Temperature issues related to use in Dishwasher

[Clayton Karmel]

We have a device which needs to survive dishwasher conditions. We believe most dishwashers operate up to 71C, but may reach 82C during 'sanitation' phase/drying.

This is very close to the nRF51822 max operating temperature of 75C. Our intention is to suppress operation of the radio and peripherals (except counter and temp sensor) above 55 or 60C, monitoring the internal die temperature until the temperature has eased. We would use the internal R/C oscillator rather than xtal oscillator(s).

We are not using the internal 1.8V regulator, but are supplying 1.8V from an external source.

Could you confirm that this light operation of the nRF51822 at temperatures well below the maximum storage and barely above the max operating temperature should not be a problem?

[Roger Clark]

Is your device actually inside the wet area of the dishwasher?

The rest of the dish washer doesn't get that hot, and the control board is usually well away from the heated internal wet box of the machine.

And, aren't dishwashers normally sealed metal boxes, in which case the RF signal is unlikely to be detectable outside the the machine.

Even if you put the nRF52 outside the sealed wet area, most machines have metal front's and sides which is going to considerably shield the RF unless you perhaps site the nRF52 in the control panel on the front of the machine, which is often made of plastic

[Hung Bui]

Hi Clayton,

We extended the temperature range to -40 to +85C degree. However the low voltage setup is not valid if you want to achieve this range, LDO or DCDC needed. Please have a look here.

You should also consider to use the chip with Extended Industrial Temperature Range, which support from -40 to +105oC which is explained here.

You should not operate the device outside of the spec as it will result in unexpected behavior.