53 votes

Moisture Trapped in IP66 Enclosure

Here's what happened to a product I designed that was IP69K (Protection against powerful high temperature water jets). It was installed in China and failed after about a couple of years. When looked ...
  • 396k
49 votes
Accepted

Why are SMD LEDs shipped in a sealed bag containing desiccant?

Through-hole components are generally hand or wave soldered. These apply on local heating to the pads and not to the component itself. SMD parts on the other hand are generally reflow soldered. This ...
22 votes

Moisture Trapped in IP66 Enclosure

Andy exactly describes the mechanism I have also seen . Because of this I favor inverted bucket case designs which do not rely on seals, wherever possible. "The definition of waterproof is the hole in ...
  • 5,108
20 votes

Moisture Trapped in IP66 Enclosure

I once found water in a box like that installed INSIDE a house. I was baffled about where it could come from. Turns out the water wicked itself through the wire going into the box, coming from another ...
  • 1,220
17 votes

Why are SMD LEDs shipped in a sealed bag containing desiccant?

The LED package will absorb moisture. When you raise the package to soldering temperature, the moisture turns to steam and the increased internal pressure will damage or destroy the component. We ...
  • 22.9k
13 votes
Accepted

Storing Electronic Components Outside

This is answered in the datasheets of the individual components. Look up the storage temperature spec. Most components don't contain anything liquid that cares whether it's below 0 °C or not. ...
9 votes
Accepted

Moisture Sensitivity Level - More than one chip in sealed bag

Open the bag, take one IC out, place a teaspoon or two of white rice into the bag, and make sure to reseal airtight. The rice will take up most of the mosture that you've introduced with the ...
  • 633
8 votes
Accepted

How do you measure soil moisture using a capacitive sensor?

It's called capacitive because the two copper planes in your sensor are the two plates of a capacitor. In a physics textbook these two plates might be drawn facing one another, with empty space in ...
7 votes

Storing Electronic Components Outside

Many components have a storage temperature range of -40C (some are -65C) to between 100C to 160C. The specifics of your components would need to be checked. More to the point is humidity, as the ...
  • 21.5k
7 votes

Storing Electronic Components Outside

Humidity (low is better) is more important than temperature. If the leads get corroded the solderability suffers and they may no longer be easily or reliably useful. Maybe you could put them in air-...
7 votes
Accepted

Capacitive moisture sensor not quite working

You're using a bipolar 555 and the original obviously has a CMOS TLC555 (marked TL555). There are a number of differences aside from power supply current draw including greater output swing (...
6 votes
Accepted

Use of desiccant for storage and delivery of electronics

There are actually a lot of variables that go into figuring out how to properly package, ship, and store electronic devices. The Joint Electron Device Engineering Council (JEDEC) maintains a standard ...
6 votes
Accepted

How does moisture get into silicon chips?

Silicon is not the problem, the problem is with the plastic packages. Plastic is slightly porous. If the absorbed water turns to steam during reflow soldering, bad things happen.
  • 11.2k
6 votes

How does moisture get into silicon chips?

The plastic package moulded onto the chip and leads is permeable to water. This water is not usually a problem to the IC itself. However, when the package is heated to solder it onto the board, it can ...
  • 145k
5 votes
Accepted

Wire Wrap Joint in High Humidity

Properly made wire wrap joints are probably the most durable of electrical connections. I worked in the defense industry for many years during which most of the connections between circuit boards ...
  • 15.2k
5 votes

Moisture Sensitivity Level - More than one chip in sealed bag

My understanding is that IC's are moisture controlled because excessive moisture can do bad things during reflow, causing the chip to explode or just move prior to soldering being finished. If you ...
5 votes
Accepted

Are oil-filled transformers ever run at a vacuum?

Large oil-filled transformers use the oil as a thermal transfer medium as well as a dielectric. That's why the cooling fins are on the outside. If there was a vacuum inside the coils would run very ...
5 votes

Moisture Trapped in IP66 Enclosure

I've observed, learned from (the hard way), and later protected from this phenomenon on a number of outdoor products. You can also see a similar effect if the enclosure becomes very hot (e.g. direct ...
4 votes
Accepted

How to calibrate HR202 humidity sensor?

As WhatRoughBeast already mentioned the data sheet is readily available by simply goolgling "HR202 Humidity". Here is the link. The accuracy and resolution are clearly stated. Note that the sensor ...
  • 498
4 votes

Raspberry Pi in mineral oil enclosure

Just buy a can of conformal coating spray and put it on the board. That will protect everything but the connector pins from humidity. https://www.aitechnology.com/products/conformal-coatings/...
  • 10.4k
4 votes

How to use gold finishing to reduce corrosion on a moisture sensor?

Many of the “hobbyist” soil probe circuit designs actually pass DC current through the probe, which inevitably results in electrolytic corrosion regardless of the metals used. If you only briefly ...
4 votes
Accepted

Why does my Vbe multiplier voltage oscillate when wet?

Good experiment with detailed measurements! We have no evidence that it's oscillating (in the sense of an L-C or R-C oscillator) though an oscilloscope may reveal something a DMM can't. It was clearly ...
  • 66.1k
4 votes

AHT10 temperature and humidity sensor does not work anymore

Issue is in the Level shifter. Manufacture somehow replaced a wrong chip K27 aka MMT2227 instead of 72K aka 2N7002 dual N-MOSFET. I've checked few 2N7002 dual N-MOSFET marking codes just to confirm ...
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4 votes
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Heating elements on humidity sensors like SHT32 or HTU21D, what are they for?

There may well be some hints in the documentation, for example: The heater is intended to be used for functionality diagnosis: relative humidity drops upon rising temperature. The heater consumes ...
3 votes
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How to read out data from this moisture sensor?

From the schematic, the LM393 is acting as a comparator. It compares the voltage from VR1 (which can be considered the reference voltage) to the output of the voltage divider formed by the 510K ...
  • 15.2k
3 votes
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How "pinless" moisture meters work?

As it happens the SignalPathBlog recently looked at a different moisture detector. That one uses a capacitive sensor (just a plate of metal) and detects when it is near a conductive object which could ...
  • 79.1k
3 votes

Is there a sensor that is equivalent to a dry toothpick?

The best approach for determining when baked goods are done is to put a thermocouple probe in the item being baked. The basic idea is bake until the probe reports that the item has reached its ...
  • 26.5k
3 votes
Accepted

Measuring humidity with Honeywell 5030/5031 sensors

The resistor is between the output and 0V of the supply. Minimum load implies it requires to be connected to a load to maintain a stable output, essentially it is there to prevent oscillation and ...
  • 512
3 votes

Waterproof Fan Failing In A Chamber With 100% Relative Humidity

I think the old adage of you get what you pay for applies here. Select a professional quality fan with IP67 or IP68 ratings made for the application. A Sanyo Denki (link) waterproof fan would seem to ...
  • 5,461

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