About Nichrome Wire

"D from BC"

..... Phil

There are cartridge heaters, band heaters, all kinds of heating elements. How about a power resistor in a glass tube? What are your requirements? Are you pumping etchant and need it heated in a tube? Lots of possibilities!

RogerN

No, generally they are put in ceramics to help distribute the heat for such things. If you can get some high temp coatings you might be able to use them. I assume by "etcher" you mean heating up the ferric chloride? If so then in I imagine you will still need some type of coating as it might be etched along with your pcb. I tried an "aquarium bubbler" thingamajig that was made out of sand and it was etched along with the pcb too... Well, at least some reaction or something took place. It didn't completely ruin it but screwed it up a little. Similarly I used an aquarium heater and the coating on it was partially etched(something in the paint I guess).

You might be able to use something like plaster of paris(try to etch a little and see if it reacts in any negative way just in case). A thin coating would probably work or you could make a brick or plate with the wire ran though it in some space filling pattern.

Stick with the aquarium heaters, they work great and they are cheap. Just go to the local pet shop. There are electronic thermostat submersibles that would work fine for etching. (just don?t submerge them ;))

Cheers

Titanium can be used for some etchants, but the $25 glass aquarium heaters are probably your best bet for something you can buy easily and will be safe.

Best regards, Spehro Pefhany

I got one of those 25$ ones, one of the higher power models. It was not enough to really get the etchant hot. It got it lukewarm. Of course over time it would get hotter but generally you don't wanna spend 30 mins just to heat the stuff up(as you can do it cold in 30 mins).

Cartridge heaters are in stainless steel. I can't remember which etchants don't etch stainless.

The etchant is pumped.

Target temperature is 40C to 55C. Time of temp rise: Say 10 minutes Starting temp: 23C Total etchant volume: 300ml (It's a tiny foutain type.)

I don't have heat capacity for ferric choride, Ammonium P. or Cupric Chloride. Assuming of heat capacity of etchant >water:

Then

Specific heat of water = 4.2 J/(K*g) m= mass= 1g/mL *300mL = 300g

q = 300g x 4.2 x (55C - 23C) = 40320 Joules

Energy = power * time

So...I need greater than 67 watts due to heat loss and using the wrong heat capacity.

Probably double that.. Say 134Watts. More power would be nice to reduce warm up time.

On Nov 22, 11:16=A0pm, D from BC wrote: (heater stuff mostly snipped...)

Two commercial sites for products I've used in the past:

or you might try Grainger, if they ship to your locale. They have a wide range of heating products. What about either a warming plate for keeping cups of coffee hot or heater tape used to keep pipes from freezing? None of these suggestions are cheap though...

I'm thinking of coiling nichrome wire in a glass tube to insert in the pump line. I'm jabbing it into the pump line like I'm doing voodoo on it.

The problem is insulating the nichrome coil such that turnings don't short. This is not a problem if the coil naturally stretches out a bit. But needling the nichrome wire through the center of the coil needs insulation (capillary tube,woven glass sleeve,maybe teflon tubing) which I haven't found yet (without buying a case load.)

The construction is like a long very hot radial leaded inductor.

Pass the liquid through a container with an electric kettle element.

Having an over-sized element like that won't cause too many problems unless you want really fine temperature control. The thermal capacity of the water is much greater than the thermal capacity of the heating element, so provided your controller has a wide enough proportional band, it won't overshoot and hunt.

We are not talking about water here...

So you want to do everything yourself? You can wrap the NC wire around an insulator (like a piece of glass) so that it's not touching itself, then insulate it with furnace cement (refractory cement). You should be able to find this at a hardware store; it's used to patch bricks in fireplaces and chimineys. Once dry it will hold everything in place. You'll still need to waterproof this heater if you're going to insert it into the etchant tank. You can also wrap the NC wire (again, don't let the coils touch) around a glass tube the etchant is passing through, then coat it in furnace cement to hold the wire in place and insulate them. Can you calculate how much current/voltage you will need? How will you measure/control the temp?

So you want to do everything yourself? You can wrap the NC wire around an insulator (like a piece of glass) so that it's not touching itself, then insulate it with furnace cement (refractory cement). You should be able to find this at a hardware store; it's used to patch bricks in fireplaces and chimineys. Once dry it will hold everything in place. You'll still need to waterproof this heater if you're going to insert it into the etchant tank. You can also wrap the NC wire (again, don't let the coils touch) around a glass tube the etchant is passing through, then coat it in furnace cement to hold the wire in place and insulate them. Can you calculate how much current/voltage you will need? How will you measure/control the temp?

• Why not use a ready-made wirewound resistor, or a string of them? ... then varnishing the wire or whatever they do to insulate adjacent turns has already been done for you.

Chris

I estimate about 200W-300W is needed to raise 300mL of pumped etchant to a temperature of 50C within 10 minutes.

At this power, I'd probably use the 120VAC here and control the heater with a light dimmer ghetto style.

I'll be selecting coil and wire dimensions to get 200Watts spread over as much surface area as my design allows. In my case, a NC ribbon coiled in a 5mm dia glass tube that is 18cm long.

ugh.. T regulation.. For now, I'll control the temperature manually. (Turn dimmer dial + IR probe) :( I'll design a thermostat with thermocouple at a later time.

I suspect I need a red hot nichrome heating element. Kinda like putting a pot of cold water on a red hot stove element.. It still takes awhile to reach a boil.

I made a Nichrome Plexiglas bender once. It lengthens significantly when hot. So I mounted it on ceramic stand-offs... one end fixed, one end spring-loaded to maintain it straight. ...Jim Thompson

Ha.. Perhaps call it speaking in links.. I get the picture. :)

Thanks

Is this primarily water-based or is it an organic fluid? If the former, it will behave thermally like water - if the latter, your insulating problems will be a lot simpler but you might need to duplicate the thermostat with a second overheating cut-out.