PDA

View Full Version : Need some ideas... Building a small 110v project oven (225* fahrenheit)



Taiden
11-07-2010, 08:58 AM
Hey all,

I need to build a 2' x 1.5' x 1.5' project oven that holds a 225* temp and plugs into a 110v socket.

I'm in the planning stages so I need some ideas on:

1) heating element
2) temperature control
3) insulation material?
4) outer structural material



The ideas I had were:

1) 110v adjustable hot plate (for boiling water etc)
2) the adjustability might take care of this, but not sure what to do if it doesn't. thermostatic 110v switch?
3) I have no idea...
4) naturally I want to weld something up, so maybe 14 gauge mild steel sheet?

welderShane
11-07-2010, 09:19 AM
Whats its for, powder coating?

digitalman2112
11-07-2010, 09:27 AM
Sounds like a powdercoating oven - there are lots of plans online. Most that I've seen at that size use the heating element, and controls from a scrap kitchen range / oven. Given the low temperature you need and the small size, I'm thinking you might also be able to get away with a toaster oven element / control provided it was well insulated.

This build (http://machinebuilders.net/plans/gallery/Big%20Kids/PowerCoat%20Oven1.pdf) has excellent detail on design considerations and construction methods.He spent $300, but yours is much smaller, so you should be able to cut the cost...

wskynajar
11-07-2010, 09:30 AM
Taiden....You could go to wal-mart an pick up one of those toaster-ovens, for like $25 or$30 bucks an redo as you needed.You would have a heating element, thermostat, an even a timer. Thats just one idea.

wskynajar
11-07-2010, 09:31 AM
lol....i was a little late on the typeing.

Taiden
11-07-2010, 09:43 AM
actually it's for heating up headlights, I do HID retrofits and I heat them up to soften the OEM sealant so I dont crack the lenses trying to open them. :)

That's why no hot spots are important, I can't afford to melt any plastic.

Can you powdercoat at 225 fahrenheit? If so, it looks like I might have a multipurpose machine :D

Taiden
11-07-2010, 09:49 AM
Oh, I'm a big fan of the toaster oven idea... I bet I could find a used one kicking around in a good will or something. :D

jpump5
11-07-2010, 09:52 AM
Toaster oven.You probably won't even have to buy one.People throw them out all the time because they
are dirty.I built an electric smoker out of one.
Is this project temperature critical?
You may want to monitor the temp. with something else(multimeter w/thermocouple probe,etc.)
at least until you can verify temp. settings.

towel
11-07-2010, 09:53 AM
Throw some wood chips and meat in it and you have yourself a smoker.

jpump5
11-07-2010, 09:55 AM
Oops- more slow typing

Taiden
11-07-2010, 09:58 AM
temp should be between 200* - 225*, never exceeding 250*

HundredaireSocialite
11-07-2010, 11:31 AM
Sounds like a cool project.

For powder coating you need around 350-400. I've got a little toaster oven (out of the trash, of course) that does that easily.

I've also got an actual kitchen oven, (also out of the trash) that works fairly well for powder coating. It's a little small for the things I want to start powder coating, but at least it's bigger than my toaster oven. It would work pretty well for a couple of headlights.

I'm going to be building my own oven for powder coating as soon as time/space/money/necessity/planetary alignment allows.

Some of the ideas I've come across online consist of using concrete backer board for the walls, metal studs for the frame, and either fiberglass insulation and or that blue insulation foam that's sold in sheets.

Anyway, a little toaster oven will do about 500*. If you take the heating elements and controls and put them in a box that's 2'x1.5'x1.5', I bet you'll get your 200*-225* temp range easily.

Whatever you do, let us know how it turns out.

turbocad6
11-07-2010, 11:59 AM
I've done a lot of headlight retrofits & personally am not much of a fan of the oven method... it puts too much heat into the other components & if your not real careful you will wind up with discoloration or even micro crazing of the lenses among other problems like inner fulcrums & pivots becoming brittle, man times the heat damage doesn't even show itself until your done & put the light back into service...

I use a heat gun & pass it over the seem continually, keep it moving & put enough heat into it to heat soak the seam enough to soften the sealer... average headlight takes all of ~4 minutes to open without damaging anything... the amount of effort you'd put into perfecting an oven technique isn't worth it unless your planning on doing huge volumes like cincity or something, I'd suggest trying a good heatgun first...

Sandy
11-07-2010, 12:02 PM
Keep in mind that cookin oven and toaster oven temperatures are "average overall'. The heat up pretty high then shut down and let temps drop quite aways before turning back on again, plus the temps at the top can be quite a bit higher than temps at the bottom.

In short I'd question whether their regulation is accurate enough for critical work.

Taiden
11-07-2010, 12:25 PM
I've done a lot of headlight retrofits & personally am not much of a fan of the oven method... it puts too much heat into the other components & if your not real careful you will wind up with discoloration or even micro crazing of the lenses among other problems like inner fulcrums & pivots becoming brittle, man times the heat damage doesn't even show itself until your done & put the light back into service...

I use a heat gun & pass it over the seem continually, keep it moving & put enough heat into it to heat soak the seam enough to soften the sealer... average headlight takes all of ~4 minutes to open without damaging anything... the amount of effort you'd put into perfecting an oven technique isn't worth it unless your planning on doing huge volumes like cincity or something, I'd suggest trying a good heatgun first...

it might just be a preference thing. i'm coming up on my 14th pair of headlights opened, and so far I prefer the oven method. I've done the heat gun method on probably five and while it works, and is more portable, I would find it much easier to use an oven. :)

turbocad6
11-07-2010, 12:31 PM
what headlights do you specialize in? or do you do many different types? personally I do mostly infiniti fx headlights, been doing a dual projector modification on these, I even built a vacuum chamber for mold making & cast my own clear side marker reflectors which turned into a huge pita... I'd like to see some of what your doing in there :)

HundredaireSocialite
11-07-2010, 02:05 PM
Keep in mind that cookin oven and toaster oven temperatures are "average overall'. The heat up pretty high then shut down and let temps drop quite aways before turning back on again, plus the temps at the top can be quite a bit higher than temps at the bottom.

In short I'd question whether their regulation is accurate enough for critical work.

Maybe that's why my powder coating always comes out so bad.:laugh:

I'll have to look into alternatives.

weldbead
11-07-2010, 05:05 PM
i know you wanna weld up a box...and maybe im crazy...but if its only going to 250 degrees make it out of wood, which is an insulator and burns at over 400 deg

Taiden
11-07-2010, 07:52 PM
i know you wanna weld up a box...and maybe im crazy...but if its only going to 250 degrees make it out of wood, which is an insulator and burns at over 400 deg

I had this thought too... but I'm thinking that the element will get much hotter than 250 degrees. and I wouldn't want it to burn anything.

joefitz
11-07-2010, 08:08 PM
This might be a piss poor idea, but if you need it to be a specific temperature... Say 225F and leave it there and not worry about it fluctuating temperatures too much you should use something that absorbs heat easier than air and will stay where you leave it. Do a couple of experiments with a hot plate and control the hot plate with a thermostat in the water....

Then you'd eliminate the chances of hot spots and be able to clean off the headlight assembly easily.

If this doesnt make sense it's because I'm exhausted

-Joe

cantthink
11-07-2010, 09:36 PM
not much useful input on the other stuff, but if you want to avoid / reduce hot spots.....a circulating fan might help distribute the heat by mixing the air in the oven. my toaster oven has this....makes a killer grilled cheese ;)

jreynoldswelding
11-07-2010, 09:51 PM
Looks for a used camper oven. Or look for a big toaster oven.

Knotbored
11-08-2010, 09:48 AM
Convection ovens use a fan to circulate air in the oven, and those are/were used in more expensive homes that tend to throw out useful apliances before they wear out.
(the only difference between a normal and a convection oven is that fan)

kb0thn
11-08-2010, 09:56 AM
Here is an oven I built for potting electronics:
http://www.aprsworld.com/gallery/shop/IMG_7386

$40 Target toaster oven. Stripped out the control electronics and replaced with a PID controller and solid state relay.

pyroracing85
11-08-2010, 11:46 AM
If you have it I would go to 220-240 volts save the amps. What wattage element do you plan on using?

Oh wait you need help on that.

Sorry, I dont know any companies that make them.

Taiden
11-08-2010, 12:43 PM
Hey kb0thn, that's amazing. Do you have a link to a build thread on that?

I was looking at PID controllers online and they seem to all be upwards of $200.

I'm trying to spend less than $100 when all is said and done.

Do the PID controllers use PWM to control temps instead of using an on/off thermostatic switch? Seems like that paired with a convection fan inside the oven would make for pretty darn accurate temperatures.

slopecarver
12-02-2010, 02:36 PM
PID controllers use a relay to turn on and off a heating element of air conditioning, in terms of a heater it may cycle on for 1/10 of a sec and be off for 9/10 of a second. The PID controller varies these times to achieve a steady temperature, longer cycles for a larger heated environment.
3 things for a controller than can keep an oven at 225+-.1F for ~$50:
Sestos PID Controller on eBay
25 amp Solid State Relay on eBay
pt100 Thermistor on eBay
These exact components can be used as part of a sous vide (http://en.wikipedia.org/wiki/Sous-vide) cooker as well
http://cgi.ebay.com/New-PID-Digital-Temperature-control-Controller-100-240V-/320625525508?pt=LH_DefaultDomain_0&hash=item4aa6c54304
http://t0.gstatic.com/images?q=tbn:ANd9GcSoz23MZ3SzblYTvlLyOmSoo4-h_RMgeMP-RnNsBzpPb6qvBvZrWw
http://cgi.ebay.com/SSR25A-SOLID-STATE-RELAY-PID-Temperature-Controller-/110616576129?pt=LH_DefaultDomain_0&hash=item19c1430081
http://t2.gstatic.com/images?q=tbn:ANd9GcQ_b_Za0csdtoHAMzTFGIeNDMym3lc9D NKqZVrPLEHg4URdOiZJKw
http://cgi.ebay.com/Thermocouple-Temperature-Control-Sensor-Probe-PT100-1m-/260700903671?pt=LH_DefaultDomain_0&hash=item3cb2fc18f7
http://www.cdautomation.co.uk/images/product/70.jpg

I would make a temperature controller box that you can plug anything (brew heater, sous vide, powdercoat oven, smoker...) into along with the temp probe and therefore control its temp exactly. this PID controller has an auto-tuning function

Taiden
12-02-2010, 02:55 PM
slopecarver, before I bid on these items (im' about to whip out the paypal account since you sent those links) I have a few questions

1) could I build the controller so its just inline with the wall socket plug for my toaster oven, then fish the thermocouple inside

2) is that PID controller the right one? It says it has 1 relay output, they have another model that has 1 solid state relay output. would I want the SSR output one instead?

3) do you have any suggestions for materials for making the enclosure?

rudytj
12-02-2010, 05:32 PM
would 212 degrees be close enough? would it be possible to do something on a double boiler idea where the you heat water in the outer vessle and heat your headlight in the inner vessle? no need for complicated circuits etc just need to remember to add water.

Taiden
12-02-2010, 06:01 PM
I thought about that, the only issue is I really do not want to do it because headlights have to be dry when you reseal them, and the oven will be used to reseal them. introducing any kinds of moisture early on will increase the chance of fogging issues for customers later down the road.

turbocad6
12-02-2010, 06:41 PM
just a side note now that you mention moisture, but it's a really good idea to pick up some tiny desiccant dryer packs, the kind used in shipping & packing to eliminate moisture damage & glue one or 2 inside each headlight... a little moisture buildup can be almost normal & the desiccant dryer packs will absorb it & not let the lenses fog up at all, it's self renewing from the heat in use... just a little trick some of the bigger headlight guys have picked up on...

Taiden
12-02-2010, 06:47 PM
yeah, i currently use desiccant packs as a backup plan... but the less moisture i start with, the happier I am. :)

Meat man
12-02-2010, 07:55 PM
Watch out for the hot plate idea. I used one in a smoker and I melted the plastic bits out of it. An old school, all metal one would be OK, but new ones won't last.

I ended up canibalizing an old 220v stove for the oven elements and the top burner. I chopped out the stove top that holds the burner and used high-temp wire (from appliance repair store) to rewire it. I re-used the stove knob for the round burner. Purchased a thermostat to run the oven element for a majority of the heat.

This will run 110v also. Works pretty well.


http://www.alliedkenco.com/catalog/product_info.php/cPath/89_86_87/products_id/781

rlitman
12-02-2010, 07:55 PM
I thought about that, the only issue is I really do not want to do it because headlights have to be dry when you reseal them, and the oven will be used to reseal them. introducing any kinds of moisture early on will increase the chance of fogging issues for customers later down the road.

The water boiling idea could be a good one. You just need to seal the double boiler, and vent the steam away from the headlight. I use a similar double boiler for melting chocolate (which is just as sensitive to any moisture), and although I don't get anywhere near boiling temperatures, the water jacket will guarantee no hot spots.

A toaster oven is good to raid for parts (mostly the heating element), but you will get wide temperature variations (think about how uneven your toast browns), and anywhere your toast gets brown, plastic would too. You could build a metal box, with the heating elements on the outside, and line the box with ceramic tiles. The problem, is that if any surface (like the element) is significantly above your safe limit, its radiative heating can raise surface temperatures in view of it, to just about that level.

slopecarver
12-02-2010, 11:46 PM
That PID controller has a SSR(Solid State Relay) inside, however it is only rated at 3 amps (it takes circuit board voltage and ramps it up to something more usable which could directly control something of a lighter duty, not a 1000W+ heater, for that you need another SSR rated for more amps. For the enclosure just weld up a box, you have those capabilities correct? :p

The assembly would be built into a project box of some sort. plug the assembly into the wall, plug the heater and thermistor into the assembly. I say plug the thermistor into the assembly because you could wire it to a stereo headphone jack and wire a port into the box. Not shown on the back of the box is a small ventilation fan and a power port like what you would see on the back of a desktop power supply.

Cool thing about the entire setup it that it could be wired up to control something running on 220, such as an old oven rated at 5000W, assuming you got an adequate SSR.
http://blog.makezine.com/PID_temp_controller.jpg

Taiden
12-03-2010, 01:44 PM
Thanks slopecarver. I'm ordering those components today. I just need to figure out what I'm going to make the larger oven enclosure out of.

Taiden
12-03-2010, 06:02 PM
Ended up winning this today, shipped with thermocouple for $33.00

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rt=nc&nma=true&item=220705511214&si=CYqbyYAF7p1DwVqym1MJQOHJxS0%253D&viewitem=&sspagename=STRK:MEWNX:IT#ht_4826wt_938

slopecarver
12-24-2010, 08:23 AM
I learned a few things about my PID controller that may help you, the relay output just turns on or off the continuity between the posts, I had thought the output was actually a voltage output that I could hook directly to the SSR, but apparently not. I had to wire mine so that it switched the output of a phone power adapter to turn on and off the SSR. If you have any questions about programming it shoot me a PM

I have used mine to cook a top loin steak at 133F for 2.5 hrs and it came out as tender as a fillet and medium rare all the way through, I seared it on the stove top ribbed griddle to caramelize the exterior a bit. Right now it has been cooking a brisket for about 18 hours.
http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs1215.snc4/156718_10100587812640644_9348445_77570579_1009311_ n.jpg

triptester
12-24-2010, 09:46 AM
I use a Ranco ETC 111000 digital control for smokers up to 200 degrees. About $50.00.

Grainger has a digital controller that goes to 300 degrees for $95.00.

http://www.grainger.com/Grainger/CONTROL-PRODUCTS-Temperature-Controller-with-6CJN0?Pid=search

gow589
12-25-2010, 10:42 AM
I am setting up a Kiln for heat treating metal. I just got in the 240v 50a solid state relay. It is pretty much ready to make the metal box to mount everything. It is all done with an OOPIC which is similar to a basic stamp and a type K thermocouple. I programed it to where you input:

Climb (heat up) fast, or slow
Peak temp
How long it holds at the peak temp
Review settings and run
Then monitors cool down and flashes a group of LED's when done


http://www.rc-tech.net/kiln/kiln.jpg