Magswitch Technology MAGJIG95 On/Off Magnetic with 95 lb/43 kg of Vertical Holding Force Yellow

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Edit 2020-02-02: BHarbour pointed out my laziness in his comment. The following is a bit of extra work to solidify the design.] Reducing the standby current: My first thoughts were to add a snubber -- a series R and C across the inputs. This could be just a tantalum capacitor with an appropriate ESR value . The problem I found was that the capacitor had to be greater than 100µF and the series resistance (or ESR) around 100mΩ. I could not find a reasonable size ceramic 100µF capacitor with a 25-50V rating, or a tantalum with <500mΩ ESR. The solution for the snubber to work was to put 15x 10µF ceramic caps in parallel -- so I abandoned this idea in favor of adding resistance in series with the input. Every Magswitch product is proudly designed, developed, manufactured and tested by Magswitch to ISO 9001:2015 standards. Frequently Asked Questions What is Magswitch Shallow field?

With load current 35A, the voltage across the switch was 40mV (that's 1.1mΩ). Power dissipation is only 1.3W, which should not be a problem for a board even this small. I repeated the measurement with 20A load current and got 22mV across the switch, and the same switch resistance. No changes required. So here's the plan:

The Data:

The Magswitch magnetic square is the most versatile workholding and fixturing tool ever! Align and secure flat or round pieces of steel to fabricate angles. Pull corners, secure steel for cutting, use as a guide or make your own fixtures with our MagSquares. At this point I was pretty bummed out. It was obvious that the BEC was not capable of handling 5A as a continuous load. This result was not unexpected. I was boning up on thermal resistance and power dissipation of PCBs while traveling and had determined that a PCB this size could only handle about 0.5W of power dissipation to keep the junction temperature of the switcher IC less than 150°C. R10 needs to be a power resistor. When you insert 100mΩ of resistance into the input... Read more » It is now tolerant of the input transient caused by plugging a 4S LiPo battery into the inputs -- there is no measurable ringing. Power to the load can be switched on or off by momentarily placing a magnet near the circuit. This allows the circuit to be completely enclosed within the aircraft fuselage.The current drawn from the batteries while in the off-state mode should be as low as possible. It should take more than one year to discharge the battery.The voltage drop across the switches should be as low as possible to keep power dissipation, heat, and losses to a minimum.

This all looked pretty good. I decided to see what the input transient voltage waveform looked like for a couple of different battery types: Most of the extra area is for the larger area required by M1 and M2. I added space between U2, the Hall effect switch, and the high current ground trace -- hoping 3.5mm is adequate distance to prevent the switch from tripping off during high current events. If that doesn't work, then the Hall effect switch will have to be moved off the board. The landing pads for B+, B-, OUT+ and OUT- are not through hole -- I decided that the large 12-14 AWG stranded wire would undergo a severe 90° bend if forced into a hole, so now the wires are simply soldered to a landing pad. The landing pads will accommodate up to 120mil diameter wire (12 AWG). In addition, there are numerous vias to help spread the heat and conductance between the top and bottom layers. The board will use 2 oz. copper for improved heat dissipation.

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I had originally set the value of R2 = 10kΩ. I was sure it would work and did not really consider the impact on standby current. I don't usually leave the battery connected more than 3-4 hours; when the model is returned to its resting place the battery is removed. It would be better if the standby current was low enough that there was no need to disconnect the battery. This can be accomplished by raising the value of R2 to 1MegΩ. (A MegOhm is my personal limit -- enforced by a few years in the automotive industry. High values of resistance are subject to degradation over time by crap that collects on the PCB surface.) Replaceable pole shoes, cut maintenance cost and allow for Taylor made pole shoes to be fitted for repetitively lifted irregular shapes parts such as pipe.

The twist on this application is that it should remember the state of the switch if the input power is disrupted or disconnected for up to 10 seconds. It would be disastrous if the power glitched during a flight and the switch permanently disconnected all of the electronics controlling the operation of the aircraft. Those are 14AWG wires. I believe that 12AWG is the max size that the board will accommodate. 14AWG is rated at 34A for chassis wiring. If you think you will be averaging more than that, then the 12AWG is rated at 41A. It's all relative to power and heat -- use your discretion. Test Results: Is it physically possible to make something like this using a few neodymium magnets from K&J? Sure, it’s possible. In fact, when we started investigating how these things worked, we couldn’t resist building one ourselves! I decided to use a 4S battery and a 60A ESC to generate a current above 30A to test the circuit. When I connected a fully charged (16.8V) 4S LiPo to the input the circuit lets some of its magic smoke out. After all the cussing ended I was able to determine that the TPS70950 LDO had apparently latched up -- the current was enough to fuse the VIN lead open: Our dual roller guide has a dual set of roller bearings to firmly support the smooth gliding of wood through a blade. Requires our Woodworking Starter Kit and mounts to the Universal Mounting Base and MagJigs, sold separately. Resaw GuideNO drop zone risk. By using the MagReach 400 accessory the operator can control the load, under hook, from a safe distance, without entering the drop zone, increasing safety and reducing operator stress and the safety of those in the work environment. The Magswitch Magreach 400 allows the operator to stay clear of the fall and climb zones. What is the Pareto Factor, when using a Magswitch CE Lifter? Our Vertical Featherboard adds a dimension of dual plane workholding. For use with the Woodworking Starter Kit and the Pro Table Featherboard. In the Magswitch Workholding System, it mounts to the Reversible Featherboard Attachment, Universal Mounting Base and MagJigs, each sold separately. Pro Table Featherboard Voltage drop across FETs during 40A load: 13.5mV. That's 0.34mΩ switch resistance. With a 40A load the switch will only dissipate about 0.54W. It should be able to handle this load continuously without overheating. I used to care about how the symbols looked, but I'm using Diptrace for schematic capture and it is not possible (at least I don't know of a way) to get the pins on top or bottom to have the proper pin name rotation (i.e. horizontal). I took your suggestion to heart though and made a new symbol. But I left the CLRB pin at the lower right side because it made more sense to keep the RC components on the output side. Magswitch is a breakthrough in control and strength of permanent magnets, making the shipbuilding process faster, safer and delivered at a lower cost,” said David Morton, Chief Executive Officer. “Magswitch is being used in over 100 major shipyards around the world.

This is what the input transient looks like without any circuit changes made for protection and R2 = 25mΩ for the battery resistance: Now, the cool part about a Magswitch ® is that you can turn it OFF. Here’s where the magic happens. I've decided to pursue four types of switches. One for low current/low voltage applications such as RC gliders without motors. Two with higher current and voltage for motorized RC aircraft. A fourth with an integrated battery eliminator circuit (BEC). Low Current Switch Specs: I used a 22Ω 1W resistor for an easy load test. The BEC did not have a problem with this load and the output decreased only about 20mV over the entire input voltage range.The final result was a lifting frame that utilized Magswitch’s shallow field patented technology to load and unload the snow plows safely and effectively into the press brake. The Magswitch Advantage Safety I soldered two 30AWG Kelvin leads to the PCB pads near where the wires were connected. The location of the Kelvin leads makes a big difference in the measured voltage drop across the FETs. Since I don't have any precision/programmable load that can generate 40A I used my Tundra airplane's motor and ESC to provide the load. The Tundra draws very close to 40A during full throttle from a near fully charged hefty (5Ah) 3S LiPo battery. There may be some users that want to locate the hall-effect sensor away from the main circuit board. I added pads to allow leads to be soldered instead of mounting the sensor on the board.