[HN Gopher] A Battery Spot Welder Made from an Old Microwave and...
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A Battery Spot Welder Made from an Old Microwave and Excessive
Mahogany [video]
Author : CaliforniaKarl
Score : 44 points
Date : 2021-09-09 23:23 UTC (23 hours ago)
(HTM) web link (www.youtube.com)
(TXT) w3m dump (www.youtube.com)
| nimbius wrote:
| nitpicking but as someone with a scientific mind, i found the
| whole 'i dont know how a transformer works but lets screw with it
| anyway' mentality to be infuriating.
|
| Electroboom would too.
| [deleted]
| blahblah23 wrote:
| Isn't it incredibly dangerous to disassemble microwaves?
| cronix wrote:
| Absolutely, for people who do not know what they are doing.
| Anything with high voltage capacitors is dangerous unless you
| know how to safely discharge them, and the magnetron in
| microwaves specifically.
| rcoumet wrote:
| This is borderline FUD, just like people arguing that kernel
| programming is dangerous, when it's just another programming
| environment.
| CamperBob2 wrote:
| Nah. You'll live.
| CapstanRoller wrote:
| It's less dangerous than servicing CRT televisions/monitors. If
| you know how to safely discharge the big capacitor and never
| try to energize (or dismantle) the magnetron, it's pretty
| benign.
| rcoumet wrote:
| No, it's not.
|
| Just basic safety around capacitor, don't take a deep breath
| around the magnetron or shatter it / grind it into fine dust,
| and you'll be fine.
| taylorportman wrote:
| The magnetron can have insulators made of a toxic substance
| that can be dangerous as a dust. This guy is just using the
| transformer for it's convenient laminates and primary winding -
| probably could have used a similar transformer with suitable
| current handling capacity but dead microwave ovens are fairly
| common. I have 3
| summm wrote:
| Some beryllium ceramics I heard...
| rruark wrote:
| These MOT based spot welders transfer far more heat to cells than
| capacitive discharge welders. This can result in the damage to
| heat sensitive components inside the cells which is the same
| reason that soldering isn't recommended for lithium cells.
|
| To get around those issues, I built a capacitive discharge spot
| welder for tabbing lithium ion cells a couple years ago:
| http://robruark.com/projects/welder/welder.html
| korethr wrote:
| What is the cause of the excess heat transfer? Is it mainly an
| excess pulse duration? I notice that the project in the OP was
| being pulsed on the order of 100s of ms, long enough to get a
| visible glow. Or is the excess heat caused by the fact that the
| OP runs at constant current for the entire duration of the
| pulse, where a capacitive discharge design is going to have the
| current falling off during the pulse? Or is it a blend of both?
| anfractuosity wrote:
| I quite fancy getting a microwave oven transformer to make a
| pretty powerful electromagnet.
| swayvil wrote:
| Another source for a big stepdown transformer : an old arc
| welder
| korethr wrote:
| In the end of the video he lists off the number of things he did
| that were fancier than necessary. One of them was the use of an
| Arduino for the pulse duration and switching. I found myself
| reflexively commenting, "It's called a 555 timer." I'm confident
| that the same function could be more minimally implemented with a
| 555 timer and maybe a couple other supporting chips. But he's
| probably getting more consistent control of pulse duration and it
| was probably easier for him to implement as well.
| geon wrote:
| Having digital timer settings would be tricky without a
| processor, I imagine.
| sokoloff wrote:
| It's also likely faster to implement as a one-off for a
| hobbyist and, using a low-cost MCU, cheaper than building it
| around a $0.10 555 if you want to make a product.
|
| https://cpldcpu.wordpress.com/2019/08/12/the-
| terrible-3-cent...
| redis_mlc wrote:
| Fun fact: the cavity magnetron found in micraowaves was one of
| the most secret inventions of WW2, and guaranteed victory for the
| Allies.
|
| It was invented to generate 10 cm waves in a compact package,
| which are ideal for radar. Although Germans and Japanese did
| early research on the magnetron, the Allies leap-frogged them.
|
| The Americans had a university campus (around 4,000 staff) design
| production units for literally everything larger than a jeep that
| moved .
|
| A Brit hand-delivered their prototype to the US, and the US
| solved some issues and productionized it.
|
| Because the magnetron is made out of a block of metal, there was
| no way to destroy it after an airplane accident. But the Germans
| weren't able to adapt it, and admitted it was beyond their
| understanding at the time.
|
| Ironically one of Germany's most advanced signals airplanes was
| captured just off a beach in England, but politicking between the
| navy and army meant it was left in seawater until it completely
| corroded. (You can identify these special signals planes by
| numerous antennae mounted on the nose.)
| ziml77 wrote:
| LTT has a video on a very simple battery powered battery spot
| welder https://www.youtube.com/watch?v=aHNmVV7THBs
| flipflipper wrote:
| Timing is inconsistent and the contacts will stick and weld
| together after a bit of regular use. Solid state is better if
| its designed well. Checkout the kWeld.
| https://www.keenlab.de/index.php/product/kweld-complete-kit/
| hughrr wrote:
| I think I'd have just hit aliexpress and bought a battery welder
| for $30 shipped.
| lstepnio wrote:
| I ordered one of these and applied all of the recommended
| "fixes. The unit failed after two spot welds. I would not
| recommend and my experience seems to be mirrored across the
| internet.
|
| The Malectrics kit is drasticly superior with reasonable price
| and resale value tends to be high if you're worried about
| limited use against cost to aquire.
| jandrese wrote:
| This homemade one bodged out of a broken microwave is probably
| safer.
| progre wrote:
| What's the fun in that?
| ricardobeat wrote:
| What are the dangers here? What happens if that thin insulation
| between the copper bars breaks? Can the current jump to you if
| you use this bare handed?
| swayvil wrote:
| Well it's only 2 volts. So nothing will happen. Unless your
| hand is all sweaty maybe. Then maybe you'll feel it. I wouldn't
| worry.
| sokoloff wrote:
| Agree. You can feel a 9V battery on your tongue, but not on
| the sweatiest of hands IME. (I still quick-check 9V batteries
| on my tongue.)
| tres wrote:
| uh... wut
|
| I believe it's the amps you need to worry about; "amps kill."
|
| I believe it takes about 1 amp to kill a person.
|
| This thing is outputting somewhere around 55 amps (if I
| remember right).
| Robotbeat wrote:
| But for a given resistance, you don't get the amps if you
| don't have enough voltage. V=I*R. Don't they teach that
| equation any more?
| bufbupa wrote:
| If the the insulation breaks the tool short circuits and the
| welding tips don't work. Electricity follows the path of least
| resistance, so given how close the welding tips are together I
| doubt it would ever choose to go through you; especially any of
| the sensitive parts of you. You'd have to be bizarrely well
| grounded for it to discharge current through your body.
| CapstanRoller wrote:
| The most dangerous thing here is energizing a MOT with its
| stock deadly high-voltage secondary coil. If you re-wind the
| secondary to be low voltage as described in the video, it's no
| more dangerous than any other project requiring a mains power
| supply.
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(page generated 2021-09-10 23:01 UTC)