About Nichrome Wire

If you're still in the stubby pencil phase, you might want to hop over to

and d/l their WireTronic app. It's a free, handy tool that collects various wire characteristics in one place and does include info on nichrome and other resistance wires.

--
Rich Webb     Norfolk, VA

We are talking about etching metal which generally means any metal device will be ruined. FeCl is like water(after all, you mix it with part water) but cannot be contained in any metals(maybe some alloys and stuff like titanium but not sure). AFAIK the only two methods of effective and efficient heat distribution would either require metal, which is out of the question here, or ceramics. Plastics are probably not an option. Of course I know very little about any specifics so there might be something out there that works. Glass is something that generally works(is glass classified as a ceramic?) and is used but it would be hard for D to make something out of glass that works well I'd imagine.

Yup..

Alternatively.... I just tripped upon Kanthal wire in my Google travels.

1) Forms a protective layer of aluminum oxide. 2) Used in heating elements.

Seems like I can tightly coil Kanthal wire without separators or adding an insulator.

Well, there IS, but it isn't insulating against electrons.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

Is it Chromium oxide?

With Kanthal you can melt the copper off the board :-) One of my projects for the future include a heat treating furnace for hardening and tempering tool steels. I would need fire brick, Kanthal wire, and a temperature control. IIRC, I've seen Kanthal heating elements for ceramic kilns on eBay before. It is high temperature wire but I'm not sure how you are going to transfer the heat to the etching solution. Is your pump going to pump the solution through tubing through heating elements? Are you going to have the heating element in a glass tube going through the solution?

One idea is that you could study the principle behind the instant hot water heaters and see if you can apply to etching solution. You don't have to use heating element wire, anything that converts electricity to heat should work, like a linear voltage regulator and a load resistor, use etchant running through tubing to cool the regulator and power resistor. For quick heating you would probably need something with a lot of surface contact area, maybe make something like a steam engine boiler using glass and/or plastic tubing.

RogerN

I plan on putting a 20cm long heating coil in a 6mm dia glass tube in a 15mm dia PVC etchant pipe. My construction is loosely based on an automotive block heater Example:

If I spend more time on research, I'll have to make and sell these heaters on Ebay. :P

Ya- not a renouned conductor, but like stainless steel, it's not very thick, so it still looks like metal. After using it in a kiln, say, it might be thicker and a fair insulator (but it'll also be brittle and useless).

Incidentially, most inorganic salts (like Cr2O3) become ionic conductors at about half their melting point, so hot nichrome is probably a fair conductor even if it's in good condition.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

Nichrome wire isn't likely to survive for very long in direct contact with FeCl, either; especially if thee is a potential difference between the ends. You need a ceramic or glass-encased element of some sort; but they are poor thermal conductors,so, for the same heat transfer as direct metal contact, you will need a much greater surface area or a higher temperature at the resistance element.

I believe Corning used to make waterproof ceramic heating elements, so that might be a direction to follow.

--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

What about a halogen lamp tube (the linear type, usually about 4" long). Then you only have to insulate the ends etc.

They are only a few $$ each. You could even build a "reverse Liebig condenser" arrangement to house it.

Sounds interesting, kind of difficult but interesting!

Anyway, one of my favorite suppliers for that sort of stuff is McMaster Carr. IIRC they have glass tubing, nichrome wire, ceramics, mica insulators, PVC tubing, and all sorts of industrial supplies. Their price is generally fair, they ship fast, and their stuff is almost always in stock.

I've been playing with temperature controls and such lately, I have an Allen Bradley PLC 5 programmed to control my electric smoker. Some info that may be of interest to you. DigiKey sells a 100 Ohm (100 Ohm at 0 Deg. C)platinum RTD temperature sensor for $13.XX. From what I've been reading the instrumentation for such, take a 1ma current source to power the RTD (More current heats RTD more). Also supply a 100 ohm precision resistor with 1ma. The voltage drop difference would be due to the temperature above

0 deg. C. Then an adjustable comparator for setting temperature to drive perhaps a solid state relay. An amplifier to detect rate of change can help with overshoot/undershoot. A few years back I bought a lot of 11 Fuji temperature controls that read thermocouples or RTD's and drive SSR's, the lot of 11 controls cost some $130 or so. You might want to check out Ebay temperature controls after you find out what a headache manual control will be.

RogerN

Why not just go to the aquarium store and get a glass-enclosed tank heater?

Tropical aquaria use sea water, which is also quite corrosive, so I hear.

Or is this more of a training exercise?

Good Luck! Rich

"What are the characteristics of Hastelloy C-276?

• Excellent corrosion resistance in reducing environments * Exceptional resistance to strong solutions of oxidizing salts, such as ferric and cupric chlorides ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Or he could just take a regular old calrod swaged element, slip it through an everyday piece of titanium tubing from the junk box and bend it into a "U". The top ends don't get immersed in the etchant. Ti is better than Hastelloy for resistance to FeCl.

Please don't etch your own PCBs - you're sure to want double/multiple layer boards really soon and at that point you'll send them out to pros, possibly wondering what ever happened to all those noxious chemicals you poured down the drain before you wised up.

The chemicals are in my coffee, dammit!

-- Joe

I used all my titanium scrap on my jet-pack. Would 24K gold tubing work instead?

-- Joe

Like a block heater..

Geesh...Who doesn't have titanium tubes in their junk box..

The worst for me is leak proofing.

I suspect my pcb's will be etched by the time I need to make a manual temperature adjustment. However electronic control would be nice.. There is a danger of vaporizing the etchant.

But yeah.. I'll watch ebay if I need a controller.

Interesting... Hastelloy tubes for the etchant plumbing. Might be extra $$$ if I don't like using ~$3 of PVC from the hardware store.