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macckone
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That PID is really good price but the probe is a rip off.
The probe cost is already covered under the shipping, which is outrageous.
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wg48
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Quote: Originally posted by macckone  | That PID is really good price but the probe is a rip off.
The probe cost is already covered under the shipping, which is outrageous. |
Yes excellent price for the controller as it comes with a 40A SSR and heat sink. The heat sink looks small for a 40A SSR probably fine at 13A.
However judging by the suffix on the model number (from the pic) it’s a reverse controller which I think means when the temperature is low the
output is off/low. It needs to be high to drive that SSR.
The description for the controller states "the detective temperature range is 0- 400C" if correct its low for a tube
furnace.
Check the full model number against the spec for no surprises.
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Fulmen
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The most common PID's are limited to K-type elements and 400°C, but if you shop around you can find models that handle virtually any sensor. Here's
one:
https://www.ebay.co.uk/itm/TA4-RNR-Digital-LED-PID-Temperatu...
If in doubt, look for something like this:
| Quote: | | T/C Input: K: 0~1200°C; J: 0~1200°C; S: 0~1600°C; E: 0~1000°C |
If it's K-type only and no range listed it's probably a 400°C-model.
We're not banging rocks together here. We know how to put a man back together.
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wg48
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| Quote: Originally posted by NEMO-Chemistry | Triacs are used with AC, pref one with zero point crossing detection, that way you can safely switch upto 50 or 60 times a second (depending on
country).
I got a circuit for a pic micro with a decent triac switching circuit, its no big deal to swap out the pic for Arduino. |
It’s probably not worth the effort to construct a PID controller given the cost of the "off the shelf ones".
What we need is a ramp and soak PID with burst fire output. So you can ramp slowly to the soak temperature. The hard on until your almost at the
required temperature is tough on the furnace insulation and heating elements. Now that type of controller costs £100 and up. Ideally it would
interface to a cheap optical pyrometer or possibly a tungsten resistance temperature sensor ie a tungsten quarts tube lamp (my idea for a cheap
temperature sensor to say at least 1300C I hope)
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Fulmen
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Agreed. If you can build a cheaper/better ramp-soak controller that's one thing, but trying to compete with commercial PID's are pointless.
We're not banging rocks together here. We know how to put a man back together.
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yobbo II
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The probe cost is cheap (very) imo. I f you can find a Pt/Rh tc for anything like tho cost I would love to hear about it. Is it a good quality probe
though?
Some wire here, an outrageous price.
https://www.ebay.com/itm/Pt-Pt-Rh-wires-for-thermocouple/112...
Pt100 probes are not tc's btw, but a platinum resistor. No good for tube furnace.
I love the W filimentt probe. Sounds great!
Molybdenium elements are no good in air.
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macckone
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A K-type thermocouple will be just as good and much cheaper, If you
want to go above 1200C you are going to have to go with molybdenum
elements or something similarly exotic unless you go with direct flame.
And at that point you are also getting an exotic tube material, exotic
insulators and then the Pt/Pt-Rh makes sense. But you can get bare
wire way cheaper than that directly from omega engineering. Which
given the application may be a better choice than a sheathed probe.
RTD like PT100 or tungsten filament work fine for tube furnaces,
provided they have the correct substrate. Most of the PT100 are only
rated at 600C.
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yobbo II
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Afaik pt resistance devices only go to 900c or so
http://www.ni.com/tutorial/7115/en/
I may be wrong. Anyone got a source of reasonably priced pt100 type devices that go to 1200 or so?
When you say molybdenium i think you are referring to molybdenium disilicide.
Molybdenum is hopeless in air and more or less fails completely around 800c.
Molybdenum
This material was first used in industrial furnaces around 1930, with increasing usage
after 1940. It is available in a wide range of forms, with the most common element shapes
employed being wire, rod, strip, and on occasion, tubes.
This material has a strong affinity for oxygen at elevated temperatures and can only
be heated in the presence of a vacuum, reducing (dry hydrogen or cracked ammonia), or
pure inert atmosphere. Molybdenum starts to oxidize between 250 to 300°C with the
formation of molybdenum dioxide (MoO2) that will offer a limited amount of protection
against further oxidation up to around 600°C. At this point the molybdenum dioxide
converts to molybdenum trioxide (MoO3), which becomes dominant.
Molybdenum trioxide is very volatile and readily boils off, exposing the base metal
to further oxidation. At around 800°C catastrophic oxidation occurs with clouds of
molybdenum trioxide being generated. With respect to atmosphere purity, an argon...
Attached is stuff on heating elements.
Cant attach
http://www.thermcraftinc.com/electrical-resistance-heating-e...
Often wondered obout yittium oxide. It is available on ebay.
Where can i get cheap pt and pt/rh wire for thermocoupler cheap on omega? Their prices are outrageous.
OUTRAGEOUS!
[Edited on 15-11-2017 by yobbo II]
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Amoled
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Sorry for Inactivity, this thread look great, I will read through it this evening
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JJay
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Does anyone see a better deal on a PID controller than this one? https://www.ebay.com/itm/Universal-Temp-Controller-PID-w-SSR...
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