SmaTrig - declansator inteligent 15-in-1 pentru camere foto DSLR

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This is the project home page of the SmaTrig 2.1, the improved version of the the SmaTrig 2. On this site you will find complete instructions how to use and build the versatile and compact (27 gram) 15-in-1 camera trigger SmaTrig 2.1. Everything needed to build the device is provided including the PCB design, firmware, drill plans, etc.
The SmaTrig 2.1 is based on an AVR microcontroller, and is equipped with sensor circuitry for detecting sound and light pulses for capturing lightnings or high-speed photography. The 15 functions can be divided into four groups: bulb mode bracketing programs for HDR photography, interval and timer modes, sensor modes and other functions like manual camera triggering or configuration. Many of the modes have some hidden advanced options, but I paid great attention not to obscure their usability. Ritual instruction manual spurners can use the SmaTrig just using their intuition.
The SmaTrig 2.1 controls the camera using a remote release cable, or in a wireless way per IR signal . There is no need to modify the camera in any way to use the trigger. The various sound or light trigger functions use either the integrated photo diode for light detection, or an external microphone that can be plugged into the sensor connector. Flash units can also be connected to the trigger directly to allow high-speed photography.

The features are:

  • variable interval/strobo functions
  • sound and light trigger (rising or falling edge detection)
  • integrated photo-diode
  • lightning trigger (low shutter lag)
  • IR remote control (many camera brands supported)
  • high-speed mode with camera control via IR
  • direct microphone support
  • slave flash trigger with pre-flash suppression (TTL)
  • long exposure (1s - 8h)
  • configuration using EEPROM
  • 3 bulb mode bracketing functions with 3 to 9 shots and an EV step of 1 to 4 for HDR (DRI)
  • all functions of HDR-Jack are included
  • quartz-controlled clock
  • integrated buzzer for acoustic feedback
  • low-power design
  • only budget parts with good availability used

The new features of version 2.1 are

  • direct support of laser pointer for light barrier function
  • additional IR signal for wireless triggering for many functions
  • battery holder allows to change battery without soldering
  • new PCB design for easier and more exact assembly
  • better alignment of programming pads on PCB
  • more consistent function alignment on dial
  • clean up of config function

Trigger modes

The functions of the SmaTrig are devided into two groups. The functions with a black symbol on the label don't need a time specification and are started usually with just one button press. The functions with a red symbol, e.g. intervall or long exposure need a time specifiction. The time is set by pressing the button several times according to this table (printed also on the trigger label):

Presses 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Time 1" 2" 4" 8" 15" 30" 1' 2' 4' 8' 15' 30' 1h 2h 4h 8h

The symbol " stands for seconds, ' for minutes and h for hours. The time is (nearly) doubled at each press. After setting, the time it is beeped back by the trigger for verification. Now you can start the function by another press.

1-3. HDR-modes (bulb mode bracketing)

To overcome the +-2 EV bracketing limit and the 30 s maximum exposure time found in many cameras, the bulb mode can be used to shoot user-controlled bracketing series in a certain range of exposure times. The image series can be used to generate HDR (High Dynamic Range) images. The technique is also called DRI for Dynamic Range Increase. Read the description of the HDR-Jack 2 for more details on the idea. The nominal exposure time of this function ranges between the purely theoretical 1/1000s and 8 minutes, letting you catch the last photon in the scene. The shortest effective exposure time in bulb mode depends on the camera used. Older pre-live-view Canons are the best performers going down to approx. 1/180 s. Newer Canons, Nikons and cameras from other manufacturers range between 1/8 s and 1/2 s. Shooting bracketing series on sunny days with these cameras won't work. Refere to this table to check the minimum bulb exposure time of your camera.
The nominal center times of the bracketing series for the three modes are:

modecenter time
1 1/2 s (* selectable by user, see configuration)
2 2 s
3 8 s

In each mode, 3 to 9 images are shot around the center time, depending on how many times the button has been pressed at start. The number of presses corresponds to the number of 'side images'. One press means 3 images, 2 presses 5 images and so on. The EV step can be selected in the configuration between 1, 2, 3 or 4 EV and is 2 EV by default.
In mode 1, also the center exposure time can also be selected by the user allowing to define a quick-access custom bracketing series.
The bracketing mode supports the mirror lock-up function, as well as the long exposure noise reduction where a dark image is taken internally in the camera after the actual exposure. These optional features are activated by holding down the button for longer time during the last press. The SmaTrig 2.1 beeps every second while the button is held down (up to three times). The beeps correspond to the following options:

# of beepspress durationoption
0 t s normal usage
1 1 s t 2 s mirror lock-up on
2 2 s t 3 s denoising on
3 3 s < t mirror lock-up and denoising on

Of course, the camera settings have to be consistent with the chosen option. The SmaTrig 2.1 can't change any camera options automatically!
For exposures longer than 4 s, the exposure gap is increased automatically by approx. 3 s to allow a quick look on the histogram and abort the bracketing in case of overexposure.
The bracketing can be configured to go from short to long (default) or long to short (e.g. nice for sunrise). There is also the ability to start the bracketed exposure using a cable remote release. The release must connect the ring contact of the sensor port to ground to start the bracketing sequence. This option was meant to use the SmaTrig with automated panorama systems like the Merlin/Orion/Papywizard. Please note that Canon cameras round exposure times 1 s to 1 s in the EXIF data when used on bulb mode The actual exposure times might be shorter.

4. Configuration

In this function, the user steps through a short menu where multiple settings can be made to customise the SmaTrig 2.1. The possible settings and its default values are listed in the documentation available in the download section below. The table also lists which function is affected by which option. Follow the example in the PDF to configure your SmaTrig. All settings are saved in the EEPROM of the AVR permanently. They can be changed any time. The usage of the configuration function is explained below.

5. TTL servo trigger

In this mode the trigger responds to the 2nd flash in the sequence of two flashes as usually generated by TTL-cameras/flashes. The delay between the fist and the second flash must be less than 0.5 sec. This mode is primarily intended for servo flash control, so you will need a cable with a 3.5mm jack plug on one end and a PC sync plug or a big jack for the flash at the other.

6. Sound & light trigger

In this mode, the attached camera or flash unit is triggered by the integrated photo-diode, a microphone, or another external sensor connected to the sensor connector (right, top view). Typical applications of this function are high-speed photography or servo flash triggering.
When there is no plug in the sensor connector, the internal photo diode is used as signal source. The SmaTrig can detect lightnings, flashes, flames, etc.
To use the SmaTrig as a sound trigger, a sound-card-compatible microphone (stereo 3.5mm jack) must be plugged into the sensor port. The power supply is integrated in the trigger.
Two modes of operation are available depending on how often the button was pressed during the activation of the function.
Activation with one press means the trigger is blocked for about one second after firing. A double press means the trigger is permanently "live", there is no dead time. It can be connected to a music signal to trigger a flash to the beat for example.

Continuous operation, no blocking
•• Continuous operation, trigger blocked after firing for 1 s

7. Light barrier trigger

This mode allows to set up a light barrier using a laser (pointer). All you have to do is point the laser beam at the built-in photo diode and press the button. With the barrier you can detect water drops, animals or use it for surveillance purposes. This function has a built-in delay function for water drop photography. Depending on the number of presses at activation the trigger delay will be different. The formula is

delay = (presses-1) / 16 [s]

so for example

# of pressestrigger delay
1 no delay
2 62 ms
3 125 ms
4 188 ms and so on

The steplike delay doesn't replace a complete delay circuit like this, but it allows to adjust the delay by changing the height of the ligth barrier. Immediate firing would result in capturing the drop always at light barrier level.
Please do not point too strong (>5mW) lasers at the photo diode! They can harm your eyes and the photo diode. Be carefull!

8. High-speed trigger

This mode was explicitly designed for high-speed photography. It's a one-shot trigger, meaning that it will deactivate itself after firing to prevent unintended multi-triggering. The self-deactivation is of particular importance when triggering with sound, where falling objects can cause a series of sound peaks after the main triggering event.
Another key feature of this mode is the possibility to control the camera via the integrated IR-LED. The trigger sends out an IR signal after activation (push-button press) and another one after triggering or user (self-)deactivation. This allows you to start the bulb exposure automatically with the trigger and terminate it right after firing. This trick will only work if your camera has an IR sensor which can start and stop the bulb exposure when receiving the IR signal. Nikon and Canon work this way (D60 and 400D at least). This feature only makes sense if taking high-speed images in a dark-room using bulb mode and a flash unit.

The movie explains how to proceed when using this mode.

9. Lightning trigger

Contrary to the popular opinion, it is possible to photograph lightnings by light-triggering the camera directly. If the shutter lag (the delay between lightning detection and exposure start) isn't too long, the results can be fairly good. The lower the shutter lag, the better the results. This trigger mode is similar to the sound and flash trigger mode, but it minimises the shutter lag of the camera. It reduces the lag by keeping the mirror up in a smart way while waiting on the lightning. In case of a detection, the mirror does not need to be lifted before the shutter opens. In the case of the Canon EOS 400D, the pre-release of the mirror reduces the shutter lag by half -- from about 120 ms to 60 ms. Users of non-Canon camras should use Mode 6.

The operation is explained in more detail in the following description. The function is tailored to Canon cameras where the mirror is raised with an extra release pulse and released automatically after 30 s if the shutter-button wasn't pressed for the second time.

  1. The camera is set to mirror lock-up mode by the user and the SmaTrig 2 is in lightning mode.
  2. Push the button multiple times to tell the SmaTrig how long the camera will expose after triggering. This avoids triggering a busy camera or missing a lightning while waiting too long after triggering. Look up the number of presses in the presses/exposure table or the trigger label. After pressing the button the trigger operation starts immediately. The camera is triggered once and the mirror goes up. If a lightning is detected within the next 30 seconds, the camera is triggered for the second time and the exposure starts - a lightning was captured! The exposure "time slot" corresponds to the number of times the button was pushed at activation
  3. After the exposure, the camera is triggered again and the mirror goes up as in step 2. The trigger waits again for a lightning...
  4. If no lightning was detected within 30 seconds the mirror is released automatically by the camera. One second later the camera is triggered by the SmaTrig 2 again and waits for a lightning as in point 2.
  5. Pushing the button again will deactivate the function.

Effectively the camera is waiting for a lightning with a locked-up mirror. The SmaTrig tries to minimise the time where no capture is possible. During the second in which the camera is "reloaded" no lightning can be captured. This results in a theoretical probability of 1/31 of missing a lightning flash.
You can also set the exposure time by holding the button down for longer than 1 s (you'll hear a beep) like in the interval mode. The exposure time is then equal to the holding time. This mode is not limited to capturing lightnings. It can be used whenever a reduced shutter lag is necessary, also with a microphone.

10. Alternating trigger

If you try to capture very rare events like falling meteoroids, or want to shoot lightnings like a pro, this option may be something for you. It allows a 100% interruption-free capturing of events by overlapped exposing using two cameras. The cameras are triggered in a way that each exposure overlaps 1/8 or 12.5% with the previous one. The camera timing is shown in the picture below.

alternating camera trigger

The exposure time can be selected starting from 1 second to 8 hours. The camera can be used in bulb mode or manual mode (times >30 s bulb mode only). If used in manual exposure mode the exposure time in the camera must agree with the time set in the trigger, otherwise the timing will be incorrect.
To start the function the exposure time must be entered first by pressing the button multiple times (see presses/exposure table in interval section or trigger label). After the entered time is acoustically verified the triggering can be started by pressing the push-button again. This short movie is the best way to understand how this function works.

To connect two cameras to the SmaTrig you will need a cable which connects the focus wire in the trigger with the shutter of cam 1 and the shutter wire of the trigger with the shutter of cam 2. The wiring is shown below. The dashed wires are necessary for some cameras (Sony, Nikon, Canon EOS 40D...)

11. Inverted interval trigger

This mode is based on a slight but significant variation of the standard interval mode (mode 12.). It might be interesting for astro-photographers or (night-)time lapse fans. The only difference is that the trigger signal is inverted compared to the standard operation described below. Instead of short trigger pulses and long pauses, long trigger pulses and short pauses of 0.5 s are generated. If you set the camera to BULB now, it's possible to do very long exposures spread over different images. To merge these multiple images to one you can average them or better apply a "maximum of" operator (GIMP, Photoshop). This way you can prevent the final image from overexposure and reduce long exposure noise. Imagine a scene with a lit house and stars in the background. If you try to make the star trails visible using long exposure, you'll definitely "burn" the house. Exposing "by parts" and applying the max operation (or locally max or avg) to the image stack will give better results. This mode should also be useful for night traffic photography, airplane trails, ferris wheels, etc...
The usage is analog to the interval trigger described below.
The first example image shows different operators applied to a stack of 96 images with an exposure time of approx. one minute. Note the cool airplane trails. In the secod example four images with an exposure of 8 min. and two with shorter exposure are merged.

12. Interval trigger

As the name implies, the camera (or flash) is triggered periodically at different time intervals. This mode can be used to shoot time-lapse movies of growing flowers, moving clouds, traffic, construction and demolition of buildings, melting ice, parties, rotting food, crowds of people, sunrises, sunsets, etc. Capturing lightnings, surveillance, astronomy, time stamping, scientific experiments, stop-motion movies, averaging (noise reduction) or tourist removing are other possible applications. All this in Full HD or better!
The timer allows 16 different intervals listed in this table or the label of the SmaTrig. To activate the timer proceed as follows: Press the button N times to set the interval according to the table above. The trigger will verify the user entry by beeping N times (the beeps come in pairs to simplify counting). Now press the button again to start the timer. It can be stopped anytime by pushing the button again.

There is another "hidden" mode": If you push the button once as for the 1 s setting, but hold it down for more than 1 s (you will hear a beep), the variable interval trigger will be activated. The button hold time will be converted to the interval time. Example: If you press the button for 12.4 s you get an interval of 12.4 s. The duty cycle of this function is about 50%, meaning that if you set your camera to bulb it will expose for 50% of the interval time and wait for the remaining 50%. After setting the time by holding down the button, the button must be pressed again to activate the function. The timer can be stopped anytime by pushing the button again.

At very long interval times, the camera battery life becomes a problem. The camera should fall asleep between the shots to avoid exhausting the battery to early. To wake up the camera in a controlled manner, the trigger pulls down the focus wire 4 s before the shutter is released (only possible for intervals > 4 s). This feature can be also used to control lighting equipment as described here. The shutter wire is pulled down for 4 s. This is long enough to shoot multiple images as needed for HDR time lapse movies.

13. Long exposure

This mode can be used for taking very long exposures as needed for astro or infra-red photography. The exposure time can be chosen in discrete steps between 1 second and 8 hours. The times are listed on the SmaTrig label or in this table. Usage: Press the button multiple times to set the exposure time. The time setting is beeped back by the trigger for verification. Then, press the button once to activate the function. Holding the button for more than 1 s (beep) generates an additional trigger pulse for mirror lock-up.

14. IR remote release

configuration. Besides the normal usage for taking pictures remotely, many cameras allow to start and stop the bulb exposure with the IR remote control, so you don't have to keep the shutter-button pressed. It's also possible to shoot a bracketing sequence at once instead of pressing the shutter-button three times, very useful for HDRs.

15. Manual/Bulb trigger

This is the simplest mode of operation. The push-button works as an extension of the shutter button in the camera (only the fully pressed state is available: focus + shutter). If the button is pressed longer than 1 second, the trigger locks up allowing continuous (bulb) exposure without keeping the button pressed. The lock-up is signaled by a beep. The continuous exposure is terminated by pressing the button again.
The lock-up function in connection with the continuous shooting option of a camera can be also used to capture lightnings, etc...


This section describes how to use the SmaTrig for some typical photographic scenarios.

Shooting bracketed shots for HDRs

Set camera to MF • set camera to BULB exposure • connect SmaTrig • choose mode 1, 2, or 3) • push button according to desired bracketing width • push button again to stop function in case of overexposure • merge images (check out the free tool called "enfuse" and "enfuseGUI")

Shooting lightnings (all cameras)

Mount SmaTrig on the camera (hot shoe mount) • set camera to MF and RAW quality, manual or auto exposure • set SmaTrig to mode 9 • start function by pressing the button, the camera will be triggered at each lightning • terminate function by pressing the button again

Shooting lightnings (mirror lock-up support, Canon only)

Mount SmaTrig on the camera (hot shoe mount) • set camera to MF, RAW quality and manual exposure (or time priority) • enable mirror lock-up in camera • set SmaTrig to mode 6 • press button multiple times to tell SmaTrig how long it should wait after triggering. The time should be equal to or greater than the exposure time set in the camera. • press button again to start function • observe operation • terminate operation by pushing the button again

Taking high-speed shots (example: popping champagne bottle)

Prepare darkroom • position and fix champagne bottle • Set up and connect camera, flash unit, SmaTrig and microphone (sensor plug) • set SmaTrig to mode 8 • point the IR diode of the SmaTrig at the cameras IR sensor • set camera to MF, bulb exposure, RAW quality, and remote trigger mode • light off, torch on • wake up camera and flash • put finger on push-button of SmaTrig • torch off • press button (SmaTrig sends IR signal to camera, camera begins bulb exposure, do manually if no IR sensor in camera) • let the cork pop (most difficult point, try not to have your hands in the picture) • BENG! • SmaTrig terminates bulb exposure by sending IR signal to camera • check result, clean up, drink champagne...

Interruption-free capturing

Connect focus wire of SmaTrig with the focus and shutter wire of camera A • connect shutter wire of SmaTrig with the focus and shutter wire of camera A • connect all ground wires • set cameras to MF • set SmaTrig to mode 10 • choose bulb exposure or a fixed exposure time in camera • press the button multiple times to tell SmaTrig the exp. time • count the beeps to verify your entry • start function by pressing the button again • stop function by pressing the button again

Drop photography

Prepare drop setup, read tutorials on the net or here, use a burette • install SmaTrig and laser pointer on a rail, laser should point exactly on photo diode • set SmaTrig to light barrier function • focus camera, prepare flash • adjust delay by changing light barrier level or use a delay circuit • start function with delay if triggering the flash directly • triggering the camera will result in an additional delay of 50-120 ms

FAQ / Electrical data

Connecting a flash unit to the SmaTrig 2

The SmaTrig 2 can trigger cameras and flash units, as both rely on the same trigger principle. Connect the pin of the PC sync contact to either the ring or the tip of the camera jack connector (and the grounds of course). You can connect two flashes using ring and tip. The trigger voltage should not exceed 50 V (limit of BSS138 transistor).

Sensor connector

In contrast to the old SmaTrig version, the microphone is connected externally with a jack connector. Instead of the mic, other sensors can be used. The sensor signal has to be connected to the tip of the sensor jack plug. Refer to the schematics below for details. The microphone power supply on the ring of the jack plug can be used as power supply for external sensor circuitry if the current consumption is low enough. A voltage of about 2.4 V through a 2.7 kΩ resistor is available there. Keep in mind that the capacity of the coin cell is limited (approx 200 mAh). The mic supply is enabled only if one of the sensor modes is active. It can be disabled completely in the configuration. configuration

Light and sound trigger lag

The oscilloscope screenshot below shows the timing of the sound and light trigger. The upper trace shows the voltage at the photo-diode with a peak caused by a flash. The lower trace visualises the voltage at the trigger output, where 0 V is the triggered state. The trigger lag is about 0.2 ms. The article shutter lag measurements might be also interesting for you.

Switching heavy loads with SmaTrig 2

With some simple additional circuitry the SmaTrig 2 can switch heavy electrical loads such as lamps, solenoids or ventilators. This extension of the trigger is practical in connection with the interval function which activates the focus 4 s before the shutter is released. Connect the switch to the SmaTrigs focus wire to activate additional lighting equipment before each exposure. You don't have to keep your 8 kW lamp switched on for a week to record your plants growing;-).
The safest way to switch heavy loads is to use an opto-isolated device. The schematic below shows how to connect an opto-triac to the SmaTrig 2 to switch loads connected to the mains. There is a big variety of opto-triacs on the market. The circuit below was copied from a data sheet of the MOC3062. It is not tested!


Another option is to use a solid-state-relay with an optical input like the S202SE/S216SE series from Sharp. The connection of the low voltage side is analog to the opto-triac. The S216SE types can switch up to 16A. Remember that high voltage is nothing for beginners and it might stop you from photographing permanently!

Build your own SmaTrig 2.1

The circuit

The SmaTrig 2.1 is based on the ATmega88V microcontroller from Atmel (It is becoming obsolete and will be replaced by the ATmega88PA). This relatively small and versatile chip is a low power device which works down to 1.8 V. The ATmega88 is available in a TQFP32 package (used here) and the prototyping-friendly narrow DIP28 package. It is perfectly suited for battery operated equipment. It provides power-saving timer functions using a 32.768 kHz clock crystal. A lithium coin cell was chosen as power supply. The schematic of the trigger circuit is depicted here:



The most important sections of the circuit are explained below.
Triggering: T1 and T2 are responsible for triggering the connected device by pulling the focus and shutter wire to ground. The BSS138 transistor is rated with 50 V and 220 mA.
Rotary switch: The switch has two functions: it sets the operation mode of the trigger and connects the AVR to the battery. The switch provides a connection between the input pins and the power supply in all positions except the "0", where the circuit is disconnected completely from the battery. The AVR is supplied in a "parasitic" way through the protection diodes of the input pins.
Sensor input circuitry: C1 and R1 form a high-pass filter between the sensor input (tip of jack plug) and the built-in analog comparator of the ATmega88. Only transient (changing) signals can be detected by the SmaTrig. The positive comparator input is connected to the reference voltage at PD6 which sets the trigger threshold. The voltage is generated by the voltage divider consisting of R9 and R11.
Mic power: To allow the direct connection of a standard (sound card type) electret microphone to the trigger a power supply at the ring contact of the mic plug must be provided. This is accomplished via PD2 and R2. The supply can be also used to power some low-power input circuitry. The ring contact should _not_ be connected directly to ground (mono jack plug, etc.) to avoid high power consumption and shortening of the battery life. The power supply can be disabled in the configuration.
IR-LED: The IR-LED is controlled by T3 which is connected to PC0. The inner resistance of the battery and the on-resistance of the FET make a serial resistor for the LED unnecessary.


The one-sided board was designed with Eagle. The minimum path width and the clearance are 10 mils. This means advanced home-brew methods are necessary for reproduction. The PCB shown below was manufacture on one-sided FR4 1.5 mm material. The drills are exactly in the center of the pads.



All parts necessary to build the SmaTrig 2 are listed in the documentation available in the download section below. I tried to use standard parts only. All analog functions are based on the integrated comparator of the ATmega88, reducing the part count significantly. The most exotic part is the code switch. It is a hex-type with 16 positions manufactured by many companies. You can use any type compatible with the PT65 from Hartmann. There are types with a spindle and with an integrated (detachable) knob.

The BSS138 FET transistor can be replaced by a different n-type conducting at 2 V at the gate. The buzzer has no electronics inside. Any piezo-type can be used. It has a pin spacing of 7.5 mm. The photodiode can be replaced by any daylight type. A high sensitivity type is preferable.

The circuit is mounted in a small pocket enclosure (50x38x13mm). A hot shoe mount can be attached to it for better usability. It can be recycled from an old flash or made of two plastic plates glued together. It has no electrical connection to the camera. The light sensor must point in the direction of the lens if you plan to use the trigger for lightning capturing.

I designed a drill aid and a label for the rotary code switch. They can be found in the documentation in the download section of the page. The red symbols on the label correspond to modes which involve timer functions where the user has to push the button multiple times to set the time. The red numbers below the switch legend describe how many pushes are necessary for which time.

Assembly - tools and skills needed

Please refer to the DIY guide PDF for assembly plans and details.
We start with the circuit as it is more exciting than the enclosure preparation. You can find all detailed plans in the documentation in the download section. You should have some experience in soldering to avoid frustration. If you have never soldered fine pitch SMD devices before, read one of the countless tutorials on the net, an exhaustive one can be found here.
The most difficult part to solder is definitely the ATmega88 in its TQFP32 package. You will need thin solder (≤ 0.5 mm), a soldering iron with a pencil tip, and a loupe. Solder paste and a gas soldering iron are also a very good or even preferred options. Please, double-check the orientation of the chip before soldering! There is a small dot on the PCB where the mark on the AVR should be. Use the photos in the documentation for orientation. Be careful with the SMD caps (all 1206 types), as they usually have no marking. The resistors (all 1206 types) have a number printed on top where the last digit corresponds to the number of zeros that must be attached to the preceeding numbers to obtain the resistance in Ohm: 3304 and 335 mean 3.3 MΩ. The jack connectors can be mounted at an angle of 3-4 degree to fit the slope of the enclosure side wall they are mounted to. Do not mix up the IR and the photo-diode, watch the polarity. Some buzzers also have a polarity marking. If you use the integrated code-switch (left on picture above) solder it at about 1.7 mm above the PCB to align the knob nicely with the enclosure surface. Use a piece of PBC as spacer. The spindle type switch is mounted in the regular way without any extra spacing.
After all parts have been soldered, the circuit can be tested. The simplest indicator of "life" is the buzzer. Switch to position "F" (Manual/Bulb) and press the button down for more than one second. You should hear a "beep-beep". If you don't hear the beep, set the switch to "0" to disconnect the battery and search for the problem. Compare your PCB to the pictures in the documentation. Some solder bridges? Is the orientation of the IC and rotary switch ok? Battery?
If the Manual/Bulb function works fine, but some others don't, you probably forgot to program the EEPROM. Many functions look for settings in the EEPROM and find just a '255' if it was not programmed.
If the buzzer is ok, but you can't hear no clock "ticking" in the (active) interval modes, probably there is a problem with the crystal.
If everything is fine, the board can be mounted in the enclosure. Set the rotary switch to "0", or remember the setting to attach the knob at the right angle later (applies only to spindle version of code switch). For the integrated switch version the knob must be removed (see picture above) for mounting.
Now the enclosure has to be drilled. Print out the drill aid from the documentation ensuring the scaling is set to none (1:1). Cut out the aid and fix it on the bigger part of the enclosure with adhesive tape as shown below.


SmaTrig 2 drill aid 1 SmaTrig 2 drill aid 2

The dashed lines must align with the edges of the enclosure. Double check the symmetry and then copy the centers of the holes to the enclosure with a sharp device. Now drill the holes as precise as possible. Use a drill stand if possible. The bigger the holes, the higher the tolerance to misalignment. Too big holes look bad. The drill aid is a hit-and-miss thing, so be prepared to use a file to make everything fit. Now insert the PCB into the enclosure. The PCB fits very tightly. Use a screw driver to push the spindle of the rotary switch into the hole. Proceed as shown in the pictures below. Inserting the no-spindle version is easier. Now the label (and the knob) can be attached. You will find the label in the documentation ready for printing (1:1).

Software si Programare

The controller was programmed in C. The hex and the eep (EEPROM) file necessary for programming the AVR can be found in the download section. Use the programming pads on the edge of the PCB (reset has a special pad close to the chip) to transfer the code. I used an STK200 clone and Ponyprog. The fuse bit settin.g is shown below. If you program with avrdude the command is

avrdude -p m88 -F -c STK200 -i 1 -U flash:w:smatrig21.hex -U eeprom:w:smatrig21.eep -U lfuse:w:0x52:m

Option -F means 'ignore chip signature' and lets you program the new ATmega88PA chips with older versions of avrdude.


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