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Messages - badpeter

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1
Electronic circuits / Re: CRT hacking ideas....
« on: June 20, 2019, 07:28:00 PM »
^Potentially... If i remember correctly horizontal is 15 khz and vertical is 60 hz (mains frequency).

For now I will just use it for "oscilloscope music". Check out Jerobeam Fenderson on Youtube. He does phenomenal stuff vectorially drawing graphics with sound. I hooked it up to the sound system yesterday. Coils are 2 and 14 ohm each. Speakers are 6 ohm each. It kind of works but needs some tweaks to display things correctly.
Will post a vid as always, when it is done=)
Also I found RGB bias knobs at the back to make the screen any color. Turned it sweet scope-green for now.

2
Electronic circuits / Re: CRT hacking ideas....
« on: June 18, 2019, 11:35:16 PM »
I think I am going to use it for "scope music" by connecting a small bluetooth amp to the coils. They say 15 w is enough.
I wonder, is there a realistic way to control each of the 3 electron beams to change color? It is feeding static which becomes a white dot, but what if I hang a large variable resistor on each of the connectors (granted I can find which one s which), maybe I can turn individual beams off...

3
Electronic circuits / CRT hacking ideas....
« on: June 18, 2019, 07:20:16 PM »
After a recent and rather successful trip to the recycling area, I found and old GE CRT TV (tiny one) with a vcr and a blockbuster batman tape stuck in it ;D. I cannot imagine who would keep something like this until friggin 2019 but thats besides the point...

I was always a big fan of CRTs, and I was wondering how can I hack it into something cool. And by "cool" I mean being able to control the video signal in some manual and interesting way.

Decades ago back in school I have done the classic hookup of sound output to deflector coils to draw Lissajous figures and I tried building a crude scope as well... I want to take this in some sort of NEW direction, maybe somehow control the color?

The other thing I have is an Arduino and I have several programs with TVOut library (I wrote code for pong for example), which works via composite input. It is BW only, but maybe something can be done about it.
Wondering if anyone has any unusual ideas!

4
^^^Yesterday I found a steel valve cap just the right size, that probably can be used as a crucible. Can't wait to test it out! needs a bit of cutting which ill have to go around somehow. I wonder whats the draw is going to be. Due to its shape it cannot be taken out of the coil though.
Wish I had any welding tools or such, maybe Ill find someone who has that.
Dagger hopefully on Friday=) New patented "sunken" mould style will prevent metal from escaping on the sides. 8)

I wonder if it is a good idea to find optimal power consumption by shorting turns of the coil to quickly change its characterictics (easier than fiddling with caps) and watch how output changes.

peterspaco - satisfying to watch the molten surface! I may try something like this, my dslr has some manual settings for video, maybe I can get away without filters even. or use an old floppy to cover the lens!

5
Capacitor banks / Re: Bought huge capacitors
« on: June 13, 2019, 06:14:58 PM »
This immediately reminds me of youtuber "PhotonicInduction" who does all kinds of very odd things with crazy parts like that!

6
Alright people, here it is...
Thank you for the valuable suggestions - I did not think of oxygen issue at all. I wonder how less the deterioration will be if I add either a ceramic shield or somehow make the whole thing happen in CO2 atmosphere (yes, for my kind of "lab" that be a bit of an overkill!)
I will probably entertain the idea of getting a drilled out STEEL crucible somewhere. Will need to be very creative with that. (Curie point a possible issue?).
Will do maybe one more melt/vid with graphite crucible, not to get too repetitive.
Anyways, the current vid is self-explanatory. lots of commentary and measurements given.
If I cleared PLA, it would have worked wonderfully.
Wonder if i should melt the sphinx (since its not great) or leave it as souvenier and recast my dagger with new material (i found a small source of copper recently!)


7
Alrighty... while the next video is being cut I'll share these, hopefully new insights.

I received my new 2 kg crucible. I chaged the coil to a 5 turn coil. This time, I WEIGHTED the crucible before use so I can see how much graphite is lost. And, it seems, a lot! After an hour runtime a 234 g crucible lost 25 grams of graphite. And I can confirm with absolute certainty that power draw depends on amount of graphite - it was at a healthy 1083 W with newly inserted crucible, and by the end was about 970 w as graphite was lost. I will not be surprized if for my next melt I will start with those 970w. The amount of material in the crucible seems to have insignificant (although measurable) effect on power draw.
So this creates a practical problem. I do not want to pay 15-20$ for a new crucible every ten melts. Also, even bigger problem is that with a tiny crucible it is very inconvenient to remelt things you have casted - you d have to laboriously cut it up in small pieces.
A truly useful crucible should be at least the size of cookie tray ingots, and good for many melts.

So, my next R and D will be devoted to being able to manufacture crucibles with clay/plaster/sand/whatever mixed with graphite. There got to be a recipe somewhere. Or switch to steel container, but I have no idea where to get something with thick walls.
Another idea is two concentric pieces of pipe acting as a heat jacket. Loose graphite can be put between the cylinders and replenished as it burns out - to keep power output consistenly high.
But at that point, I might as well design a regular electric kiln that will not have those ridiculous problems with small impractical crucibles, constant power draw issues due to burning graphite and all other sorts of maintenance that come with the iduction setup.

Anyhoo, the new vid is coming!

8
Hopefully I will be able to contribute with some new insights once new crucibles and other stuff arrives!
I feel left out =)
Maybe I'll try something different meanwhile

9
Molds: I use 50/50 plaster / sand mix, also 2 plasters for 1 water. Found information suggests that pure plaster cannot stand heat shock very well so sand makes it softer (although weaker) so it doesnt crack. Oven treatment is super neccessary so the mould doesn't explode on contact with hot metal from steam forming throughout. (it dries for couple days too before that but it is not enough)
Pure sand casting doesnt have this issue, but it is a chore to work with. I ve used it in the past for my other propane vids.
Transformer would hum only slighlty louder on overload. The massive fan under it drowns any possible sounds. It is not a part of the system in any way and connects separately to mains power.
The shunt does nothing at the moment. Crappy ebay meter burnt out and i left the shunt until I get a new one. As I explained in the description, to measure DC current just divide power (blue meter) by DC voltage (orange multimeter) (aka 700w/46v=15a dc.) So I have about 15 amps dc going in the induction unit. It can also be calculated the long way by utilizing turn ratios on transformer and ac current on mains, but thats the long way.
The hot metal is yellow to white, and is quite bright. It even shine through thick insulation. It loses brighness quickly when crucible is extracted.

So basically now I am going to wait until i get another different crucible from ebay (also ammeter). If i see increased power with new crucible, it will be conclusive that graphite is responsible for the most power draw. 
Meanwhile I may cut the existing crucible in half and plug a small coil, see how that goes. 
 

10
So...
Casting: there were 3 problems with moulds: lack of air holes, difficulty aligning two sides, significant crack between two sides. I will redesign the way the mould is, hopefully 3d print something for the mould to address those issues. Also I hope it can be reusable. Riser can be increased too.
I still have one more test to run with lost PLA method, will see how that turns out.

Metal: It melted completely, but I didn't stir it enough and didn't skim. I think convection doesnt do much.  Will try borax as a lot of people seem to use it. It is weird that if you have 7% Al you get that golden shiny color. Try 15%... and it starts looking like it is all Al, althought most of it is copper! In other words, I have put too much Al in this alloy. resulting alloy is still quite strong though.

Power: something is going on with this! With the same setup, every run has less and less output. I tried a quick melt yesterday, max power decreased by another 100 w. I dont know whats going on except my theory with crucible getting thinner and thinner. Imagine if I could get all 1800 w out of this! I'd be able to melt iron (and add it to my alloy). Will have to wait until new crucible from ebay, if power goes high again, I d say that be the proof. Rather inconvenient that crucibles have such a limited life. I wonder if there are any other options beside graphite... 

11
Finally! :)
The dagger didn't turn out pretty but the rest works okay. Hope it answers some questions!


12
I finally got to do the casting yesterday... ;D ;D ;D
So I can confirm that aluminium melts in about 15 minutes and copper indeed takes just an hour (my setup is unchanged from the specs that i mentioned).

Also I found out that 50/50 plaster/sand mold, pre treated in an oven DOES withstand thermal shock and doesn't explode like I worried. Great for ingots and other things. The dagger turned out crappy due to air bubbles - i forgot to make the air holes. I think I can use this mould one more time, although I kind of ruined it getting the piece out.

Now my power got even lower to a ridiculous 570 W (wtf!) I thought hard about it and realized something... crucible is withering away. It is much thinner now. Dont know where all that graphite is going but every firing i get slightly less and less power. This got to be the explanation.
The amount of metal inside seems to not affect power drawn. Looks like the amount of graphite is determining factor.

Now I am hearing people add borax to purify the alloy. Will have to do that for cleaner result.
I recorded my experiments, just got to cut the vid!= )

13
There wasnt much dross, copper was clean, mostly from av cables. Coil has a diam of 12 cm and something like 16 turns.
Here is my youtube channel where I melt some aluminium with my other diy propane kiln (sword and ingots in another one). When I finally get to make an induction video will post that on there too.
/>Also, on unrelated note, the epic power plant tour vid may be of interest to high voltage enthusiasts... but thats a different story...

14
Hightemp: I think the only way to get more power is lesser-diameter coil and more material/graphite in that diameter. I don't think I can alter my current setup much anymore.
My donut is using two secondaries in paralel to help with distributing high current over twice the wire as well as for cooling reasons (more turns take up more area of the donut). Adding things in paralel will do nothing. To draw more power - something has to consume it (aka work piece). It cannot be forced.
I have made some ingot molds outta plaster+sand (50/50) as well as a mold for a british ww2 thin dagger off a 3D printed piece from Thingiverse. I also printed a sphinx figurine to test out lost PLA method. When i did that, someone suggested purchasing a roll of water soluble PVA filament and just use that to print with! that be so much simpler.
Re power supply, I see that ebay has so much more to offer now! I would've never gone with the donut if these options were available for a comparable price for high power regulated psu (around 90$). the diy donut transformer journey was a long one and I do not recommend it.

Re MOT - seeing how transformers drop a lot in voltage when connected to load, I overvolted mine when load free such that when idle zvs is connected voltage drops back to around 55 volts. (overvolt was on the order of 15 V or so - quite a bit). This killed the fans by the way, connect them to external supply if you go that way). 

15
Hightemp:
Well, the way I see it, power output will determine how quickly you heat things up and WHERE the thermal equilibrium is reached - aka power IN starts being equal power OUT.
It is also determined by losses. Even if energy is pumped in at a slower rate, but you somehow can magically improve insulation, you will reach equilibrium at higher temperatures. The other thing to note is, exponentially more energy is required to raise something to a degree at higher temperatures than at lower temperatures (relative to outside temp that is). That fact was especially evident with my other-other pottery kiln which lights up an LED when SSR is on so it is easy to see the difference.

You can reliably melt about 3 kg s of copper with about 800 W. I will be doing further tests + casting via lost PLA method soon ish, will have real numbers. It is funny how i started thinking like a scrapper a bit - always checking if there is some copper laying around somewhere haha.
peterspaco: I nearly doubled the coil so it covers full crucible. Power stayed nearly the same, even decreased a bit. Frequency has halved. I think the only way to increase output is to change diameter that can't be done currently with my setup.
To kind of summarize it (correct me if i am wrong) but MORE power is drawn if we have:
Lesser coil diameter
More material inside the working volume
Higher frequency
Less turns in the coil

 

16
hightemp:
If insulation is outside then water will definitely boil in the coil not to mention that the water be stealing a lot of useful heat away. The previous setup with bricks was somewhat like that, before I had the fiber insulation

17
Peterspaco:
I might try the thinner insulation, but the one I have is quite amazing. May be losing some efficiency with a thinner one.
Idle current: looks like i forgot to record it with the latest setup. will have to get back with that.
Crucible wrapping is one thing i didnt think of. Will try that next!
I hope to cast bigger things so even a 3kg crucible is too small. I made a whole sword with aluminium when I ran my propane mini kiln!

 

18
^wow so much activity here!
Well, I managed to melt my first copper! so yay...
I rebuilt the PS with a powerful fan underneath, using the original box. It looks very neat.
But most importantly, insulation does miracles.

The data is the following:
845 g of copper melt in a graphite crucible (so-called "3kg-crucible" on ebay)
in about an hour with an output of just under 1kW.

the question is, how do I draw more power? I cant make the coil any smaller because of crucible+insulation being quite thick. I can have more turns. I was thinking, what if I do TWO coils, meshed together (not touching), turned the same direction.
Would that double the drawn power(some sort of principle of superposition)?

I plan to make aluminium bronze and cast a nice golden-looking dagger=)

Here are some pics:   

19
Beginners / Re: Teach your kids electronics
« on: April 27, 2019, 06:57:40 PM »
I work at a library and here we have not only SnapCircuits, Mbots, but also Arduino kits that can be checked out home. It may be for a bit older kids, but some do know basics of programming at a rather early age!
Also it is good to teach kids 3d design, it is a real useful skill. Lots of adults seem to have very little spatial awareness which i find kind of funny. Tinkercad for the win!

20
I finally made something that works...
Here is my somewhat new setup with all previous mistakes accounted  for (I had no idea what I was doing previously, hope that has changed haha)
a.k.a the guide to using unregulated power supply for maximum benefit!

1. I moved all my operations to my bench connecting directly to the stove outlet via a proper thick cable for high amps.
2.I finally found the sweet spot where to tap the transformer accounting for voltage sag. The idea is to overvolt it just enough so that when the unit is connected to IDLE coil voltage drops to fifty volts (the voltage that the unit is rated for).
3. While doing so, I burned both 24v fans, so now I am using external fans from a pc PS.
4. I managed to melt aluminium in about 50 mins, with a power output between 1700 to 1500 w, using my diy kiln enclosure from another project, for heat insulation. I can measure the power with ac meter from ebay which is super handy. It can only be used on the transformer AC side. Still waiting for shunt dc meter to arrive for unit -side measurements.
5. The setup is stable and nothing is too hot. The transformer is output is taken as two secondaries connected in parallel, sent to a pair of fifty-amp rectifier bridges, with heatsink immersed in water.   
6. I made a couple new coils. The five turn work coil makes the unit run between 40-50 kHz, as it is seen on the oscilloscope. As I understand, smaller coil means higher current, higher frequency of oscillation and potential higher energy draw.

I think I can finally do copper and cast something useful when the THERMAL blanket and the sleeve arrives.






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