Convection can make all the difference. The first run failed being undertemp, but notice the parts that didn't reflow were directly above the metal of the tray.
Those boards look absolutely beautiful, aside from the silkscreen, such a letdown. however.... if you dont use silkscreen on your products, 10/10!
I noticed that as well. The parts that didn't reflow were sitting directly over the metal grill. Perhaps for non-convection ovens, it would be good to float/support the board(s) from the corners in some way so that the grill isn't adding any thermal mass to the PCB. Even if the reflow is successful, the grill would definitely create some thermal stress due to uneven heating.. which is what we're trying to avoid, right?
Those boards look absolutely beautiful, aside from the silkscreen, such a letdown. however.... if you dont use silkscreen on your products, 10/10!
Yeah, just the poor silkscreen, bummer.
Yeah that metal grill def caused an issue on the first attempt. Maybe some FR4 or similar as a baseplate to give more even thermals.
Was thinking the E4 would be a great job here but it wouldn't see through the glass, could still get a snapshot on opening the door at the end though.
I have that too, and just like Dave, ended up makign manual adjustments to the profile. After that, I too like ot and consider it reliable.
Yeah that metal grill def caused an issue on the first attempt. Maybe some FR4 or similar as a baseplate to give more even thermals.
I was curious to see what a big piece of copper clad board would do acting as a heat shield and heat sink...
Hi Dave.
I got a Severin sliced bread toaster. Wondering if I can use it for soldering as well.... :-)
As noted, the grill absorbed heat locally. Maybe it would be a better idea to actually use the tray to get a more even thermal distribution. And maybe even tape down the probe to the tray without hooking it on to the PCB. Yeah, the tray will have thermal mass, but that's what the overshoot calibration is there for, right?
I'm also wondering about the temperature offset. You changed it at room temperature because it gave a too high reading and when you logged the temperature, then the oven controller returned a too low reading (compared to the Agilent, 51:30-52:30 ish.) Maybe the probe, or amplifier circuit in the controller, is crusty and doesn't give an accurate reading at room temperature. Maybe the probe offset should be calibrated around a references temperature of 100 or more degrees C?
That temp controller is not very good at all, 7 Degree offset and no decimal points in the reading or offset calibration value. I have previoualy designed thermocouple controllers myself, and you would need to really try hard to mess it up by that much!
Could you please make a follow up video where you trace out the analog part of the controller and check what voltage and temp reference they are using. Are they using the built in 10 or 12 bit ADC? In that case I would expect some white noise generator so that they can oversample and dither the reading.
If anyone is interested, almost every PID controller you buy today, can 'learn' by them selves and any serious company would have a specification of maximum +-.5 degrees in offset (then the thermocouple would be an additional +-1 degree). Also common PID controllers can handle a variety of thermocouples and also PT100/1000 for better acurracy since you rarely reflow your boards at 1300 degrees Celsius.
That temp controller is not very good at all, 7 Degree offset and no decimal points in the reading or offset calibration value.
That's likely just the display output rounding.
Could you please make a follow up video where you trace out the analog part of the controller and check what voltage and temp reference they are using. Are they using the built in 10 or 12 bit ADC? In that case I would expect some white noise generator so that they can oversample and dither the reading.
I already posted the datasheet in the video description.
Most importantly, does it come with a heating profile for pizzas too?
Nice video of the home (small business) reflow owen, especially showing the process and the traps there are (calibration, metal grill etc)..
I wonder though, if you should mentioned a bit more clear that you didn't actually purchase the owen and controller (was gifted), and that the entire set (including materials, delivery etc) would have cost close or over 300 Euros.
A coarse metal grille can cause cold spots - I tend to use a fairly fin mesh sheet which works fairly well.
Another option is to make up some long triangular (think Toblerone) sections of PCB strip (e.g. old tooling bars), about 10mm on a side, by taping 3 strips together with kapton tape, and using these as 'trestles' to seperate the PCB from the shelf. This is also a useful way to do double-sided reflow.
Most importantly, does it come with a heating profile for pizzas too?
For ols school coders.. There's always C1541 .. Disk drive with pizza warming feature pre-installed.
That temp controller is not very good at all, 7 Degree offset and no decimal points in the reading or offset calibration value.
That's likely just the display output rounding.
You are correct since the ADC has 0.25 degrees resolution after reading the datasheet.
After looking carefully on the video, I think they might have made the mistake of not using a proper thermocouple-wire from the connector to the circuit board inside the box. The wires from the connector is soldered to the board, but I have never managed to solder the Nickel based alloy used for Type-K thermocouples, the solder does not wet this alloy. If this is the case, you can just replace that wire and possibly gain several degrees of better accuracy, and you can even leave the box on top of the oven without any problems
I already posted the datasheet in the video description.
I completely missed that, thanks!
But for the same amount of money (123 Euro) you can get much better performance, for example this industrial miniature thermocouple controller (which I have used as an oven controller previously).
http://www.omega.com/pptst/CN7500.html Cost 70 Euro (and then you buy a solid state relay and a fancy box for the remaining 50 Eur you have saved)
This can handle all thermocouples types (even other signals such as 10 mV per Celsius and PT100) from -273 to +1800 Celsius with 0.25% accuracy out of the box without calibration (better with calibration of course). It has dual temperature display and up to 64 different ramp/soak steps with build in extra relays for customizable alarms. Omega also have free software for changing parameters and proper logging/graphing capability for more than 200 devices on the same RS232 or RS485 cable if you ever would like to expand your toaster oven reflow capacity.
Just wondering, whats the go with using SSRs in these things, compared to using TRIACS? Is it primarily just heat dissipation.
Just wondering, whats the go with using SSRs in these things, compared to using TRIACS? Is it primarily just heat dissipation.
A SSR is typically just either a triac or a pair of back-to-back MOSFETS, plus isolation etc. in the same package.
I think some use photovoltaic isolators to drive MOSFETS, which probably reduces losses- a triac drops typically 0.8V, so produces a fair amount of heat when switching heavy loads.
SSRs also have stuff like isolation & approvals taken care of.
BTW I didn't like how it looked like that low-voltage wire could touch the fuseholder.
A SSR is typically just either a triac or a pair of back-to-back MOSFETS, plus isolation etc. in the same package.
I think some use photovoltaic isolators to drive MOSFETS, which probably reduces losses- a triac drops typically 0.8V, so produces a fair amount of heat when switching heavy loads.
SSRs also have stuff like isolation & approvals taken care of.
Is there some other reason to use MOSFETS, I mean at 10A you need a MOSFET with 80 mOhm on-resistance (and 300+ volt capability) which is quite expensive, just to compete with the 0.8 V drop in the triac?
BTW I didn't like how it looked like that low-voltage wire could touch the fuseholder.
And also no varistors or other protection for the SSR, they are usually quite sensitive to voltage spikes and often fail shorted so that the oven would overheat and possibly be a fire hazard depending on what you put into it.
If they'd have used a transformer with a primary center tap and a back panel voltage selector switch, or to save money, just a jumper on the PCB, they could have easily made it 230/115V.
Anyone know of a controller, preferably Arduino-based, that has the only feature of the Beta controller that really interests me, the learning/calibration function?