So i have been looking at making a temperature controlled oil-bath.
I would like a single unit just for the purpose of heated oil-baths.
Preferable a unit that can be placed ontop of a hotplate to use the stirring function.
A stainless steel bowl or a SS cooking pan could be the vessel that holds the silicone oil and the cartridge heaters to heat the oil.
A temperature controller where i can set wanted temperature and that also shows current temperature on a display would be nice.
A K-type temp sensor connected to the controller that measure the oil temp.
Needed items:
Some SS cartridge heaters.
A Temp controller like MYPIN, Inkbird or similar with SSR output and K-type sensor input.
Temperature sensor, K-type is 0-400°C more than enough.
A SSR like DA25 or DA40.
There are nice cartridge heaters on auction sites, something like this one.
Maybe i need 2 of them so heating goes quick.
220 VAC 500 W Cartridge heater 10 x 120 mm, about 7.5 euros including shipping. https://www.ebay.com/itm/175302577964?epid=897593127&has...
This one had expensive shipping, can be found cheaper if look around a bit.
I have not figured out how to mount the cartridge heaters in the stainless steel coocking pot yet but i will come up with something.
An alternative could be a 2000W AC 50-220V 25A Adjustable Motor Speed Controller/ PWM Voltage Regulator connected to the cartridge heaters (and
230VAC).
But then i get no temp regulation, just a knob with 0-100% power.
And i still would need a temp sensor and a display for the temperature.
Well im going to keep my eyes open for a suitable stainless steel coocking pot that i can use.Rainwater - 31-5-2022 at 07:53
Finding a PID controller with PWM output gets expensive. Most of those controllers are not for temperature applications. A quick google found 80-200
usd.
An arduino shield(s) would be an easy way to go.
The relay required is a little more complicated and depends on your preferred method of powering your heater. Mains power needs a triac with zero volt
detection and a special ssr for proper operation.
Best to build your own as I could not find a ready made product.
Even if your heater is designed for ac, being a resistive load will make no difference.
Slap in rectifier and smoothing caps, fuses and thermal overload. You'll be good to to for less than $20
All the parts I listed are i2c interfaces with regular/logic shifters built in. $60 plus the controller.
More if you want perty circuit boards
Edit. Hit post to soon. The heating element you selected will not function by itself. It requires a precision fit into a heatsink. The heater is
simply not big enough to dissipate without additional surface area. And if operated at full power will most likely burn itself up. I suggest getting a
block of aluminum with atleast 100 cm² surface area. 5w per cm² facing your heated media is a good safety range.
[Edited on 31-5-2022 by Rainwater]Twospoons - 31-5-2022 at 12:24
For the heater look for an "immersion heater". That search term will bring up a range of portable and fixed heater elements designed for direct use in
liquids.
You don't need PWM output in your PID - most of them will do something like a 10 second cycle with variable on/off ratio, which will be just fine for
liquid thermal control. Just don't get too powerful a heater.
I would stick with a commercial PID controller like the one you've shown - going down the arduino route will be a lot more work. The commercial
controllers give you everything you need in one tidy package. Connect power, thermocouple and heater and you're done.
The SSR doesn't actually need to be 'zero-crossing' for a resistive load like a heater, but it will be less electrically noisy. I'd suggest you get
one from a reputable source like Mouser or Digikey, as there are a lot of fakes on Ebay, especially out of china. Re-marking a low power product to
look like a high power product is a common scam. And you wont know until it goes bang! I have some from China marked as 40A - I would trust them up to
about 1/4 of that.
[Edited on 31-5-2022 by Twospoons]Rainwater - 31-5-2022 at 15:56
Sorry, seen pwm controls and took off like a fat kid chasing the ice cream truckTwospoons - 31-5-2022 at 19:31
... and took off like a fat kid chasing the ice cream truck
Lol, priceless!
Back on topic, many of those PID controllers also have a separate alarm output, triggered by either under or over temp. It would be worth hooking that
up to a cut-out circuit or an audible alarm, just in case the SSR dies (they often fail shorted). Nobody wants an oil fire.Mateo_swe - 5-6-2022 at 02:15
Although i have some 32-bit development boards i would like to buy a plug and play solution.
The heating element could be a water heater i think, like in the pic.
Its 500W and i could just connect it to the SSR and 230VAC and use a PID temp controller.
I have some china SSRs, but i havent tested them yet, maybe they are low quality.
