How to make Oven for testing - Page 1
Forum section: electronics / testgear

author: jtronix
author_rank: Regular Contributor
timestamp: September 10, 2019, 06:27:27 am
content: Hi,As I have limited budget I'd decided to make my own oven for electronic product testing. Basically I need oven for electronic product operating temperature test.Any recommended guidelines ?

author: bob91343
author_rank: Super Contributor
timestamp: September 10, 2019, 06:46:55 am
content: Perhaps you could be specific regarding size, temperature range, accuracy, and a few other parameters that would help. I too would like a temperature chamber but have never gotten around to building one.My first thought would be a repurposed soft drink cooler with added resistors for heat and a temperature controller of some sort.

author: jtronix
author_rank: Regular Contributor
timestamp: September 10, 2019, 06:51:24 am
content: Temperature range: +35 to +100 deg CAccuracy:- +- 1 deg CSize: at least 200x200 mm

author: Messtechniker
author_rank: Frequent Contributor
timestamp: September 10, 2019, 07:28:23 am
content: Have been thinking about such too.My extra low budget would be based on an old microwave ovenwith the microwave stuff ripped out and replaced with a temperature controllerfor one or several 12 V/21 W (brake) light bulbs strategically placed within the oven.This comes with the advantage of being able to see what is going on inside.

author: Mr. Scram
author_rank: Super Contributor
timestamp: September 10, 2019, 07:59:06 am
content: Quote from: Messtechniker on September 10, 2019, 07:28:23 amWhy start with a microwave oven instead of a regular one?

author: Psi
author_rank: Super Contributor
timestamp: September 10, 2019, 08:30:04 am
content: Maybe some type of peltier mini-fridge that does heating too.

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: September 10, 2019, 12:52:49 pm
content: I solved the same issue a year ago. I bought the cheapest convection oven (grill) which has a timer and heat control. I ripped it apart and replaced the on-off control with a relay which is controlled by Arduino. Two temperature sensors are also installed to monitor and control the temperature. Basically simple on off controller. I could get the temperature controlled from room temp to +125 with about 2deg accuracy.Total cost (< $100)For the cooling part, I bought an old refrigerator for about $60. It works well to cool down to -20C. I ripped it apart and sealed the freezer area to provide better insulation. That makes it faster to reach low temperatures.

author: macboy
author_rank: Super Contributor
timestamp: September 10, 2019, 01:04:52 pm
content: Quote from: Psi on September 10, 2019, 08:30:04 amAny peltier mini-fridge can heat too. If that isn't built in, then just wire up a DPDT switch to reverse the polarity on the peltier (but not the fans). I have done exactly this with a small 8-can cooler. Add a simple PID controller or roll your own from your favorite microcontroller, and you are done.The main issue with this simple design is the range of temperatures. You can't get 100 degC, nor -35 degC. With very good heatsinking on the hot external side of the peltier, you may get a little below freezing (assuming no heat load inside, derate otherwise). For heat, you are mainly limited by the typically plastic and foam construction of the device. The limited range can still be useful. I have tested tempco of multimeters and of voltage references. For this purpose, it is easy to get room temperature +/- 10 or 15 degrees or more.

author: jtronix
author_rank: Regular Contributor
timestamp: September 10, 2019, 01:28:34 pm
content: @EEEnthusiastdid you replace heating element of oven?

author: Psi
author_rank: Super Contributor
timestamp: September 10, 2019, 01:32:56 pm
content: Quote from: macboy on September 10, 2019, 01:04:52 pmIf its not intended for heating the seals and the plastic may not handle 100C very well. So better to get one that can do heating by design

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: September 12, 2019, 07:16:28 am
content: Quote from: jtronix on September 10, 2019, 01:28:34 pmNo I did not. The oven's heating element is excellent for heating boards. I just added a controller in series with the heating element so that I can turn them ON/OFF.

author: GerryR
author_rank: Frequent Contributor
timestamp: September 12, 2019, 11:39:17 am
content: Depending upon the size required, a toaster oven with an added thermocouple and temperature controller will do the job. I converted one for heat treating small parts; of course I am going to higher temperatures than you require. I use ceramic wool as insulation around the unit and added a steel plate to help stabilize the temperature due to its mass / inertia. It also has the added benefit of a built-in timer, all be it for only 60 minutes. Just a thought.

author: jtronix
author_rank: Regular Contributor
timestamp: September 16, 2019, 08:21:55 am
content: Toaster oven is a good choice but I had heard that toaster oven is not suitable for continuous usage for long duration. Would be ok for 3 - 4 hours continuous usage but not suitable for 1 - 2 days continuous use.What about to make our oven custom size oven with Kenthal Nichrome coil wire and PID Temperature controller??I believe this is not difficult to make just needed below components1) Inner surface material: Stainless steel2) Outer body: MS3) Heating coil: I think coil from KENTHAL will fit well4) Temperature Controller with PID logic5) Solid State Relay for on/off coil6) FAN - Fan for uniform heat circulation7) RTD PT100 Sensor

author: Mr. Scram
author_rank: Super Contributor
timestamp: September 16, 2019, 11:09:54 am
content: Quote from: jtronix on September 16, 2019, 08:21:55 amWhat supposedly is the issue with toaster ovens? Building something yourself isn't trivial and is unlikely to yield better results without a lot of trial and error and may not even after doing that.

author: GerryR
author_rank: Frequent Contributor
timestamp: September 16, 2019, 12:05:07 pm
content: Quote from: jtronix on September 16, 2019, 08:21:55 amThere is no problem with continuous usage of a toaster oven; the main issue has been from a safety issue with the outside of the unit getting very hot, but the ceramic wool around the outside alleviates that as a problem. Also, the heating elements are cal-rods (or quartz heaters- mine has quartz) and are very reliable. Also, you will be working at much lower temperatures, so over-heating and over-stressing is not going to be an issue. I've been using mine for several years for heat-treating metals and get to 900 deg. F on many occasions and routinely run it at 600 + deg. F with no issues. Another advantage is the "Toast" mode where top and bottom heaters are on together, making recovery times faster, if the door is opened for some reason. Of course, you can use just the "Broil" or "Bake" modes for slower, less heat requirements. The glass door is nice for process inspection, as well!But, if your just looking for a challenge and want to start from scratch, have at it.

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: September 18, 2019, 05:07:31 am
content: I would recommend to use a grill oven over a toaster. It has larger volument and can take in bigger boards. Provides easy access to keep the boards and comes with built in grill.The one I modified washttps://www.amazon.in/American-Micronic-AMI-OTG-19LDx-19-Litre-Toaster/dp/B07F71R41MVery cheap. About 40$.

author: jtronix
author_rank: Regular Contributor
timestamp: September 23, 2019, 10:09:18 am
content: Thanks EEEnthusiast for sharing link.If it is possible can you please share photo of your oven which you have modified.

author: SilverSolder
author_rank: Super Contributor
timestamp: September 23, 2019, 02:07:42 pm
content: Quote from: GerryR on September 12, 2019, 11:39:17 amWhat sort of temperatures do you use for heat treating?

author: GerryR
author_rank: Frequent Contributor
timestamp: September 24, 2019, 11:33:00 am
content: As I stated above, I use 600+ deg F regularly and have used up to 950 deg F on occasion. Used for tempering.

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: September 27, 2019, 04:09:25 am
content: Quote from: jtronix on September 23, 2019, 10:09:18 amHere you go...My crude oven.I had added a fan on the top of the oven to cool the oven faster. I actually had made an oven to get the reflow profile of lead free soldering. I could achieve that profile to within 5 degC error. The controller was an arduino which controls the relay to turn the Fan and the heater ON/OFF. It had two temperature sensors to sense top side and bottom side temperatures and take an average of the two for the program. I could load a temperature profile using a simple text file over the USB and the oven tracked it to within 5 degC. Heating was well within 2 deg but cooling was a bit off as the fan could not cool it really fast with the vents I had cut on the top.