Kindergarten level question here about short circuit protection - Page 1
Forum section: electronics / beginners

author: DavidHBurgess
author_rank: Newbie
timestamp: May 01, 2019, 02:13:13 pm
content: I'm very new to circuit design, and I'm basically following an "instructable" about how to build a water sensor that will text and email updates. Every thing is very straight forward. (Uses an nodemcu ESP8266 processor and a funduino water sensor, and three wires. 3.3v, GND, and A0.) My issue is that my application may have the water sensor completely submerged (just the sensor, the processor will be high and dry). I imagine if that happens then the wire to the 3.3v and GND will be effectively shorted by the rising water. My guess is that having the 3.3v and GND directly connected would be a bad thing. I'm just not sure what to do about it. I would think dealing with this type of thing if very basic, but it all new to me.Thank you in advance for any assistance you can provide!

author: Manx
author_rank: Contributor
timestamp: May 01, 2019, 02:37:45 pm
content: The problem wouldn't really be shorting anything -- resistance is too big (you can try with ohmmeter leads in a glass of water or your mouth). Problem will be with corrosion (electrochemical effects). So I'd recommend hot snot or some adhesive-lined heat shrink to make the sensor's electronics and connectors waterproof.

author: atmfjstc
author_rank: Regular Contributor
timestamp: May 01, 2019, 02:38:42 pm
content: I don't think there is an "easy" way of fixing this if the sensor is not designed to be fully submerged to begin with. In theory you could seal the top part of the sensor with some substance (see potting, conformal coating) but this isn't trivial for a beginner. Or, you could attach some sort of makeshift float to the sensor such that the top part always stays above the water.

author: Old Printer
author_rank: Frequent Contributor
timestamp: May 01, 2019, 03:35:57 pm
content: I Googled the Fundino sensor and it does not look like it was designed to be completely submerged. Since it is a pretty inexpensive component I would try encapsulating the "top" portion that has the components exposed with something like a good slow dry epoxy. Before that I would cut off the Dupont connectors and direct solder the connections. From the looks of the board I don't think water on the components will damage them, but might affect the readings a bit since it is analog.

author: David Cutcher CEG
author_rank: Contributor
timestamp: May 01, 2019, 06:08:02 pm
content: From the answers so far, I get the impression that you have chosen the wrong circuit for your application.I understand that you might not want to say too much, but . . . we need more info.You are trying to build a sensor. Your Input.Be specific, when it happens.what physically happensdo you want to sense incremental change (continuous), or just a "one shot?"and what type of signal do you want as an output to your system.Wanting to HelpDavid Cutcher "Certified Evil Genius"

author: DavidHBurgess
author_rank: Newbie
timestamp: May 01, 2019, 07:10:58 pm
content: Sorry for not giving more information. Basically I want to put the sensor down in my sump pump well. So long as the power is on, and the pump is working, it shouldn't get wet. If the pump stops working (as it has previously) then I want to trigger an alert. As far as power outages, I plan to send a "heartbeat" single every half hour to an external web application. If more than 30 minutes have elapsed, the an alert will be triggered.Sister's rental property had had flooding issues, I'm just trying to set her up with a basic detector that will text and email when power is out, or water high. Using following "instructable":https://www.instructables.com/id/DIY-ESP8266-WiFi-Water-Sensor-With-Text-and-Email-/All his instructions made sense, but I worried about the sensor being totally submerged. I don't really need to take advantage of the difference levels of sensitivity on the sensor, I just need to know that it is wet, as the entire sensor should be above the level where the sump pump should kick on.Thank you for your reply!

author: ebastler
author_rank: Super Contributor
timestamp: May 01, 2019, 07:26:05 pm
content: I think the easiest solution (if you want to stay close to the instructable) would be to use the Funduino water sensor, but keep it high and dry, away from the actual sump. Instead, solder two wires to the electrodes on the Funduino circuit board, and dip the wire ends into the water you want to detect.It seems that the Funduino sensor has some simple transistor amplifier, and is meant to be quite sensitive to small drops of water, or just humidity in the earth of a potted plant or such. Hence, I think you will not lead the large, multi-strip electrode array on the Funduino circuit board. You can always change the length of the free, non-insulated wire segments which dip into the water if the sensor should be too sensitive, or not sensitive enough.Just give it a try with a glass of water (preferably from the sump, for realistic conductivity) and a pair of test wires soldered to the Funduino.

author: DDunfield
author_rank: Regular Contributor
timestamp: May 01, 2019, 08:28:43 pm
content: Quote from: ebastler on May 01, 2019, 07:26:05 pmLonger wires might pick up stray noise etc. I doubt the amp has a lot of filtering, esp. since it was designed for very short leads, and it will have pretty high gain to detect not-very-contaminated water.If all you want is to know when a sump is filling, just hang a ping-pong ball by a thread from a light microswitch with a lever. Sump dry, ball pulls lever down, activating switch. Sump starts to fill with water, ball floats releasing tension on the thread and switch deactivates. If there's worry about air currents or other factors moving the ball around, put the whole thing in a ABS pipe.Dave

author: DDunfield
author_rank: Regular Contributor
timestamp: May 02, 2019, 01:55:25 pm
content: A friend of mine monitors his sump with an Arduino using an ultra-sonic rangefinder module mounted well above water level. By measuring the water height he can track how fast it's rising/draining .. yeah, he has problems with flooding in the spring.Dave

author: capt bullshot
author_rank: Super Contributor
timestamp: May 02, 2019, 02:08:58 pm
content: This sensor isn't designed to be submerged (other than the gold traces) and certainly will corrode to death if done so.For your application, I'd recommend to get a ready made water level switch of the kind that sometimes is mounted externally to a sump pump.Internally, these are basically a on/off switch, which you can use to trigger the message off your ESP32 board.

author: Old Printer
author_rank: Frequent Contributor
timestamp: May 02, 2019, 07:42:01 pm
content: After foolishly adding a basement to an existing building that wound up a foot below the water table, I became an authority on sump pumps and keeping them running. My location was my printing business and i had some expensive equipment there. Did I mention foolish? I worked through about every conceivable combination. First would be a self starting generator if she can afford it. Second is to add another specialty 12 volt deep cycle battery powered pump set a few inches higher that the main unit. Not cheap, but cheaper than the generator. If the power is out for more than 12 hours she is going to need some sort of backup generator to run the pump, but they can be had for a few hundred dollars for a pull start small one.