Fact: Upverter’s open source users are the greatest. And they build amazing designs! This week we have picked Andreas Jochum, (a.k.a ctech4285) “OpenGrab” Kickstarter project design with Jeffrey Bishop and Luis Montoya. A few words from the designers below:
“The concept was to build an electro permanent magnet – a magnet you can turn on and off and which does not consume energy for static operations. The idea came from a paper by Ara Nerses Knaian.
It’s a nice solution for cargo lifting for a UAV such as the quadrocopter and there are lots of other nice things you can do with it. Check out the Kickstarter video above for an simple explanation of what the EPM is and how it works.
In order to realign alnico magnets one needs about a 40kAm field for 100uS and in this design that turns into 5kA turns- that’s pretty hefty and requires lots of power ~30kW including ohmic loses….
The circuit : A logic high on Sig 1 causes the connected OR gate to produce the trigger for the thyristor. The 100nF series gate capacitor on the thyristor with the pull down resistor causes a short trigger signal, about 5us – this discharges the 60uF, 330V main capacitor through the winding.
When the capacitor is discharged the current will stop flowing and the thyristor goes into its off state.
Holding the pin Sig 1 high causes a delay circuit made of capacitor and resistor to switch the LT3585 into power delivery mode, charging the capacitor to 330V in about 3s.
The delay is necessary because the charge current is above the holding current for the thyristor and would cause it never to turn off. Sig 2 has the same function except it turns the second thyristor on and discharges the capacitor in an opposite winding.
The LT3585 photo flash capacitor charger working on the flyback principle charges the capacitor in a few seconds. This part is pretty much a straight copy from LT’s reference.”