End of September update: progress has been made on a number of fronts!
I discussed the auto-fill circuit with a friend who is an electrical engineer. He agrees that in theory at least, an AC circuit is better than DC for this application: "The only potential drawback over an 'AC' based capacitance system is that the probe is always positive and the pot is always negative". In practice however, a DC circuit can be made to work with little or no compromise by limiting the current that passes through it. His suggestion is to use a bipolar transistor which, depending on the components, should limit the current to 1 or 2 uA. Lowering the duty cycle to 1ms per second by strobing the power to the probe may or may not be necessary. In any case, once a layer of scale builds up on the inside of the boiler, all electrolysis bets are off. To be continued when I get around to buying the required parts!
Something much more exciting: after a long delay because of things getting lost in the post, the POWDER COAT PAINT ARRIVED!
Time to build a paint stand! Two cross bars with pins to fit the holes on the top of the cover:
...and a pair of U-shaped legs formed with the bender.
Some quick welds...
...and the stand is done.
Unfortunately, I don't have much documentation of the actual powder coat process. I did it at a friend's shop and it was a bit of a mad rush. Also, because he is set up to paint smaller things, applying the powder took four hands, leaving none for the camera. As with most painting, the hard part is the preparation - you know, Saturday afternoon you decide to paint the living room. First you move out all the stuff: the couch, the tv, 10 years of magazines you never read etc., then it's cleaning and putting masking tape on all the trim and every last switch and electrical outlet, then Sunday just after Home Depot closes you realize you forgot to wash the &*^*%$ing roller and brushes last time so now your whole house is upside down until you have another free weekend... Can you tell I love painting?
Prepping for powder coat is still arduous, but the end result is so much more satifying. First, I sanded the entire inside and outside of the cover to remove every last trace of rust. Then, the part has to be completely de-greased. I started with a commercial water-based de-greaser and then finished with 99% isopropyl alcohol. Then it's into the oven so that the metal can off-gas. As this is mild steel, it turned a pretty color after what is essentially also an annealing process.
Applying the powder itself relies on creating opposing electrostatic charges between the paint particles and the part itself.
After application the part goes back into the oven to melt the polyester resin so that it forms a permanent bond with the substrate.
The date on the first drawing for the cover is the 4th of February 2017. So after eight months and twenty more minutes in the oven, this part is DONE! I think that we might just be starting to see some light at the end of this tunnel.
I discussed the auto-fill circuit with a friend who is an electrical engineer. He agrees that in theory at least, an AC circuit is better than DC for this application: "The only potential drawback over an 'AC' based capacitance system is that the probe is always positive and the pot is always negative". In practice however, a DC circuit can be made to work with little or no compromise by limiting the current that passes through it. His suggestion is to use a bipolar transistor which, depending on the components, should limit the current to 1 or 2 uA. Lowering the duty cycle to 1ms per second by strobing the power to the probe may or may not be necessary. In any case, once a layer of scale builds up on the inside of the boiler, all electrolysis bets are off. To be continued when I get around to buying the required parts!
Something much more exciting: after a long delay because of things getting lost in the post, the POWDER COAT PAINT ARRIVED!
Time to build a paint stand! Two cross bars with pins to fit the holes on the top of the cover:
...and a pair of U-shaped legs formed with the bender.
Some quick welds...
...and the stand is done.
Unfortunately, I don't have much documentation of the actual powder coat process. I did it at a friend's shop and it was a bit of a mad rush. Also, because he is set up to paint smaller things, applying the powder took four hands, leaving none for the camera. As with most painting, the hard part is the preparation - you know, Saturday afternoon you decide to paint the living room. First you move out all the stuff: the couch, the tv, 10 years of magazines you never read etc., then it's cleaning and putting masking tape on all the trim and every last switch and electrical outlet, then Sunday just after Home Depot closes you realize you forgot to wash the &*^*%$ing roller and brushes last time so now your whole house is upside down until you have another free weekend... Can you tell I love painting?
Prepping for powder coat is still arduous, but the end result is so much more satifying. First, I sanded the entire inside and outside of the cover to remove every last trace of rust. Then, the part has to be completely de-greased. I started with a commercial water-based de-greaser and then finished with 99% isopropyl alcohol. Then it's into the oven so that the metal can off-gas. As this is mild steel, it turned a pretty color after what is essentially also an annealing process.
Applying the powder itself relies on creating opposing electrostatic charges between the paint particles and the part itself.
After application the part goes back into the oven to melt the polyester resin so that it forms a permanent bond with the substrate.
The date on the first drawing for the cover is the 4th of February 2017. So after eight months and twenty more minutes in the oven, this part is DONE! I think that we might just be starting to see some light at the end of this tunnel.
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