Was hoping I could get some help building a simple water switch to power a small motor using a AAA battery as a power source.
I’ve bought an arduino test board along with a resistor kit (1ohm-1Mohms) and a kit of various transistors. I’m trying to wire up a simple switch with 2 probes that power the motor when in contact with water.
I’ve researched the very basics of reading schematics and tried a few designs I could find on the internet but none have worked out so far. It seems like this should be fairly simple to wire up but I’m fairly lost figuring out which transistors and resistors will be needed for a AAA power source (if that will even work).
Here are some of the switch designs I’ve tested so far with slight variations:
A one-time poster who uses the word simple three times in what they are doing and does not know the answer they seek always makes me nervous they will vanish without sharing the success they had.
There are as many fun ways to do what you want, as there are active members here.
What logic is the Arduino going to perform?
Why one AAA cell and not two for 3 volts?
What is the motor doing besides spinning? (vibration)
The circuit may drop over .6 volts in operation so what type of motor are you using that can run on less than one volt and do anything?
I have interest in your project because at my age we start to get some leakage down below if you know what I mean. :oops:
A one-time poster who uses the word simple three times in what they are doing and does not know the answer they seek always makes me nervous they will vanish without sharing the success they had.
There are as many fun ways to do what you want, as there are active members here.
What logic is the Arduino going to perform?
Why one AAA cell and not two for 3 volts?
What is the motor doing besides spinning? (vibration)
The circuit may drop over .6 volts in operation so what type of motor are you using that can run on less than one volt and do anything?
I have interest in your project because at my age we start to get some leakage down below if you know what I mean. :oops:
Christopher
Hi Christopher,
Thanks for responding. I understand your hestitation about 1 posters (I’m a web developer and have answered a handful of questions on Stack Overflow, never to hear from them again).
Currently I’d just like to get the switch working but eventually would like to program some surging behavior.
I’m playing with some top water and submersible designs and the form factor I have in mind fits one AAA, not to say that I can’t tweak things to use 2 of them if needed.
The motor will be running a propeller for propulsion (doesn’t have to be particularly fast).
I actually have a few different motors to test with. The first I tried was a small cell phone vibration motor (I think) but without the weight for vibration. Another one is the motor that came with the arduino kit. A third motor is being shipped from Amazon currently, believe it’s a 1.5V 19k RPM high torque motor (can get more specs if needed). The cell phone motor was also a 1.5V motor. As long as it’s not too large I’m pretty open on what kind of motor to use, I’ll know better what I need once things are working and I can actually test it out.
I’m just using the arduino kit currently to prototype the circuit design with the bread board and not really using the programming functions.
One 1.5V battery will not power the Arduino, don’t know about your motor since you haven’t given any details…
You need between 7 and 12V to power the Arduino when you’re using the DC connector…
Hmm probably should have left out mentioning the Arduino, I’m currently just using the attached bread board for circuit design. The device itself will be too small to have the Arduino attached to it.
I ordered a motor from amazon that stated it was 1.5V (it does run off the AAA when connected) and had a size that I was looking for. If I need to order a new motor that’s not a problem, my issue is that I’m not sure how to make sure all my parts match each other (motor, power source, transistors, resistors etc.).
Your second link is the right start for driving the motor. But depending on the motor you may need a bigger supply (i.e. battery or batteries).
That one did seem the most promising since it was both 1.5V and powered a buzzer rather than an LED.
I spent about 3 hours trying to get it to work but each time got no power to the motor even when directly touching the water probe leads together. The AAA battery I’m using does power the motor, is it possible it wouldn’t after adding the transistors and resistors to the equation? I was hoping the switch would just close the loop and power the motor when water was detected, not change the power from the battery to motor.
When pinning out the design, it’s my understanding that the PN2222 and PN2907 have the location of their emitters (which are negative and always on the side with the arrow in the schematics?) reversed, right? I actually tried all possible orientations anyway with no success but would be nice to know I’m reading the designs correctly.
The “problem” with all of the circuits you’ve linked to isn’t so much the circuits but the nature of water. Salt water is a good conductor. Pure water is a good insulator. Real water can be anywhere in-between. The circuits linked to try to use the conductivity of the “water” to detect it’s presence.
Perhaps you could tell us more about the exact nature of the watery conditions to be detected. There’s more than 1 way to detect water.
Mind you it, whatever it is, should work better than my “auto” windshield wiper speed control does.
amenconi:
I spent about 3 hours trying to get it to work but each time got no power to the motor even when directly touching the water probe leads together. The AAA battery I’m using does power the motor, is it possible it wouldn’t after adding the transistors and resistors to the equation? I was hoping the switch would just close the loop and power the motor when water was detected, not change the power from the battery to motor.
That would seem the more prudent approach (to me anyways). You need to turn the motor on (by touching the wires together - i.e. closing the circuit), so get that working on first and then work the water part (i.e. how to sense it). The circuit looks fine, if you were staving the pnp transistor (Q2) a bit you could always lower R3 (say, to 1k or even 500). As for the transistors, make sure you get the legs/pinout correct. The following two links should give you the proper pinout.
I drew the basic circuit because I could not find it on the web. You will lose .6 volts across the transistor is why I say use 3 volts but go ahead and try a single cell. Water needs minerals in it (salt) to conduct so distilled water will not work.
Mee_n_Mac:
The “problem” with all of the circuits you’ve linked to isn’t so much the circuits but the nature of water. Salt water is a good conductor. Pure water is a good insulator. Real water can be anywhere in-between. The circuits linked to try to use the conductivity of the “water” to detect it’s presence.
Perhaps you could tell us more about the exact nature of the watery conditions to be detected. There’s more than 1 way to detect water.
Mind you it, whatever it is, should work better than my “auto” windshield wiper speed control does.
That is a good point. In my test setup I start by first touching the probes together since I assume if that doesn't power the circuit then no type of water will either. I then have a bowl of tap water and container of salt. I figured after getting a design that at least worked with touching the probes I'd test with the bowl of water continually adding salt until the motor powers on. At that point if I need to switch to be more sensitive with "cleaner" water at least I have a working design that I can tweak and iterate on.
amenconi:
I spent about 3 hours trying to get it to work but each time got no power to the motor even when directly touching the water probe leads together. The AAA battery I’m using does power the motor, is it possible it wouldn’t after adding the transistors and resistors to the equation? I was hoping the switch would just close the loop and power the motor when water was detected, not change the power from the battery to motor.
That would seem the more prudent approach (to me anyways). You need to turn the motor on (by touching the wires together - i.e. closing the circuit), so get that working on first and then work the water part (i.e. how to sense it). The circuit looks fine, if you were staving the pnp transistor (Q2) a bit you could always lower R3 (say, to 1k or even 500). As for the transistors, make sure you get the legs/pinout correct. The following two links should give you the proper pinout.
Also, just to verify, in a diagram the side of transistor with and arrow is always the emitter, and for PNP transistors the emitter is positive and the NPN transistor’s emitter is negative?
I drew the basic circuit because I could not find it on the web. You will lose .6 volts across the transistor is why I say use 3 volts but go ahead and try a single cell. Water needs minerals in it (salt) to conduct so distilled water will not work.
The motor needs to draw less than 100 ma.
Any additions or corrections are welcomed.
Christopher
Looks great. I know I have the transistor and resistor, let me check and see if I have diode. Once I have that I'll test with both one and two AAA batteries.
Edit: Looks like the arduino kit came with 1N4148 diodes which according to Google should function the same as the one you have in your design.
The original circuit has a sensitivity or gain of 100. Adding the extra transistor known as the Darlington combo will push the sensitivity to well over 10,000. (100 x 100) Now you need to use 3 volts as about 1.5 volts are lost to the circuit and battery decay.
The original circuit has a sensitivity or gain of 100. Adding the extra transistor known as the Darlington combo will push the sensitivity to well over 10,000. (100 x 100) Now you need to use 3 volts as about 1.5 volts are lost to the circuit and battery decay.
Christopher
This is great. I'm gonna do some testing with the original design and see if it's sensitive enough but very nice to have a back-up plan.
For some reason though the latest design image link is broken. Though I don’t suppose chaining the same transistor twice will be that complicated.
Thanks for all the help. I’ll update thread if my project goes anywhere and actually yields something demonstrable.
I finally received my 3V batteries and tested the version of the circuit with the darlington chain for increased sensitivity and it worked great. Before I had to dump a bunch of salt for the emerged probes to complete the circuit but the new design it worked right away with regular tap water.
[http://www.oldtemecula.com/sparkfun/water-switch2.gif](upload://kORE9O1QMipnsXS5XR4oix8xLXl.gif)
