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Reclaiming Copper from Sodium Persulfate #4: 6B Pencil Lead Anode
As previously noted I’ve decided to give softer sketch pencil leads a try.
It looks like the electrodes are more efficient and a bit more stable. I’ve also noticed that the solution seemed to have taken on a lighter blue color and the copper cathode seems to have gotten thicker. In principle it seems to work!However, the thicker anode too started to disintegrate after a few hours at 2 to 2.1 V.
It’s time to go back to the drawing board and see if it would make sense to get either a properly manufactured graphite or coal electrode or even go all out and get a platinum one.

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Reclaiming Copper from Sodium Persulfate #4: 6B Pencil Lead Anode

As previously noted I’ve decided to give softer sketch pencil leads a try.

It looks like the electrodes are more efficient and a bit more stable. I’ve also noticed that the solution seemed to have taken on a lighter blue color and the copper cathode seems to have gotten thicker. In principle it seems to work!
However, the thicker anode too started to disintegrate after a few hours at 2 to 2.1 V.

It’s time to go back to the drawing board and see if it would make sense to get either a properly manufactured graphite or coal electrode or even go all out and get a platinum one.

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Reclaiming Copper from Sodium Persulfate #3: Bigger Graphite Anode

I tried scaling up the graphite anode by connecting several sketch pencil leads together.

I’ve done this using single strands of stranded copper wire to weave and knot the individual pencil leads together. Once tightly woven into place I’ve finalized everything by adding generous amounts of solder.

With regards to being able to use higher voltages this was no help (of course) and the pencil leads still disintegrated.

What I’ve learned:

  • Fellow hacker reloc pointed out that the softer a pencil lead, the more graphite it contains. I’ve picked 2H leads for my tests so far and will switch to 6B leads (the softest I could find at short notice).
  • What is going into solution depends on the voltage applied (potential) and which materials of lower potential are still there (if available, the lowest energy bond breaks first, even with high voltages).
  • Documented potentials (see: Pauling electronegativity) are usually defined for platinum electrodes. If you’re using something else, you have to apply a correction value. Also thanks to reloc for helping out with all the theoretical science behind the experiment!
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Reclaiming Copper from Sodium Persulfate #2: Stainless Steel Anode

I got my hands on some pieces of stainless steel to replace the graphite anode.

Reader’s Digest version: the mess got bigger. Green is the new blue.

What I’ve learned:

  • Stainless steel doesn’t seem to work well, the solution quickly turns green.
  • The green color could be Iron(II)-Sulfate, though that is not yet verified. Anyway it’s not really a success.
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Reclaiming Copper from Sodium Persulfate #1: The Naive Approach

At shackspace we’re somehow in the business of collecting sizable amounts of used up etching solution. We’re using Sodium Persulfate which on its own is also used as a bleach, detergent or disinfectant.
However, with plenty of copper ions in the used up solution it’s a very potent poison and you should not by any means pour it down your drain, ever.

A quick search on how to get rid of the stuff yielded Marc Schaffer's page (German) who explains his electrolysis setup using a 12 V 900 mA Photocell, a copper cathode and an anode made from either stainless steel, coal or platinum.

Platinum was no option because of its high price. I didn’t have any stainless steel that I could verify to be stainless steel at hand, so I opted for coal.
The closest thing to coal I could think of was graphite.
And since I’m a lazy person, I simply got some sketch pencil leads. All the core, none of the casing :)

The result of the first experiment can be seen in the pictures above:

  • The pencil lead disintegrated
  • A huge mess

What I’ve learned:

  • 12 V won’t work. Anything much higher than 2 V will cause the lead to disintegrate
  • Electrolysis should start at around 1.8 V, that’s when bubbles (Oxygen) start to form at the anode
  • Graphite particles can be filtered out quite easily using a piece of paper towel
  • More electrodes should have better yield
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Teardown: Water Flow-Sensor

Recently the shackspace lasercutter started to act up a bit. Turns out that I’ve probably put a bit too much copper sulfate into the cooling water and it started to react with the aluminium connector pieces which then corroded and closed up on themselves.

However, after having just cleaned them, the lasercutter complained again that there was no flow. So this time around I suspected the flow sensor itself. Turns out I was wrong (it was the just recently cleaned connectors, again) but I took apart and cleaned the flow sensor anyway.

The sensor itself is genius in its simple design. It has a single moving part: a small flap that blocks flow in one direction but lets it pass with close to zero force in the other. The flap position is then detected, I’m going out on a limb here, most likely using a hall sensor or something similar.

What I also found is a piece of horrible engineering.
One side had a connector screwed in, secured with Teflon tape and a small O-ring. The O-ring was pressed to the casing by the face of the screw-in connector tube. So as soon as you start fastening the connector, the O-ring will inadvertently end up being squeezed into the tube and bunch up there, restricting flow and doing actually a worse job with water proving than if it simply wasn’t there at all.

Long story short, I’ve left out the O-ring entirely, put everything back together and it worked beautifully.

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Project Fronius Repair #5: No More Smoke!
After I posted a call for help to the shackspace mailinglist, asking for someone who owns or knows someone who owns a similar welding machine to take a peek at, chris suggested to just give Fronius a call.He even went one step further and actually called Fronius Germany!
From Fronius Germany he got a digital copy of the manual, troubleshooting guide and a high-level wiring diagram. While the latter did help in identifying the two stray wires, it didn’t help much in figuring out where they should be connected to.
Fronius Germany was also not able to give out any more details circuit diagrams or repair tips, since they only handle replacements.
This didn’t stop chris. He called up Fronius Austria and ended up talking to a very kind technician who offered to identify blown parts if we send him a photo (the resistor I couldn’t ID turned out to be 33 Ohm 5 W) and in the end sent a photo himself showing how to connect the two stray wires!
I already had a hunch that one wire had to be connected in an H-Bridge fashion since it was part of a pair, both connected to a transformer. The Fronius technician verified that hunch.
Cautiously turning on the machine for the first time after repairing bits and pieces here and there I was half expecting it to blow up again.Nothing of the sort happened! The machine booted up nicely and I could toy around with the settings on the front panel.
So far I’ve not had any of the torches or the water cooling system connected. I’ll do that once I’ve got someone with me who knows how the machine is supposed to operate to verify all is in order :)
So far it’s looking good!

follvalsch:

Project Fronius Repair #5: No More Smoke!

After I posted a call for help to the shackspace mailinglist, asking for someone who owns or knows someone who owns a similar welding machine to take a peek at, chris suggested to just give Fronius a call.
He even went one step further and actually called Fronius Germany!

From Fronius Germany he got a digital copy of the manual, troubleshooting guide and a high-level wiring diagram. While the latter did help in identifying the two stray wires, it didn’t help much in figuring out where they should be connected to.

Fronius Germany was also not able to give out any more details circuit diagrams or repair tips, since they only handle replacements.

This didn’t stop chris. He called up Fronius Austria and ended up talking to a very kind technician who offered to identify blown parts if we send him a photo (the resistor I couldn’t ID turned out to be 33 Ohm 5 W) and in the end sent a photo himself showing how to connect the two stray wires!

I already had a hunch that one wire had to be connected in an H-Bridge fashion since it was part of a pair, both connected to a transformer. The Fronius technician verified that hunch.

Cautiously turning on the machine for the first time after repairing bits and pieces here and there I was half expecting it to blow up again.
Nothing of the sort happened! The machine booted up nicely and I could toy around with the settings on the front panel.

So far I’ve not had any of the torches or the water cooling system connected. I’ll do that once I’ve got someone with me who knows how the machine is supposed to operate to verify all is in order :)

So far it’s looking good!

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shackspace Infrastructure: Laser Exhaust Fix

The shackspace laser cutter had a bit of a suction problem. The low pressure side of the big air pump connecting the pump to the cutter was soft and unstable and fell in on itself when the pump was running.

I’ve replaced the tube with a big flexible clothing dryer tube and got an angle and reduction piece to connect the lower diameter high pressure side to the exhaust going out of the building.

With help of dritter I then mounted the pump itself on the underside of the laser cutter table to clean up the mess under the table a bit.

Works like a charm and suction power is greatly increased.

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Project INFRA #5: Light Barrier Breakout

A few weeks ago I decided it’s time to build a small breakout board for the EE-SW1070. I also decided to try out OSH-Park to order the boards.

The results are most excellent! I’m very pleased with how the boards turned out.
The price was reasonable bordering on low. However, the low priority international shipping did take around three weeks. But you get what you pay for :)

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Experiment: Resonant Inductive Coupling

Because the automatic drip irrigation system on the balcony needed power - at least some of the time - I decided to do some quick and dirty experimentation with resonant inductive coupling.

The basic idea is to have two coils of similar dimension (the simple case).
Drive one coil with an AC signal - in my case this was done using a function generator and hold the second coil close to it.
For optimal power transfer, make sure the receiver coil is resonating at the frequency you’re using to drive the sender coil.

The most difficult part if you don’t have to have a LCR meter at hand, is finding out the inductance of your - probably - hand-made coils. Luckily there’s several methods to measure this if you happen to have some other tools at hand. I’ve used method two outlined in this handy howto.

To design the resonator circuit for the receiver, there’s also a nifty little calculator.

I somehow didn’t manager to get this setup to drive a LED on the receiver end, but that might be down to either too little drive strength or me screwing up the receiver circuit. Probably the latter.

However, I was able to get a nice strong coupling at least on signal level when measuring it with my scope.