The EPM Cargo gripper EPM-688-5 V1.21 from http://NicaDrone.com is now supported by APM:Copter master branch.
Master branch != widely tested! Wait for the 3.2 release if you´re not comfortable with that.
This setup has only been tested by the author.
All this is open source, check out the resource section at the bottom
What is an electro permanent magnet?
Check out this paper by Ara Nerses Knaian -: http://opengrab.googlecode.com/files/Electropermanent_Magnets_Knaian.pdf
Or watch the completed kickstarter project videos that go over the working principle
Very cool eh? I thought so...
How to setup:
Get the code: http://dev.ardupilot.com/wiki/where-to-get-the-code/
Open APM_Config.h and un comment line number 35 so your left with
#define EPM_ENABLED ENABLED // enable epm cargo gripper costs 500bytes of flash
Build the code: http://dev.ardupilot.com/wiki/building-the-code/
Upload the code: http://dev.ardupilot.com/wiki/load-the-code-ontoapm2x/
Complicated ehh?? If we can justify using an extra 500bytes of flash we could include the code in 3.2 RC1 which is due to come out in a couple of weeks
Connect with Mission Planner
Go to Config/Tuning->Full Parameter List->Find: EPM
Set either Channel 7 or 8 to '19' "EPM", This will allow you to control the EPM with that channel from your RC or Joystick
Set EPM_Enabled to '1', This will enable the EPM
Restart the APM Mission Planner: ->Actions->Preflight Reboot->Do Action
Mount the EPM with a minimum distance of 10cm from the magnetometer, make sure to check out the section "Magnetic Interference".
Prepare the cable assembly
Cable Color codes:
Yellow: Signal S_on/S_off
The Two Signal have to be connected to A7 And A8 on the APM2.X see APM2_analog_pinout as reference
The Analog output rail has power supply pins next to the signal pins but it is not recomended to use these pins because the current draw of the EPM during it's 3 second charge cycle exceeds the capacity of what the APM can supply on these pins. You are probably going to blow the onboard fuse or cause random brown outs, creating a flying Schrödinger's Cat.
Mount the EPM:
Connect the cables:
and we are ready to play- hahahaha
The EPM688-5 is designed to hold a cargo of 1kg securely and switch on and off effectively with low power consumption. 800mA at 5V for 3S or 3.4J per cycle.
Under the capacitor discharge condition pull either S_on or S_off high Via RC channel 7 or 8 for 3 seconds and then low. The capacitor is fully charged and the device is ready to cycle. Pulling either S_on or S_off high via Via RC channal 7 or 8, causes the magnetic field to move either in the on or off state.
WEIGHT AND CAPACITY
The complete device will have a mass of about 50 grams, and is capable of holding a mass of 7kg in optimal conditions, in practice it should securely hold 1kg of cargo on a quad.
So the APM uses a compass that is sensitive to the surounding magnetic field. The EPM can produce a sizable field that can interfere with the compass when it is in its on state, without a target metal attached ,if mounted closer then 10cm. Please be carefull since this has not been widely tested.
Order The EPM: http://Nicadrone.com
EPM Cargo Gripper Datasheet: http://code.google.com/p/opengrab/wiki/Datasheet
Drawings of parts and models V1.X and 2.X: https://github.com/ctech4285/EPM
Schematics and gerbers: https://upverter.com/eda/#tool=schematic,designId=aee8e8e33e656dad
Ara Nerses Knaian paper: http://opengrab.googlecode.com/files/Electropermanent_Magnets_Knaian.pdf
Original Kickstarter Project: http://www.kickstarter.com/projects/412473553/opengrab-open-hardware-electro-permanent-cargo-gri