qbcan releaser

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Open Cosmos qbcan releaser.JPG

This document is the qbcan releaser user manual. It describes the qbcan CanSat releaser and its operation.

The qbcan CanSat releaser has been developed by Open Cosmos for the organisations that need a CanSat releaser to deploy CanSats from balloons, drones or other aerial vehicles.

Open Cosmos can supply a full deployment system consisting of a drone and a releaser. Please contact us for details.

Take a look at the releaser in action click [[1]]


In case you have any problems or questions during the operation or set up please post your questions into the Open Cosmos community so all the users can benefit from the content.

System description

The releaser is a time delay operated device designed to deploy CanSats by gravity from aerial vehicles such as balloons and drones.

The Open Cosmos qbcan releaser consists of two main parts:

  • Releaser body: Main body of the releaser holding the hinged door, the electronics box, volume for the CanSat and four attachment points.
  • Electronics box: Enclosure that contains the electronics that allow operation of the releaser: electronics, door's hook mechanism and battery.

The two parts of the releaser are 3d printed and assembled by Open Cosmos. The releaser is delivered with the software already in it with a default timer, see timer delay change section for more details.

Releaser body

The main releaser body contains the main volume to load the CanSat to be released.

The CanSat volume is a totally enclosed volume without any apertures in order to avoid entangling of any CanSat features with the releaser.

This volume is closed by a spring actuated door locked by the door mechanism. The latch mechanism and door have been designed to offer some level of protection for landings. The door hinge is spring actuated allowing a rapid removal of the door from the CanSat way when the releaser is actuated to drop the CanSat.

The four attachment points at the top of the main body are used to attach the releaser to the aerial vehicle. See attaching/detaching releaser to aerial vehicle section for more details.

Electronics box

Qbcan releaser electronics box compartment details.jpg

The electronics box is the compartment where the 9V battery, electronics and latch mechanism to unlock the door or lid reside.

The electronics consist on an Arduino Micro Pro that controls a battery powered servo motor that actuates the latch mechanism.

The door's hook in the latch mechanism retracts within a protected volume in the electronics box to avoid damage while landing.

The electronics box is mechanically connected to the main releaser body via 3x M3 rods with their respective nuts.

The box also contains two external switches that allow easy operation of the releaser:

  • ON/OFF: Switches ON or OFF the releaser
  • OPEN/CLOSE: OPENs or CLOSEs the door latch mechanism and activates/deactivates the timer.

The OPEN position is when the latch mechanism is retracted allowing the door to rotate. The CLOSE position is when the latch mechanism is rotated into the position to lock the door.

See operation of the releaser section for detailed instructions on how to operate the releaser.

CanSat specifications

The releaser has been designed following the official ESA CanSat guidelines that can be found in the following link: http://www.esa.int/Education/CanSat

  • CanSat max dimensions: 66 mm diameter x 115 mm height + 45 mm extra for external elements
  • CanSat max mass: 350 grams

Operation of the releaser


If you have any doubts with the operation, please post them in the community forum forum and we will get back to you. It is a good practise to read the all the points of the procedure first before performing the activity in question. This will give you a clear picture of which steps you will need to follow and understand the whole process better.


  • Always operate the mechanism via the switches. Never manually. Forcing it or blocking its movement could damage the servo motor or the mechanism itself. It is unlikely that injuries are caused though due to the low power of the servo.
  • Do not try to disassemble the mechanism or parts of the releaser apart from the electronics box from the releaser main body using the procedure detailed in the assembly/disassembly of the electronics box section. Some parts are glued and/or fastened in place in order to ensure the robustness of the assembly and their nominal condition could be compromised if tried to be disassembled.

A typical sequence to operate the releaser would be:

  • Attach the releaser into the aerial vehicle.
  • Switch ON the releaser.
  • Operate the OPEN/CLOSE switch to OPEN position, to reset the timer and/or unlock the door if its closed.
  • Place the CanSat inside.
  • Manually rotate the lid. Do not rotate manually the latch mechanism.
  • Activate the CLOSE switch to lock the door via the latch mechanism. At this point the timer is activated and starts counting.
  • Lift the releaser with the aerial drone.
  • Releaser is activated after the timer has timed out, dropping the CanSat by gravity.
  • Lower the releaser to ground.
  • Switch OFF the releaser.
  • Detach the releaser from the aerial vehicle and store safely.

Timer activation and releaser behaviour at time out

The timer is activated whenever the OPEN/CLOSE switch is toggled from OPEN position to CLOSE position.

Once the timer has timed out, the latch is automatically rotated by the releaser to the OPEN position to unlock the door.

To repeat a launch, move the OPEN/CLOSE switch to OPEN position. At this point, the latch won't rotate as it is already in the OPEN position.

Once the OPEN/CLOSE switch is returned to the CLOSE position, the latch will rotate again to the locking position (CLOSE) and the timer will start again.

Visual ON/OFF and timer activation aid

When the releaser is ON, a red LED is ON. It can be seen by looking from the direction where the CanSat is loaded.

If the timer is activated and counting, the LED will be blinking.

Attaching/detaching releaser to aerial vehicle

  • Switch OFF the releaser.

To attach the qbcan releaser to the aerial drone, ALL four anchoring points at the top of the releaser are to be used.

Each of the four points ideally would go to different place in the aerial vehicle providing spatial separation between the vehicle anchoring points to stabilise the releaser and avoid its rotation.

It is recommended to use then equally long ropes to tie each of the four anchoring points to the aerial vehicle. The length of the strings is recommended to be as small as possible to aid the stabilisation.

Carabiners or key rings at each extreme of the ropes can be used for easy assembly and disassembly.

Switch ON/OFF the releaser

To switch ON the releaser:

  • Move the ON/OFF switch to the ON position.

To switch OFF the releaser:

  • Move the ON/OFF switch to the OFF position.

Releaser behaviour when switched ON

The latch mechanism will be placed to the position indicated by the OPEN/CLOSE switch when the releaser is switched ON.

If the latch mechanism is in the OPEN position before switching ON the releaser but the OPEN/CLOSE switch is in the CLOSE position, when the releaser is switched ON, the latch mechanism will rotate to the CLOSE position and the timer will start counting. After the time out, the latch mechanism will automatically move to the OPEN position.

Analogously, if the latch mechanism is in the CLOSE position before switching ON the releaser but the OPEN/CLOSE switch is in the OPEN position, when the releaser is switched ON, the latch mechanism will rotate to the OPEN position. No timer is activated as the latch is in the OPEN position.

When the releaser is switched OFF, no action is taken by the releaser and the latch mechanism is left where it was before switching OFF.

  • Wait for the latch mechanism to be either in OPEN or CLOSE position before switching the releaser OFF.

Loading a CanSat inside the releaser

To load a CanSat inside the releaser:

  • Switch ON the releaser.
  • Move the OPEN/CLOSE switch to OPEN position.
  • Load the CanSat inside the releaser.
  • Manually rotate the lid. Do not rotate manually the latch mechanism.
  • Activate the CLOSE switch to lock the door via the latch mechanism while holding the door in place manually reacting the door hinge spring moment. At this point the timer is activated and starts counting.

Manual unloading of the CanSat

If for any reason, after the latch mechanism has been CLOSEd and timer activated the CanSat needs to be unloaded:

  • Move the OPEN/CLOSE switch to OPEN position.
  • The releaser door will be then free to open and the CanSat can be removed.

Electronics box disassembly and assembly from main releaser body

M3 nuts location
  • Switch OFF the releaser toggling the ON/OFF switch in to OFF position.

To disassemble:

  • Place the releaser on a flat surface and clear of objects.
  • Untighten one M3 nut from each M3 rod.
  • Slide out the M3 rods. At this point the electronics box is mechanically disconnected from the releaser.
  • Pull manually the electronics box from the releaser paying attention for the battery to not drop by gravity from its compartment. Never grab the electronics box from the latch mechanism or the switches.

To assemble:

  • Place manually the electronics box in the releaser location.
    • IMPORTANT: Pay special attention to cables from the electronics not getting caught or compressed when pusching the electronics' box into the releaser.
  • Slide each of the three M3 rods through the circular holes in the releaser.
  • Tighten one M3 nut in each M3 rod. A bit of play on the rods on their axial direction (1mm or so) is desired to avoid overcompression of the electronics box assembly.
    • IMPORTANT: Do not overtighten the nuts on the M3 rods compressing the walls that give support to the electronics box. The nuts are only there to avoid the rods sliding off but the electronics box is totally constrained with just the rods in place.
  • The releaser is ready to be operated.

Timer delay change

The releaser comes with software already programmed in it and is ready to be operated. The time delay can be changeb by changing 1 variable in the source code.

  • Default timer delay: 1 minute


  • Do not try to operate the OPEN/CLOSE switch if the releaser is OFF and USB is connected. Power from the USB is not enough to operate the latch mechanism.

If the default timer delay is desired to be changed:

  2. // Timer Variables
  3. //----------------------------------------------------------
  4. //*******************************
  5. //* Release time in miliseconds *
  6. //*******************************
  7. const unsigned long int release_time = 60000; // [ms]
  8. //----------------------------------------------------------
  • Upload the source code to the microcontroller
    • Disassemble the electronics box from the releaser following the procedure in the disassembly section.
    • Locate the square lateral hole that gives access to the electronics USB port.
    • Plug the USB cable to the USB port on the electronics holding the electronics board assembly to avoid disconnecting them from the electronics box.
    • Upload the software with the timer delay changed.
  • Test the newly uploaded code:
    • Switch ON the releaser.
    • CLOSE the latch mechanism via the OPEN/CLOSE switch.
    • Verify that the LED is blinking.
    • Count the time for the latch to OPEN automatically.
  • Switch OFF the releaser.
  • Unplug the USB cable.
  • Assemble the electronics box into the releaser following the procedure in the assembly section.
  • Releaser is ready to be operated.

Battery change

The releaser uses standard rectangular commercially available PP3 9V batteries.

  • Disassemble the electronics box from the main releaser body following the procedure in the electronics box disassembly section.
  • Locate the battery at the top compartment of the electronics box.
  • Place your hand covering the open section of the electronics box battery compartment and tilt the electronics box so the battery drops by gravity.
  • Disconnect the battery from the connector by grabbing the connector to avoid damaging the cable or the electronics assembly where it's connected.
  • Place new battery into the connector.
  • Place new battery into the electronics compartment.
  • Assemble the electronics box following procedure in electronics box assembly.
  • Releaser is ready to be operated!