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This 3S battery had a much lower internal resistance and there is a bit more ring as a result (And there was quite a bit of wire length between the battery and the board). Even so, the peak is about 17V, which is not a problem for the switching regulator (which has a 20V abs. max. input voltage rating). Though it is doubtful that the board will survive a 4S LiPo battery. Load Tests: Now, the cool part about a Magswitch ® is that you can turn it OFF. Here’s where the magic happens. It’s a great magnet-science demo, but you’re probably not going to save money with assemblies like this. It's easier and less expensive to just buy an MJ-95 or MJ-150 and get on with it. 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.
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. 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 But I could not reproduce the same problem as before by holding the hall-effect sensor near the current carrying wire as high currents flow. That was somewhat disconcerting, but par for the course. POOF! 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!
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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.
It is now tolerant of the input transient caused by plugging a 4S LiPo battery into the inputs -- there is no measurable ringing.Not much is different. The change is to the FETs and how they are driven. Previous magnetic switches were driven with 5V gate voltage. This circuit level shifts the gate voltage of the output switching FETs to 12V to extract every bit of RDSon that the FET is capable of providing.
When you rotate the knob, you’re rotating the top diametrically magnetized disc magnet by 180°. Now the magnetic field flows from one magnet, through the steel wall and into the other magnet. 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. across switch) EDIT 2018-03-29: The switch resistance measured above was taken from the two pads on the board. While testing the other 5 boards I noticed that the resistance was 25% lower when measured from the copper landing that I had placed near the sources of M1 and M2. That's significantly lower, which I did not expect. I connected up two more boards, using the landing pad for the B- lead. Here's what I measured with that configuration: 1.0mΩ @ 1A for the board using SS28 FETs. 1.2mΩ @ 1A for the board using IRLHM620 FETs. In the end, I did get a pretty good improvement in switch resistance from the SS28 devices. I assembled one of the second pass 30A prototypes using different FET switches than the first pass -- substituting a Vishay SiSS28DN for the IRLHM620. The Vishay part claimed slightly lower RDSon (1.6mΩ vs. 1.8mΩ @ VGS = 4.5V) and a higher max VDS of 25V instead of 20V. I thought, erroneously, that the higher voltage rating might improve the survivability of input transients when batteries are plugged into the input. The addition of R1 between the input and the LDO solves the problem by eliminating the capacitor (C2) that caused the ringing so a higher voltage rated FET is not required to support 2S-4S LiPo batteries.The Magswitch MagPress magnetic press has descended from one of the most disruptive tools, the MagPry. Designed to help welders to level sheets is the only way to level and align steel. Remove high/lows with ease by placing the magnet on low, prying on high and welding with the other hand. This method allows for an individual to align two sheets and weld the separate sheets 100 times faster than using dogs and wedges. The traditional method took app 20 minutes, Mag Pry, with a 1000Lb magnet, completed the process in 12 seconds. Magnetic Press Innovation The switch no longer is sensitive to disconnection by high currents. I ran more than 35A through it and it remained closed. This is what the input transient looks like without any circuit changes made for protection and R2 = 25mΩ for the battery resistance: 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? Load regulation is hard to measure without an electronic load, but seems to be better than the line regulation. Electromagnetic and vacuum lifting systems are costly in the long term regarding energy and maintenance costs. Magswitch ‘Greentech’ technology will offer you significant savings in energy and repairs while increasing productivity. Custom Solutions R10 needs to be a power resistor. When you insert 100mΩ of resistance into the input... Read more » I've been traveling a bit the last few weeks and came home to a bunch of PCBs and a few components that finally arrived from China. I had to prioritize. The BEC version was a first pass effort, so that got the highest priority. I knew that the BEC was going to need a second pass to fix the input transient problem so i only assembled a single unit. It was larger than I expected. I got accustomed to dealing with very small boards and this one is huge by comparison. Crappy Input Caps:NO 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? 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. 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.
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