We are announcing Version 2 of the EPM, Electro Permanent Magnet and the OpenGrab CAN daughterboard (OGCAN). A simple solution for cargo gripping for UAV’s and robots.


Introduction EPM V2

Operating principle explained in this video




Supported are RC PWM and CanBus with the CanAerospace daughter card. The EPM has an onboard PIC12F MCU with an in circuit programming header to allow easy reflashing.

Even lower power consumption; 400mA for 400ms at 5V per cycle or 800mJ.

On board tactile push button: Allows toggle testing the EPM on/off  having only the power connected

Cycle time: The Cycle time is 400ms or 2.5Htz. This solves the problem when the EPM is turned on and the target does not make perfect contact, the majority of the energy is used to move the target into  place rather than realign the magnetic domains, resulting in a much reduced holding force. With the fast cycle time one can turn the EPM on a few times in a row to make sure proper contact has been made.

Full bridge Thyrisotor drive circuit increases efficiency and reduces capacitor size .

Reduced magnetic interference allows mounting within 5cm of a magnetometer (please test it with your application)

Lighter- mass has been reduced to 47grams


Data sheet


Source Code / Parts Drawings

User Group / Help





Introduction of the CAN daughterboard 3689574886?profile=original

OGCAN is an open hardware CAN bus interface that allows to control OpenGrab EPM and monitor its state via CAN bus or serial CLI. Supported CAN protocols: CANaerospace, UAVCAN (full UAVCAN support comes April 2014).

OGCAN is built on STMicroelectronics STM32F103 MCU running RTOS ChibiOS, implements one CAN bus interface (ISO 11898-2, up to 1 Mbps), one TTL UART for CLI and optional CAN termination resistor (via jumper). OGCAN can be directly connected to EPM via two board-to-board connectors, as shown below.

Supported CAN protocols: CANaerospace, UAVCAN"




Source Code






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  • MR60

    And another one : is there a setup/installation/wiring manual/tutorial ?

  • Just use the base unit Hugues.

  • MR60

    To use PWM on/off command, do you need to buy the daughter board or is it standard with the base unit ?

  • Hello Gary,

    That would be awesome, I been trying to get to the wiki but there is never enough time

    I just added you to the chat with pavel on skype

    Euan, really nice job!!

  • My question - what's the advantage of the CAN daughterboard, from an Ardupilot perspective?

  • (Apologies for the sound in the video btw)

  • I have one. It works well. So I've ordered another!

    I'm building a payloader around it - here is my prototype in action - you can see how easy it is to operate:

    I do have some comments which you need to know:

    - For the PWM to work, you need a common ground with your rx, and a 3 way switch.

    - I powered it from a dedicated BEC...but apparently one is not needed. I was just being overcautious!

    - If you use the standard futuba PWM connector, you might need to replace the risers with 20mm versions, to allow some clearance. Your mileage may vary.

    - While it will hold 6kg, I think the most practical limit for a MR in flight is nearer 2kg, and you must pack carefully. This 2kg bottle was easy to pop off, due to the leverage. I plan to recommend a 1kg maximum load, to allow for normal flight.



    - You *must* use very low profile screws for the target plate, if you are securing it to the payload. The target plate needs to be in direct contact with the magnet for best effect. Alternatively, just use strong sellotape...:-)

  • Hi Hugues,

    See the purchase and other links above.

    And Ctech, would you like me to add this to the wiki or would you like to do so yourself?

    Like the CAN interface, would like to see that implemented for Pixhawk.

    Best Regards,


  • Hello Hugues,

    The price including shipping is 49.99$

    I would not recommend at all to go over 1.5kg per unit. Although the holding force is higher the slightest vibration or a not so perfect mate will cause your cargo to drop.

    And yes you can link as many as you want together, you can even wire them up parallel on the same RC PWM output. Just be careful with the power consumption if you going to run it of the RC rail.

    Also you might want to link them mechanically with a little flex between the EPM's



  • MR60

    what will be the price of this second version ?

    What is the maximum load I can grab ? If I need to grab more weight than one OPENGrab can carry, can I link them in parallel ?

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