Arduino Reflow Oven Controller Shield

[redwire]

#3569

Hi, I’ve been patiently waiting for the Arduino Reflow controller shield from Rocketscream…http://www.rocketscream.com/shop/reflow-oven-controller-shield-arduino-compatible to be in stock…
Any ideas when this will happen? I’m willing to contribute some design time, for the electronics or pcb…

[rocketscream]

#3920

Hi,

We have a new prototype all ready and tested based on the new MAX31855KASA+ chip with a lot of other improvements.
But, if you look around, you might notice that we had some noise issue on this chip on the osPID Kit.
We are pulling our hair out because it only happens in certain places out there which we are unable to experience on our own.
So, we had to put this on hold at least for now.

[redwire]

#3921

I’ll post about some thermocouple chip issues I know about, I hope this helps.

The older thermocouple chip (MAX6675) had a grounded thermocouple input (T-) and could not read temperatures below 0°C.
The newer thermocouple chip (MAX31855) does not ground the thermocouple (in order to read negative voltages/temperatures) so it is more sensitive to noise. Adding the ferrite beads/10nF cap gets rid of a little RF noise but not other interference.

Your power supply for the OpPid (especially if it’s a SMPS wall-wart) adds noise, so you need to have a ground wire from the OpPid to the metal chassis and earth-ground of your oven/pump etc. But thermocouple junction must not connect to ground (=isolated) and best to run the wires away from high current (i.e. heater/fan/pump) wiring.

You could add an extra filter and cap for the MAX31855 to help with things.

Type-K polarity is yellow (+) (nonmagnetic wire) & red (-) (magnetic wire).

[rocketscream]

#3922

Hi,

I notice that it has to do with the wall adapter especially if it is noisy. It only happens with some of the customers’ unit.
Weirdly, Brett & I couldn’t produce the noise they experience both here in Malaysia and the States.

I think both capacitor & ferrite bead helps to eliminate/reduce the noise couple directly on the wires. But, we had to do something with the incoming power wire from the AC-DC adapter (shield it or move it). I guess that is the noise that magnetically coupled to the thermocouple wires.

Thank you for the suggestions.

[dstorey]

#3923

Since I don’t care about temperatures below ambient (I’m using it for a reflow oven controller), can I connect the T- to ground?

Dominic

[redwire]

#3924

If one thermocouple-leg is grounded, the MAX31855 sets the fault detection (bits). I’m not sure what the osPID software then does- keep the reading, go to a default, halt etc.

[deejay1272]

#3925

@redwire wrote:

Your power supply for the OpPid (especially if it’s a SMPS wall-wart) adds noise, so you need to have a ground wire from the OpPid to the metal chassis and earth-ground

Can we get some clarity on how to ground the osPID? I see a GND pin hole connection inside the box on the input card, but is this what should be used to ground the whole osPID?

Any input from others would be helpful.

Thanks,
Dan

[redwire]

#3926

Dan, here is what I suggest for grounding. For the opPID controller, it would be the same.[attachment=0:3tqi1pzm]Reflow Controller grounding001.PNG[/attachment:3tqi1pzm]

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