by first removing the tail of solder, and then heating the pins again (with a clean tip) to get the results in picture 5 - a perfect solder job.
Step 6: Connect Board to LCD Screen
The intervalometer board connects to the LCD module with 11 pins - broken into a 5 pin and 6 pin header.
First, install the headers into the intervalometer board. They should be installed on the front of the board (soldered on the back) such that the pins extend up from the front of the board.
Once the headers are installed in the board, place the LCD module over the pins. Again, just to be sure, the LCD module is mounted on top of the intervalometer board, not behind it. On some LCD modules, the locking tabs for the LCD shroud may be in the way slightly and prevent the LCD from seating all the way down onto the intervalometer board. If this is the case, bend the tabs slightly so that they do not interfere.
Complete all the solder connections on the headers.
Now it's time to install the red LED. The thin part of the front of this LED protrudes through the case, so it needs to be mounted fairly high. Mount it such that the shoulder that's below the thin part is even with the front of the LCD screen. When inserting the LED, make sure the long lead is on the rounded side of the silkscreen and the short lead is on the flat side.
Step 7: Finishing Touches on the Board
A couple last things.
First, we need to wire in the power switch. Strip and tin both ends of the 2 conductor ribbon cable. Push the two wires through the back side of the board and solder on the front side. Once final the board is fitted into the case, the other end of these wires will be soldered to the power switch.
Now, install the battery holder. Make sure the positive terminal of the battery holder is in the correct position. Flip the board over and solder the pins into place.
Step 8: Case Assembly
The board attaches to the front panel of the case with 5 screws.
Feed 4-40 screws through all 5 screw holes. Slide a 5mm spacer onto each screw. Add an additional 3mm spacer to the single screw on the bottom of the case front.
Clip the leads on the 4 LEDs and place them into the button holes in the case. Note, from now on, you need to keep the case face-down, or the LED's will fall out. Once the board is secured, the LED's will be captured and stay in place.
Mate the board and the case. The critical part here is to go SLOW. Place the board/LCD into the case so that the nuts on the top screws are behind the LCD and the screws are sitting loosely in the 1/2 moon cutouts in the LCD board.
Now, feed the middle screws through the board and LCD - you'll need to screw them in - the space is tight on purpose so that the screws engage in the boards as they pass through. Tighten these two screws slowly, alternating back and forth so the board/LCD comes down even. Be careful that the pushbuttons (LED's) don't fall out, and make sure the red LED goes into it's hole. As the board comes down, make sure the single screw at the bottom of the case goes through the hole in the board.
Once the center screws are snug (do NOT overtighten), check the whole unit for alignment. Before things are tightened, it's possible to push it around so that it lines up square and straight. Put a nut on the single screw, and tighten it. Finally, hold the upper screws into the 1/2 moon cutouts in the LCD, and tighten these as well.
Now, there's a bit more soldering to do.
First, strip about 1" from the end of the 2' cable. Strip each wire about 1/8". Tin both wires and the shield wire. Put a small 'L' in the end of the shield wire. Solder the wires to the board as shown in the picture below. Use the tie-wrap to attach the wire to the board assembly. This will act as a strain relief. Feed the wire through the hole in the bottom of the case.
Feed the power wire through the switch hole in the side of the case. Solder a wire on each tab of the power switch. Insert the power switch into the case.
Now, you're ready to close the case. The trick here is that you have to rotate the case lid into position. Put the top on the case at an angle such that the phototransistor and 2.5mm connector are aligned with their holes in the case. Push down and rotate the case lid such that the pt and connector push into position and the case lid shuts cleanly onto the case. Install the 4 case screws.
Finally, the 2.5mm stereo plug must be soldered onto the cable. The very first thing you need to do is slide the plug cover onto the cable. I'm not going to tell you the number of times I've soldered something twice because I forgot this step.
The wiring of the plug is simple. The shield goes to the clip, the black goes to the tip, and the red goes to the middle band. This means if you're looking at the plug - with the strain relief on the left and the tip on the right, you should land the wires Shield, Black, Red.
A tip here: The chrome coating on the plug is nearly impossible to get solder to stick. Take some sandpaper and rough up each solder point - there's brass underneath the chrome - sand until you see the brass and your connections will be much stronger.
Once the wires are soldered, crimp the strain relief and slide the cover over the plug, screwing it in place to secure.
Step 9: Interface Cables
The intervalometer plug is wired for direct connection to a Canon Rebel series camera. It has a standard E3 connector (2.5mm plug).
In order to connect to other cameras, you'll need to make a cable that converts from the E3 plug to whatever plug your camera uses. I've been most successful doing this by purchasing simple remote switches for other cameras, chopping off the switch part, and adding a 2.5mm socket to the end - so that it can be plugged into the intervalometer.
Below are some pictures of the various cables I've built.
www.amazon.com/dp/B002V63TC2 Canon E3 to Canon N3 cable
www.amazon.com/dp/B002V641LK Canon E3 to Nikon D80/D90 cable
www.amazon.com/dp/B002V6BET2 Canon E3 to Nikon D700/D300 cable
Step 10: Intervalometer Operation
Up - move backwards in the menu structure, or if at item level, increase value.
Down - Move forewards in the menu structure, or if at item level, decrease value.
Enter/Sel - Select the current menu item, or at item level, change value.
Trigger - Trigger is used to initiate each function. When Interval, Sensor, or Manual are selected, Trigger causes the unit to execute the function based on the settings that were made to the unit. For instance, in Sensor mode, once the edge is chosen and the threshold is selected, pressing Trigger will cause the CT-1 to start looking at the sensor input and triggering the camera based on the current readings. In Setup mode, the Trigger button has no function.
The menu structure is shown below. There's four main menu items:
Interval - Intervalometer functions. Set exposure and delay and take a series of pictures.
Sensor - Use the built-in phototransistor to detect changes in lighting and take pictures
Manual - Use the unit as a simple remote device
Setup - Setup functions
The interval menu is use to access and set the exposure and delay timers for the unit. Items in this menu are:
- DlyUnits - This sets the units of measure for the delay portion of the intervalometer - either seconds or minutes.
- Delay - Amount of time for the delay, of course based on DlyUnits.
- ExpUnits - Exposure units (min/sec)
- Expose - Amount of time for the exposure - in ExpUnits.
Note: Generally exposure is controlled on the camera, so 0.2 second exposure time (default) is sufficient to trigger the camera. If exposure control from the CT-1 is desired, the camera must be in bulb exposure mode.
Note: Autofocus should probably be OFF on the camera. The CT-1 will turn on the focus output to the camera, but in general if Autofocus is On in the camera, you'll have two undesired effects. First, the camera will take a long time to set focus, potentially missing the exposure. Second, each frame taken in the sequence will potentially have a different focus point.
The sensor menu allows use of either the built-in photo (light) sensor, or an external sensor that is plugged into the 2.5mm sensor input on the side of the unit. Items in this menu are:
- SensVal - Current value of the sensor input. This is an analog input channel that ranges from 0 to 255. Not changable - expect of course by changing the light hitting the sensor.
- Edge - Lets you select the edge that will cause the unit to trigger. Choices are Rise and Fall.
- Thrshld - This is the threshold value - it sets the sensitivity of the unit. When the SensVal crosses the Thrshld value in the Edge direction, the camera will be triggered.
Example: Say your camera is set up such that it's in the sun, and you want to take a picture when a shadow obscures the sun. In direct sun, you see that SensVal is 240. When you block the sun, SensVal drops to 100. In order to set up the unit, you'd want to set the Edge to Fall (we want to take the picture at the moment that the sun is blocked), and set Thrshld to around 200. This way, when the sun is blocked, SensVal will drop from 240 to 100, and as it passes 200, a picture will be taken.
Note: For sensor mode, Autofocus should be disabled as it will generally cause a delay in taking the picture, likely missing the event that you wish to capture.
Note: Consider using Mirror lockup when in sensor mode (see the setup menu).
The manual menu allows two options that make the CT-1 more like a simple switch trigger.
- Remote - Choose this mode and when you press the trigger button, it acts like a simple remote. Press the Trigger button 1/2 way, it focuses, press it all the way to take a picture.
- BulbTogl - This mode toggles the camera output. When first initiated, press the Trigger button 1/2 way, and the camera will focus, press the Trigger completely, and the camera shutter will open. Press the Trigger again, and the shutter will close. The camera must be in bulb mode for this function to work correctly.
- MirrorLU - Use this option to set mirror lockup mode on or off in the CT-1. Note that you need to turn mirror lockup on or off accordingly in the camera to match the CT-1 setting. Mirror lockup allows the camera to work in two stages. Stage 1 is to lock up the mirror, stage two is to open the shutter. Normally these stages happen concurrently. With mirror lockup mode, they happen separately. There's a couple uses for this mode:
- Long-distance shots where the mirror movement will affect the stability of the shot
- Capturing events that happen very quickly - eliminating the mirror movement speeds the camera's response.
- FocMaint - Tells CT-1 whether to maintain the focus output to the camera during intervalometer or sensor mode. Since it's recommended that Autofocus be turned off during these functions, FocMaint should generally be set to Off.
- ClkAdj - Allows you to make small adjustments to the system clock. In general it's accurate enough for most work, but if you need more precision, this is the place to set it.
- Contrast - Sets the contrast of the LCD screen.
- BkLight - Sets the backlight mode. Choices are On, Off, and 15 seconds.