Any particular reason for not using an SSR off a 5V line?
Not technically as far as I know, may be overkill though but if you have one try it.
The advantage of the L298N is that if you choose to use reverse pulse later it is set up for that purpose. A useful site for the L298N is: http://www.instructables.com/id/Ardu...otor-Controll/
The deciding factor is the switching rate; I use 200 cps at 50/50 on off ratio, but if you like experimenting you can go up to 30-50kps.
It seems there is no instruction or much literature out there for electroforming silver directly onto conductive paint treated surfaces. I have started now with the Cooksons Scandia 360 cyanide silver plating solution, working on an outside bench in a large tray and proper respirator mask, painters jumpsuit and gloves. Even though even the rinse baths are slightly alkaline you can still smell the cyanide fumes without a mask. I think, working with my chemist background, this is safe. The items, a flower and a mushroom, sprayed with conductive paint, came out with a bright grey matte coat, not shiny. They quickly turn yellow and darker, too at some places. There should be a plating time or 2 minutes per 1 micron, so I gave the items each 1 hour, which should be 30 microns.
The petals of the flower are stiffer, but not really enough to be taking any larger force like polishing. I left the item in one hour more and there is only small change, definitely not 60 microns! Because the plating solution is black, you can't see what is going on inside the beaker. I use 6 fine silver electrodes each 30g. The rectifier has been set to 1V and then to 0.01A/cm2, but the current is fluctuating a lot and it wasn't possible to increase it to the needed level of 0.9A for this item without turning the voltage knob up, too. This direct silver electroforming is very different to both copper electroforming and silver plating on a standard ring, I can say, so far. If anyone has tips? I suspect the electroforming times are much longer than the standard recommended plating times, so not 1 micron per 2 minutes. I suppose it is more similar to electroforming copper where you should have a lower current to start with and then increase and leave for hours? Right now I think, electroforming copper, nice and shiny and then silver plating is much easier. But is the resulting item fine jewellery or costume jewellery with so much copper? What are your ideas?
Just looked up the numbers in Electroforming; according to that, the deposition rate @ 0.5A per square decimetre (eww) in cyanide silver is about 19u per hour. 1A/sq decimetre it lists as approx 38u/hr at 100% efficiency.
The chart doesn't go beyond 5A/sq decimetre.
If your PSU is delivering fluctuating current that's unlikely to help things.
The electroformed silver remains porous, which means that articles which decompose, will also discolour it. On the whole, it is better to choose dried objects, which will dry again and form a matrix, however weak, for the piece formed.
There is little hope of polishing beyond say, brushing with a glass brush. Heavy deposition is at the expense of detail so except as a curiosity, I don't find much use for this process in jewellery making.
Thanks for the update!
I'd love to see your neighbours faces when they see you out and about with all your gear on!! As a chemist myself, I cant say I am as sanguine about the risks- your precautions are good but it is the mistakes/errors that hurt and with cyanide you only have 1 minute to save yourself.
Having not used the cyanide solutions I can't give expert advice, but from my reading about, I thought you needed to use a strike solution first and then electroplate over that. Also, do you have any agitation? That often helps things. Further to Dennis's note did you seal the objects first with an acrylic sealant?
WRT the finished product- if it is hand made and good quality then it as a piece of artwork, irrespective of the materials. Probably couldn't call it fine jewellery mind you.
Cheers Matt
Apologies for resurrecting this thread, but I can't seem to find any more info on what has been discussed here prior.
I am interested in building a pulse controller like the one described by John (555 timer based) or some alternative. Has anyone explored this further? I understand conceptually what the unit needs to do, but I am unsure of how to build it. Having experimented with pulse plating a bit, a small low cost DIY chopper circuit like this seems like it could be really handy.
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