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LazyH

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  • LazyH commented on dan's instructable High Power LED Driver Circuits
    High Power LED Driver Circuits

    Good instructable but you seem to have the wrong impression of why LEDs need to be constant current. when you turn on an LED, regardless of how little power you use or how much heat sinking you have it WILL heat up, the more an LED heats up the more it conducts power, the more power it conducts the hotter it gets, the hotter it gets the more power it conducts the more power it conducts the hotter it gets... This continues with the LED getting hotter and hotter and conducting more and more power that even without "moving to a new environment" your LED will eventually fail and burn out regardless of how precisely you've set the voltage. LEDs can never be driven by constant voltage unless you want them to die an early death.

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  • Making a Fridge Compressor Into a Vacuum Pump

    The main limit to the level of vacuum one can achieve is actually the force required to overcome the Reed valves. This is why roughing pumps made specifically for vacuum work use sliding elements to create the seal rather than passive valving. When you get down to a certain level you can't pull enough vacuum with ANY rpm or displacement to overcome the force of the Reed valves.

    Use your compressor as it came from the appliance, most require an external capacitor but if you don't need to add one then don't, no reason to make things more complicated when you don't know what effect it might have on the system.

    "There is no such thing when you are dealing with vacuum."Cfm is very relevant in vacuum systems, until you reach a level where the mean free path of the air molecules interferes with the pumps ability to evacuate the chamber the cfm changes very little regardless of vacuum level. The effect that this has is that the overall mass of air is reduced because a given cfm has lower amounts of air molecules in it at lower pressures. Even high vacuum pumps such as diffusion pumps and turbomolecular have a cfm rating that we've used with a bit of math to create a controlled environment for high voltage plasma based on input flowrate and a targeted vacuum level. It's pretty common to use this cfm rating in high vacuum industrial systems.

    "Putting 2 in series would theoretically result in a vacuum of ca. 1/900"This is actually false. The reason for the lower limits on these fridge compressors is that the Reed valves (one way valves) require a certain amount of pressure to open up. As long as the Piston can pull enough of a vacuum to create that pressure difference then the Reed valves will open. If the vacuum gets low enough then there won't be enough pressure to overcome the Reed valve, the absolute vacuum will never drop below the pressure required to open these valves no matter how many pumps you have afterwards. This is why purpose built vacuum pumps often use sliding sealing elements to control valving like in a rotary Piston pump, because then there is no pressure to overcome like in a system that uses Re...

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    "Putting 2 in series would theoretically result in a vacuum of ca. 1/900"This is actually false. The reason for the lower limits on these fridge compressors is that the Reed valves (one way valves) require a certain amount of pressure to open up. As long as the Piston can pull enough of a vacuum to create that pressure difference then the Reed valves will open. If the vacuum gets low enough then there won't be enough pressure to overcome the Reed valve, the absolute vacuum will never drop below the pressure required to open these valves no matter how many pumps you have afterwards. This is why purpose built vacuum pumps often use sliding sealing elements to control valving like in a rotary Piston pump, because then there is no pressure to overcome like in a system that uses Reed valves.The instructable mentioned a rotary pump, but the pump pictured wasn't actually a rotary Piston pump which is likely why the author didn't experience better vacuum levels with that compressor. A rotary Piston ac pump is the taller cylindrical pump, they don't quite last as long due to the sliding blade seal between the Piston and chamber wall, but they should hypothetically work better for creating greater levels of vacuum.

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  • LazyH commented on Machine Right's instructable $20 CNC Machine
    $20 CNC Machine

    I was wondering the same thing, especially since it's so easy and cheap to buy stepper drivers specifically for bipolar stepper motors rather than trying to mess around with a unipolar setup and building your own drivers.

    Personally I'm using something like this:https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F382986266190This is because that way I can use it to build a 3d printer, and if I want more functionality in terms of laser engraving or millin it's easy to take the output of d9 (typically used as a fan output) and routing that to either my Dremel input (if it's a voltage matched DC motor Dremel) or voltage divide to the input of my laser controller to make a laser engraver work which I got here:https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F332810623708Still assembling so we'll see how it goes.

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  • LazyH commented on Josehf Murchison's instructable Magnetic Wire
    Magnetic Wire

    that's the problem, they might not get the point. I found this article because a friend of mine asked if he is getting the right copper for a transformer because none of the wore in the tv he found would attract a magnet, and he thought magnetic wire would be magnetic, he was almost ready to use bare steel wire in a transformer because he misunderstood your answers. similarly some people might think it's ok to break open a tv picture tube outside to vent the supposed Mercury vapor you talked about, but not only is there no Mercury (it would ruin the path the electrons have to take to the screen and serve no purpose whatsoever) but they would also be very likely to injure themselves from the imploding screen if they did try it. when instructing people you need to make sure they understan...

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    that's the problem, they might not get the point. I found this article because a friend of mine asked if he is getting the right copper for a transformer because none of the wore in the tv he found would attract a magnet, and he thought magnetic wire would be magnetic, he was almost ready to use bare steel wire in a transformer because he misunderstood your answers. similarly some people might think it's ok to break open a tv picture tube outside to vent the supposed Mercury vapor you talked about, but not only is there no Mercury (it would ruin the path the electrons have to take to the screen and serve no purpose whatsoever) but they would also be very likely to injure themselves from the imploding screen if they did try it. when instructing people you need to make sure they understand what you're telling them so they don't hurt themselves, otherwise I may not have a friend anymore if he listened to you because you assume everyone will just understand even if you tell them the wrong thing.

    there is no Mercury because there is no gas, it's a complete vacuum. the main concern with the picture tube is that the tube can implode quite violently if cracked and the phosphor coating can be toxic if I remember right.

    wire, not wore. time to eat my own words.

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  • LazyH commented on LazyH's instructable Dash Cam Mic Upgrade
    Dash Cam Mic Upgrade

    That does sound like a great idea. I'm currently getting my electronics "lab" set up in my new house. The wife and I are finally homeowners so I can set up my lab in the basement and my shop in the garage however I want to, which means I'm going to have a lot more time to work on projects like this one. I would like to get a couple more of these dash cams because I would like to do some videos while driving. I talk to myself driving all the time on the 40 minute commute to and from work through the countryside so it's the perfect time to just get some ideas on camera, and if I can get a good microphone and use them to cancel out noise between them I may be able to get some pretty good videos too. That'll probably be the next project after fixing my car.

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  • Fireproof Carbon Foam from Pyrolysed Bread

    I may be wrong about this so anyone else correct me if I am, but the carbon foam will eventually burn away, it is simply and effect of the insulating properties that only allow the tiniest portion of the surface of the material to get hot enough to actually combine with oxygen. From what I understand this is like aerogel, being made of glass foam you'd think it would melt instantly under heat from a torch but there are several demos of aerogel insulating things like crayons and flowers from a direct blast from a torch without any visible affect on the aerogel, simply because such a small part of the surface was affected by the torch. Heat it long enough and the bread will burn and the glass will melt, it's just really slow.

    from what I understand both can have an equally clean burn, but because hydrocarbons are typically fluid in nature (gas like propane or liquid like octane) they will be able to burn more efficiently (more completely) due to better mixing with the oxygen in the air and reducing the chances of co and soot/ash. Of course there is almost never any PURE hydrocarbons or carbon to burn, hence why you have ash left after a charcoal burn, and it also depends on the environment of the burn too (insulating container, oxygen rich or lean atmosphere, high air currents, etc.). I've never had any residue of any kind left after a propane burn for my forge or metal casting, but charcoal will always leave some kind of ash or residue, especially if its not homemade like ours is.

    You don't even need to purge the oxygen, it will usually burn away before it starts affecting the carbon, but that's if you have a mostly sealed container with a small vent for gasses to escape. I used to make small chunks of charcoal and charwool from fabric and branches just wrapped in aluminum foil and tossed in a campfire. It's impossible for the foil to completely seal what's inside and what little oxygen there is will get either pushed out with the browns gasses or will burn with the browns gas and become inert to the carbon that remains. I use to take a 20 gallon steel drum and will it with wood from out at the farm and do the same thing, the lid wouldn't completely seal it so I had a working vent, but it kept the oxygen out long enough to completely pyrolize the whole thing, add...

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    You don't even need to purge the oxygen, it will usually burn away before it starts affecting the carbon, but that's if you have a mostly sealed container with a small vent for gasses to escape. I used to make small chunks of charcoal and charwool from fabric and branches just wrapped in aluminum foil and tossed in a campfire. It's impossible for the foil to completely seal what's inside and what little oxygen there is will get either pushed out with the browns gasses or will burn with the browns gas and become inert to the carbon that remains. I use to take a 20 gallon steel drum and will it with wood from out at the farm and do the same thing, the lid wouldn't completely seal it so I had a working vent, but it kept the oxygen out long enough to completely pyrolize the whole thing, adding argon just adds a bit extra insurance to make sure it all goes right.

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  • Desktop Michelson-Morely Interferometer

    Where do you get single surface mirrors, an ebay search didn't return any results at all?

    Where do you get single surface mirrors, an ebay search didn't return any results at all?

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  • LazyH commented on jds1969's instructable Homemade Spot Welder
    Homemade Spot Welder

    Sorry, I know it's a late reply, but there might be someone else interested in this as well so here goes, anyone feel free to correct me if I get it a little wrong.The workpiece acts as a resistor, it's not a very strong resistor (low ohms in other words) which is good because that allows more amperage to flow through and melt the metal more effectively. In addition, your primary has a different impedance to dc and ac, and with ac it has a different impedance if the secondary is open vs the secondary in contact with metal to be welded. Your multimeter measures resistance by putting an electrical current through the coil.Electrical energy is only generated in a conductor when a magnetic field changes within close proximity to said conductor. Since the primary windings act as an electroma...

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    Sorry, I know it's a late reply, but there might be someone else interested in this as well so here goes, anyone feel free to correct me if I get it a little wrong.The workpiece acts as a resistor, it's not a very strong resistor (low ohms in other words) which is good because that allows more amperage to flow through and melt the metal more effectively. In addition, your primary has a different impedance to dc and ac, and with ac it has a different impedance if the secondary is open vs the secondary in contact with metal to be welded. Your multimeter measures resistance by putting an electrical current through the coil.Electrical energy is only generated in a conductor when a magnetic field changes within close proximity to said conductor. Since the primary windings act as an electromagnet, that means energy is only transmitted through a transformer when the magnetic field is generated or collapses, this doesn't happen with direct current like in your multimeter, so your multimeter only reads the short circuit resistance or dc resistance of the coil, whereas if you measured the resistance to alternating current, you'd notice that the impedance would change depending upon the resistance and winding of the secondary coil.

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