Inside an NVR (No Volt Relay)
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- Опубліковано 5 кві 2023
- An NVR (No Volt Relay or No Volt Release) is a safety device commonly found on most workshop equipment, that acts as an on-off switch, but will default to off if the power fails.
I thought it would be interesting to take one apart, and it was interesting to find that the off button also applies force to the contacts to make sure they part reliably even if they have welded together slightly due to the switching current.
The shading ring on the magnet core is used to cause a phase shift so the AC powered magnet doesn't lose force as the sinewave passes through the zero crossing point. That also reduces the risk of buzzing from the coil. It's similar to the approach used in shaded pole motors to provide rotational direction. Here's the Wikipedia page for the shading ring:-
en.wikipedia.org/wiki/Shading...
This unit came from a UK seller. www.ebay.co.uk/itm/115501562742
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:- www.bigclive.com/coffee.htm
This also keeps the channel independent of UA-cam's algorithm quirks, allowing it to be a bit more dangerous and naughty.
#ElectronicsCreators - Наука та технологія
At first I thought "no-volt relay" was going to be a euphemism for something that had a bad time. Like "light-emitting resistor"...
Thank you for that phrase!. That is how I shall refer to incandescent lamps in future.
Nonsense, an incandescent bulb is a perfectly correctly functioning light-emitting resistor (LER)!
Or just a silly name for a mechanical switch.
@@lightcycler4806I’m stealing this!
@@asteroidrules actually a silly name for a latched relay
I remember reading about motor starting controls in a 1910 electrical applications book. They used a lever to cut out resistances as a lever is moved from contact to contact. At the full on position, a holding magnet keeps the lever in that position. If the power fails, a rather strong spring pulls the lever to the off position. So yes, this type of no-volt control has been around for a very long time. Thanks for the video Clive.
The magnetic holding of the rheostat style system was also so the motor didn't get started on full current.
Fascinating, never actually knew these existed. I've seen machines with them before, but didn't give them a second thought as anything more than just a switch.
toaster
Usually you don’t notice the feature unless the device is disconnected from power
The shading ring doesn’t just eliminate buzzing, it creates enough of a shifted magnetic field so that the coil doesn’t release on the zero crossing.
In the US, toasters work similar with the lever pressing down contacts which power the electromagnet to hold the lever down until the timer or manual release. Only there they tap off about 30vax on the neutral side of the heating element and then create 25 vdc for the coil and 5vdc for the electronics.
That's actually a really clever cost cutting measure to use the heating element as a resistive divider for powering the electronics.
@@TheRailroad99 Thats usually how they drive the motor in a hairdryer, with one diode to create pulsed DC for a brushed motor.
Its also the reason why most hairdryers can't blow completely cold air.
Unfortunately that phase shift does not come for free, the copper ring does have eddy currents induced in it creating heat losses, not just inductive load.
I have just replaced my kettle, the plastic on the old one was disintegrating (glass kettle).
If it was removed from the base it would switch of in a similar manner to the item here.
The new one is the same and I suspect a similar magnetic 'hold on' device.
Will dismantle the old one, Clive-fashion, and confirm.
@@blg53 but a toaster is used for heating anyway
Very interesting. I remember as a boy studying the diagram of an electric bell in my Science Encyclopaedia: a coil attracts a metal part, but when the metal part has moved enough it breaks the contact and turns the coil off, so it springs back to make the contact again, and so on. Attach a clapper and put the bell next to it, and you get noise. This is the same principle, except that it only "strikes" once: when contact has been made, it stays made until broken by outside influence.
Electro magnets can be used for all kind of neat things. That ringer is one of the basic things. This NVR, I had actually never heard the term before, is a quite ingenious use of the electromagnet.
A few toasters I have use the same type of mechanics. When the tray is pressed down it closes two switches for both live and neutral and powers an electromagnet holding the tray down against the power of the springs. When the thermostat reaches temperature it break the circuit to the electromagnet which releases the tray to spring back up and breaks the connection to the heating coils.
One of the toasters was extremely cheap and clearly built to a budget. In this one side of the switches are left bare to the inside of the toaster. A single breadcrumb got in between the contact surfaces and the toaster was out of commission until I got it out.
It's a very simple design but when the tray isn't pressed down the inside of the toaster is completely safe as both live and neutral is open. Poke around with a fork if you like as there's no power no matter if the plug was wired correctly or not. And if the power goes out it pops out the bread so no risk it starts a fire when the power comes back on.
This switch just has positive feedback, while the bell also had negative feedback. The combination of both positive and negative feedback and some sort of phase shift is what makes an oscillator.
See also: electromechanical rectifiers.
@@Scrogan ummm...no.
The condition required for oscillation is positive feedback only.
@@blahorgaslisk7763 it's basically the same as a power tool switch that uses a separate contactor. The only difference is it's all self contained.
@@blahorgaslisk7763 NVR is also a term used on network video cameras. It means "network video recorder".
Back in the 1990s I worked on a boxmaking machine _that made the box around the product_ from a roll of stock, basically the product was the form (six one gallon boxes packed snug kinda like how butter is). It had several switches like this around it and not only did they feed the coil but the coil held a second sensor contact in on the backside for each button station that then went to the neatest thing I'd ever seen.
A master stop button that would not only stop all the equipment when pressed but NOT stop each individual station on the machine, but when the power dropped to the entire machine it would yank that button in _and turn it past the key interlock while spitting out the key if one was still inserted_
Test at start of shift when you take over the machine.
Rolling die with cammed cut bumpers on a sliding platform, scarifier to rough up the plastic coating on the glue-shut surfaces, initial tab and crease that twirled the box around to slide onto the product held in place by spatulate blades that swung/slid, bottom and top closer slides with a fast little slap-around on the end that made it all happen. The product would leave the end of the machine with the 6 gallon boxes packed hard-snug inside another sealed carton. The individual motions could be operated from each sub-control with a jogging button. About 22 feet long. Two cables along the top sides all the way along it like bus stop-pulls going back to that master stop with bump bars here and there. Was completely in-house built too! Had a dream years later that I'd been operating a giant strange bassoon.
Neat. I love it when things are designed simply yet perform their function perfectly.
Could be handy for use with a small generator, so that when the generator is stopped, the electrical load is disconnected. That way, when the generator is next started up, it will be in a known off-line state.
I have a similar arrangement with a 100A contactor to isolate the 20kVA generator when it's off-line. It requires that not only does the changeover switch need throwing over, but it also requires a deliberate action on the part of the user to put the generator on-line.
I've seen this done with a N.O. pushbutton, a N.C. pushbutton, and a relay. It's probably been done that way for a century. But, this is the first I've seen where the buttons and the relay are integrated like that.
I was taught to wire it this way in DT class many years ago.
I use to make my own using a relay and 2 switchs to switch a car headlight off when I switch the engine off, thats back in the days of triumph dolomites
Machine safety laws demand the NVR functionality, and an integrated device like this is the cheapest/easiest way to be compliant, so you'll find them on basically every stationary tool/machine made in the past however many years.
Often combined with the big red e-stop button on a lot of the cheaper machines, they just put the e-stop button on a hinged cap over this on-off switch. (I'm personally not a huge fan of that one, but it does the job)
Shaded pole relays are also referred to as "slugged" relays the telephone industry used these to prevent the line from dropping during rotary dialing and certain switching functions.
I built a home made exchange from old strowger parts as a child. I couldn't get slugged relays but I "slugged" ordinary relays with an electrolytic capacitor so that they stayed in during dial pulsing
This takes me back to one of my first circuits built around an electronics education kit. It was an alarm circuit using a momentary switch and a relay that latches. I felt completely empowered that I had made a bedroom security system at age 10 or so. I still remember when the latching circuit made sense for the first time to me.
Nice! I changed the switch on a lathe a couple of years ago and fitted one of these (looked like the same as the one you have). Practically every modern tool such as pillar drill, table saw and angle grinder has these as it's not just the power cut scenario that these are great for but the unplug at the main then when pluggd back in the tool doesn't start up. The NVR is not a lot more expensive than a simple switch but they are a lot safer and only a little more effort. Thanks for making the video!!
Thank you, that brought back memories of repairing all sorts of MEM contactors when I was an apprentice. This device is so much more simple and lower on component count though.
Looks like how modern toasters work! Unplug the cord when it’s on, and boom! Handle pops up!
Very similar mechanism, just an additional variable timer switch that ejects the bread when its done
Really liked this. When the example use for this type of relay was explained, suddenly the whole design made sense.
Just subscribed and it took me 2 and a half months to watch all your videos that are still up
Yeah, I've seen these once in a while and had learned the principle many years ago, but it was still interesting to see what you had to say about them. Thanks!
I have retrofitted similar switches to several of my stationary power tools. The tablesaw, shaper table (upside-down router for moving the work against the spinning-bit of death), and drill press all are now set up with this kind, and I've been of half a mind to set up the bench grinder with something like this as well. I've never needed to use them for-cause on the tablesaw or shaper, but I've had plenty of times where the drill press bound-up when drilling something and I needed to stop it quickly and easily.
Back in vocational we built a similarly functioning circuit for a 3 phase motor with a contactor and push-buttons, and for some of my classmates it was already a difficult concept to grasp... I must admit that when a wye/delta start function and DC brake was added, I also had to mull it over a wee bit.
The DC brake operated by opening the delta at one corner and feeding DC into the windings in series from a diode bridge and capacitor.
That is actually a well designed manual control relay. Saves the electrician the extra step of having to hardwire a holding contact and electrically defaults to off position if power is lost. A clever hybrid. Contacts look beefy as well. What's not to like.
The cheap plastic used for the lower case. I have a tabletop drill that has a simple on off switch that has the exact same black plastic back. I went to remove the "yellow safety key" for storage and when I went back it would not insert into the handle. On disassembly and further examination the plastic had shattered into multiple pieces. Took a while but with epoxy and tape I was able to reassemble it and was working again.
always educational !! i enjoy the diversity of items that get pulled apart and reverse engineered!
Thanks for explaining the 'shading ring' on the coil! I found one of those on a solenoid many years ago and always wondered what it was - unfortunately there was no such thing as the 'internet', let alone UA-cam, in those days so I just passed it by!
I have learned so much from you these few years. Really appreciate you sharing your experience here. Cheers ❤
On one hand, I love how Big Clive educates on the wide range of components available. On the other hand, he gives me quite the shopping list...
I just love the engineering that goes into switches. There's something so positively satisfying about a good click and a solid connection. I also have a thing for the tactile aspect of buttons that puts me maybe slightly off center on the bell curve of people who care about buttons...
One of the first circuits we learned as electrical fitting apprentices was the 3 phase d.o.L (direct on line) starter. Like you said basically the same thing using one of the contactor auxiliaries energising the ‘hold on’ circuit, usually 110v.
Cool! What a handy device. Love things with such simple design that do their job really well. The name's confusing, though. No volts allowed! Current only! In this switch, we divide the power factor by zero!
The no volt bit is to indicate the automatic reverting to the off position if power fails.
Thanks for another great video Clive 👍
Been a subscriber for years. Your videos are amazing some I am on the edge of my seat and then you have ones like this one that I can follow at a leisurely pace. Sometimes they are just plain soothing. Must be your voice. It’s always calm and peaceful you are a great narrator and video creator. Never had a chance to let you know. Just thought I would share how your videos effect me. It’s always positive. Keep it up Clive, you are truly one of UA-cam’s best content creators on here. I always look forward to your videos even though I know electronics well but not as much as you. Hey who said old dogs can’t learn new tricks. I have picked up a ton from you. Like all my LED screw in lights have been modified like you showed and have yet to have a failure. I am under driving them. The the first one I did, I forget exactly when but it was right after your first video on that and I thought why not try it. I have 4 drawers with bags and every component and whatever value you want. I do quite a bit of custom work for people. I often build light controllers for lighting someone added that’s not factor on their car.
I have had many people lately asking why I don’t use an Arduino. My answer is simple. Arduino still requires relays, circuitry, and programming. If something breaks it can be a crap shoot. So I am able to build a circuit that fits their needs and build from components on a prototype board and waterproof it with a weatherproof box. In the 30 years I have been building these different modules I haven’t had any failures of my customers cars. But I have no idea how it healed out in the long run. I have a customer that has a 1990. I did a light conversion in 1994 and everything is still working. The car is kept in a garage and not driven in the rain. I think that’s pretty good especially for someone who has does electronics for a hobby. Been at my whole life. No school for electronics. But at age 5 in the in 1981, I was in the newspaper and the associated press picked up the story and it was all over the country. Someone sent me 3 brand new Edison bulbs which all 3 are in a good and glass and wood case. Also got a letter from the president of Sylvania and he sent me a placemat with all the light bulbs they made. Also got a tie with light bulbs embroidered on it from him also a job offer that when I graduated college I had a job waiting for me there. I got into mechanical stuff around age 8 and really enjoyed it. Fixing watches with my grandfather and fixing and modifying bicycles. I am a mechanic or probably more like a technician because I find the problem and why it occurred. I will break out the schematics for the car and figure it out. I do have one expense Snap-On tool. It’s called the Vantage and does everything a meter can also has a scope and you can check ignition with it. But the main reason I got it is because of the database. Pick out any year, make, and model and find the component you need to check. It gives the plug shape, pin out and color code. Also it gives you 3 different teas to check it to verify it is bad or good. Much better than just guessing and throwing a several hundred dollars part at the problem and if didn’t fix it because there was a short in the wiring.
I do enjoy you vids. Always something new and interesting and often something I have never seen. 🙂
Simple and interesting. Nice teardown.
I always thought these were switches. Learnt something new today.
Never knew that! Thanks Clive I have learnt something today, an easy but brilliant design 😊
Another good one, Clive. Now I want to take apart my table saw switch!
What a lovely little unit
What a simple design. I don't think I've ever seen this type of design used on any commercial/industrial product though! Always a separate button contact and relay/contactor.
You're going to see them everywhere now.
@@bigclivedotcom Why ?
Is there a shortage of proper contactors or something ?
@@psirvent8 $$$$$$$
@@psirvent8 If China, Inc. has its say, we may see a lot of dodgy NVR switches. 😊
The new, exciting, shag-0-tron (wait for it) 3000 and 1 😆
Looks to be ideal for single phase.
Nice find there Clive.
;)
I was interested to see how they work, because the old epb (electric pneumatic brake) units i drove for BRITISH RAIL, network southeast, were fitted with a No Volts Relay and helped to perform various actions on those all electric passenger trains (slam door stock, now defunct). Class 415 and 416, known as 51s, 57s and 63s, the years of manufacture.
Ok, that was cool. Cheers for making the video.
Wishing you a very Happy Easter Clive.
Woah, I'm surprised I've never heard of a mechanism like that before. That's super cool!
Thats a very smart thing, clever use of selenoid to make things safer. i'm impressed
A simple and straightforward safety device, but it’s amazing how many people think the controls are just simple on off
It was very interesting seeing the inside of that. Having installed many of those, I've always wondered what it looked like inside.
KIS Keep it simple, perfect explanation
Hi BC, thanks for the view inside. I've used these for a good few years in my workshop and know first hand what they do - but not how they do it. I've always known them as an NVR - a "No Volt Release" switch.
I have one of these hooked up to two sockets on my workbench.
So every appliance I plug in automatically gets an emergency stop with it.
I also hook up my vacuum to one of the two sockets, certainly when I'm working with a saw. So after sawing something, the first thing I do is shut down the vac with the stop button, and the saw is immediately disabled too and safe to set up for a new cut.
The shop vac is loud enough to never forget to turn off the power.
Interesting construction. Much of the equipment in our workshop has one of these. I always assumed there were more switches inside, rather than the buttons actuating the relay contacts directly, but I guess it makes sense that as a mass-produced item it'd be more cost-optimized than that.
I wonder what else you could use these for. I reckon you could actuate it electrically using a pair of additional relays: one to interrupt the power supply for a short time to switch it off and another one that turns it on again by bypassing it temporarily.
Interesting. Such a simple and old technology is finding new use. I enjoy things like this, it's very similar to the mechanism used in toasters that Alec from Technology Connections explored a few years ago.
Thanks for measuring and mentioning the coil power consumption! 3VA (probably 1.5-2w) seems reasonable enough for a 16A relay
I've used that 4 pole off-on latching contactor trick on single phase loads. All you need is a normally open and normally closed switch and off you go!
Hi Clive , you always make such interesting tear-down videos. I wish you would've been able to show how the emergency stop button works but that part you didn't get a replacement for so I understand
I did a full teardown on an emergency stop button. It had a huge number of parts.
@@bigclivedotcom Really? Goodness, that seems that strange to me. When it comes to most things, simplicity is better, and especially when it comes to an emergency stop. I would've thought the emergency-stop would like... Forcefully sever the electrical circuit. In a "have to get this button serviced before it _can_ operate again" manner.
I think it's this video: ua-cam.com/video/6qYsNtrscPs/v-deo.html
@@ShadowDragon8685 You _want_ people to be quick to hit the E-stop if they think something might be wrong. So making them a problem to reset would be bad, because people would be more hesitant to use them for fear they'd waste a bunch of time if nothing turned out to be wrong.
Woodworking hobbyists like to add these to their power tools and they're a great safety feature. But one thing to watch out for is that the cheap chinese ones are usually rated for far lower loads than bigger tools like table saws will draw. Either you'll blow the switch right away with the inrush current, or the switch will fail soon after. A cheap fix for this is to have them control a contactor that does the switching instead, this is what I did on my table saw and it works great. At the cost of some extra space and wiring, of course.
I've heard of two other terms for these types of switches, No Volt Return and No Volt Release, same acronym I guess. No voltage no persistence of connectivity (so long as all is well). Anyway they are cool :) There's slightly more complicated version of this style of arrangement, often used in telecoms back in the day, pretty much used as mechanical transistors, relay logic circuits, if you like.
Thanks.
I have worked on shop equipment, and freight lifts with switches of that sort. Never really thought how they functioned.
Quite interesting indeed. It makes total sense.
I have had to replace three of NVR switches on various machines. A pillar drill many years ago, a small milling machine and my garden shredder. In every case the problem was knackered contact's. They can be cleaned to extend their life but it is only a temporary fix. They are only worth fixing if a new one is not to hand, better to replace them as they are fiddly and time consuming to fix but only take a few minutes to swap over if youvhavecthe correct form factor.
The one on my lathe is still the original fitting, for about 20 odd years, so wear seems variable.
I worked on a piece of equipment that had a relay that would pop open when a low voltage signal was sent to it. This was used as a safety shut off when of any number of situations occurred such as over temp or over current.
Awesome Video big clive
Positively guided safety relays keep my machinery safe. Expensive but reassuring.
Quite interesting! Think I may add this to my list of future upgrades to my drill press and other potentially spicy power equipment; including a standing grinder [w/ no guards whatsoever] that's in dire need of one of AvE's "Predates safety" stickers - as it most certainly does. Thanks!
a new hoppi type device with a fun button nice
Wow super video 👌
Would love to see the 3 phase version if you happen to come across one 😉
Thanks again Clive! Blessings mate
I had to figure these things out when I bought a cheap Chinesium belt grinder, that was mysteriously on sale for even cheaper than normal and was being discontinued.
It turned out to be wired wrong from the factory, I forget exactly how but they had somehow mixed up input and output so the relay kept buzzing and arcing madly as it tried to turn itself on and immediately off again all the time. Rewired it by just pulling off the spade connectors and plugging them in the right way around, it's worked fine ever since.
It is a nice safety feature, in that a machine cannot suddenly turn itself on when plugged in or after a power outage.
really cool thingy
Very nice buttons :)
Also available in industrial applications are manually operated circuit breakers with options for either ("under voltage" or "over current") trip relays fitted internally as per order / specifications .
Clive, I picked up an emergency shutoff switch for petrol. I don't plan to use it as intended, but plan to add it to my sign and plaque wall from various businesses such as a bank sign prohibiting rollerblading on the property. This I got from a contractor that was to raze a bank property. Another one is a cattle crossing sign.
Oooh goody, there's loads of these on workshop machines where I work 🙂🙂 time for a coffee & a study
That's actually very clever.
Very common in safety applications, and usually have multiple contacts all switching together. The idea being that you have a safe state - if supply fails, it switches off and isn't on when the power comes back. There are others which use a large contactor plate that is held on by the solenoid when powered, but gravity on the plate holds it off once the solenoid power cuts off - the reasoning is that gravity never switches off and always goes in the same direction, so you can count on it.
This reminds me I really need to make one of those emergency stop buttons for my 3d printer,
should be useful for when it fails into rats nest mode and prints into thin air
Yeah, emergency stop buttons are quite valuable for 3D printers, despite their relative innocuousness compared to huge machines and/or those with limb-amputating blades! So I have a toggle button on my 3D printer's enclosure that disables _just the stepper motors_ - because I've had too many cases of nozzles being driven into the print bed, scarring the print surface and even permanently deforming the bed or the frame it's mounted to.
So this button instantly halts all movement, but without killing heaters, requiring a mainboard reset, reconnecting OctoPrint, or even re-homing any axes _that the mainboard didn't try to move while the drivers were disabled_ :) (of course, the expected and actual positions will differ if any movement is attempted while drivers are off!)
It's also _safer_ than pulling the power out from under the drivers' feet while motors are moving. I recall reading in some docs for Trinamic motor driver modules (TMC2100/2130/2208/2209/…) that motors should be stationary when the driver loses power and that the drivers' !EN/enable pin should be used to turn them off instead - which is what my button does. Obviously the drivers won't be fried if that's ignored a few times (or a simple power outage would kill drivers every time), but I figure they mentioned it for a reason!
[See Watterott's SilentStepStick "Pinout + Powering" page]
However, my 3D printer is heavily customised, so I doubt this will be practical to replicate with most machines :(
Those customisations include a PCB I designed to hold 5 "Pololu-style" stepper motor driver plug-in modules, connect back to the mainboard's !EN, STEP, DIR, GND pins for each motor channel, and to the motors themselves. (There's also some other functionality.)
The button works like this:
• The !EN pins are active-low (0V=enabled; 3~5V=disabled) and all have 10k pull-downs on my PCB to keep them enabled by default.
• The !EN pins are still connected to the mainboard (a Smoothieboard v1.1), so the G-code "disable motors" command still works (mainboard pulls !EN up to 3.3V).
• The !EN pins are also connected to 5 separate "C"/Common terminals across two 4-pole relays with 24V coils (the printer's supply voltage and, more importantly, _the motor drivers'_ supply voltage).
• The corresponding "NC"/Normally Closed relay terminals are connected to 5V, forcefully disabling !EN when the switch is off or when there's no 24V supply. (It's all 5V-tolerant :))
• The toggle button simply engages the relay coil by connecting 24V direct from the power supply. (There's also a back-EMF diode across the coil.)
• This also ensures the motors are disabled if the 24V supply is switched off but 5V is still available from USB. Without this, and depending on the components and configuration used, _the drivers can try powering the motors from 5V USB!_ That just results in unpleasant noise from the motors (and can damage the drivers, apparently). I used to have that issue but some later changes stopped that happening even without this button.
There's no real need to use a relay; this is just what I had available and was convenient to wire up. I'll eventually replace the relays with some optoisolators or even just some transistors. I want to keep each driver's !EN pin separate from the others so they can be enabled/disabled individually if desired, but I can't immediately think of a justification for using optos.
That said, these semi-chunky relays emit a more satisfying PING noise than a solid-state component ever would! 💜
Thanks for the interesting disassembly, Clive. A shame about the cheap plastics used, that stuff looks like the easily shattering type of cheap stuff. It ultimately makes you wonder about the safety of the switch.
It's quite chewy plastic, so I wonder if the damage occurred at the factory while it was being inserted.
Always a delight to watch your vids. I’ve used a fair number of NVR switches. Where I’ve included an emergency shut-off mushroom or, particularly when using several around the machine, I’ve used 5 terminal NVRs to avoid running the motor current around the machine. A tear-down of a 5 terminal NVR would provide an interesting comparison.
Quite a timely video to coincide with the recent release of Tim Hunkin's solenoid and relay video
Very interesting. I have a central heating 'thermostat' that is battery powered but has an internal relay. Clearly the relay is designed so that it doesn't take current in either on or off state or the battery would not last very long. I would pull it apart to examine it, but the missus would have a blue fit... I imagine it has a rocker with springs to keep in either state and a couple of coils to change state. Great video by the way, I hadn't given these switches much thought until today.
It sounds like a remnance relay. Often with a latch and release coil.
I should take mine apart. Technically one can pull a little current in the idle state without the furnace/AC noticing and drop a little voltage in the on state without it shutting off, which could explain those AA cells lasting for years.
Never seen one built down to a price like that.
I used to repair machines that had relays and solenoids, the solenoids had copper across the core to stop residual magnetism building up in the actuator, holding on the actuator longer than it should. You have to hand to the manufacturers, they have it down to a fine art where to us friction contacts against wires to shorten assembly time.
I had one of this but slightly different. On part was same. You press plate to electromagnet but off was only opening coil supply connection without pushing on plate
Good show. I could not rap my around how a shaded pole electromagnet, transformer, coil, relay, contactor worked because I had only ever saw melted burnt up ones.
That as an intereting teardown. A simple cevice but cleaver.
Very interesting i have not seen them before. It looks like a mechanical version of a latching relay setup.
The silica gel probably came from your snack drawer. That's where I naturally keep mine. I wish those switches came in 12oV version. I'd buy some .. now back to my wine and blue cheese ..
Clever!
More of a latching relay🤔 I like the psychical mechanical contact separation , very good 👍👍
If I had designed it, the OFF switch would be a normally-ON switch that breaks relay current when pressed - letting the relay spring back to its unpowered state. It would be just as reliable (I think) as counting on a power interruption letting things reset.
"Green eye for 'good', Red eye for 'bad', and punch'em inna nose for 'sure, whatever.'"
Ribbed contact for extra comfort, nice. Interesting thing, I wouldn't use it when it was someone else's life on the line but for home use it might be OK for the price. 2x👍
this reminds me when i built a three button with a three wire controller that used two double pole relays that did reverse and off for a simple DC low voltage motor
such a nice construction.. no screws or glue inside. now if the case was openable without breaking, but i guess heating up might help.
'Shaded Pole' is my new band's name. If I had a band.
a simple stop start circuit used in contactors for industrial equipment for many, many years
I had this exact one on a huge industrial fan, and one day I went to push it and it exploded! The casing flew apart and it was one of the biggest electrical bangs I ever heard. 😅
Interesting.
Makes sense but I’ve never encountered one that I was aware of.
What a cool safety switch! I bet it has saved many people from accidents!
And the contacts are ribbed for your pleasure! But I bet they don't last as long as solid contacts would?
OoOoOoOooo Shag-a-tron, love it 👍
I wish more appliances had that I once used a Grinder and forgot it on luckily no one was near when the power came back on
The concept of operation reminds me of the mechanism in a toaster, quite similar.
Thanks
algorithm manipulation
The Shag-A-Tron Sex Machine comes with an emergency safety switch Im Impressed!
I've one for 400V 3-phase motors, it's wider and has three sets of contacts, the only drawback is that it only monitors the two phases that power the coil.