We have a filter outlet nex to the sink that keeps getting left on. People start filling a jug and get distracted and walk away. The old filter (that died) beeped when water flowed through it.I want to make somthing to duplicate that. I was planning on using a old phone charger as a power supply. I found a coffee maker flow meter on amazon for $5. not sure if any voltage comes out when it's not turning tho. And I was going to use a old motherboard speaker, but not sure how to make it beep. Thought about using a continuous beeper, but that sounds like it would make constant noise like my home made continuity testet. how do I make it beep. Do I need a 555 timer or is there an easier way? Can I use the mob speaker or do I need a buzzer? Will the flow meter work as intended, or will it put out constant voltage that goes up with flow, and can that be corrected with a resistor? This is the sensor. http://www.amazon.com/gp/aw/d/B00LZJXY3U/ref=mp_s_a_1_1?qid=1437768292&sr=1-1&pi=AC_SX110_SY165_QL70

 

I believe that sensor will put out a series of pulses. You would normally count them over a set period to get flow rate. You might be able to use the presence of any pulses at all as your trigger.

Using a buzzer would free you from having to build an oscillator for your speaker. Then you could use a 555 to pulse the buzzer.

Water and electricity don't mix. Be careful.

 

Sounds like a fun little project. Yes that sensor will work for you. You can power it with anything from 5 to 18 VDC, so cell charger will work if it is 5 V, 6 V, 9 V, 12 V. Given that the sensor makes pulses when water is flowing (the faster the water, the faster the pulse rate), the low rent approach is to get a continuous Piezo beeper, connect the + beeper lead to your + V, and connect the - beeper lead to the sensor output. When water runs the sensor will pull the beeper - lead to GND with each pulse, so you should get a chirping or trilling sound.

ak

 

thanks for the input guys i will let you know how it works.

 

Self closing faucets are made for this exact problem. If a person walks away the water shuts off. I looked around on Google and found several examples priced between 50 and 80 dollars. No circuits, no batteries, no speakers, no worries.

 

those dont replace this a filter fauscet, and running back to turn it on every minute while it fills a jug would just as bad.

so it kindof works. spent less than 5 dollars , and it chirps rapidly while water is flowing... however when the water stops it may stop with the circuit open or it may stop with circuit closed and constantly screech. the rotor has a little magnet in it, and the pcb just has a diode and a magnetic switch with 3 leads. so as the rotor turns, the polarity of the magnet switches it off and on. i played with tapeing a magnet to the side so it always stops in the off position, which works fine when your blowing through it, but not reliably with water.

maybe the timer with a on/off flow switch would work better... if i find one.

the chirp of the pizo beeper is higher pitched than i would like, how do i find one with a lower more satisfying beep? would a non continuous peeper solve the problem with it stopping on closed?

 

This is a classic problem when monitoring a fan to see if it has died - it can stop with the tach signal either high or low. The solution is to AC-couple the signal so that when it stops, a resistor on the output side biases the signal to whichever state you want. In the case of a fan, you want an alarm when the signal stops pulsing. In your case, you want no alarm when it stops.

Depending on the output stage of the Hall effect sensor, this *might* work: Insert an electrolytic capacitor between the beeper - lead and the sensor output with the capacitor + end toward the beeper. This puts the capacitor in series with the beeper and the sensor. Connect a small rectifier diode (1N4002, 4003, etc.) *across* the beeper. Anode goes to Vcc, cathode goes the junction of the beeper - lead and the sensor output.

How big is the capacitor? Depends - how big is the beeper? Or, make/part number? If you know the typical current draw of the beeper, it is a simple calculation. If you don't, but you have a few capacitors, try them and see if one is big enough. Start with 470 uF if you have one. The capacitor discharges into the diode when the sensor output is high, and charges through the beeper when the sensor output is low. To calculate a capacitor value, here is the first-order approximation method:

ec = it > change in capacitor voltage (e) times the capacitor size in farads (c) equals the current (beeper current) (i) times the time the current is flowing (the minimum pulse time) (t). Rearranging:
c = (it)/e

For the cap to charge up 5 V with 10 mA of beeper current in 1/10th second (all guesswork here), that works out to 200 uF. A larger cap gives a louder beep at low water flow rates.

I tried to find the sensor user manual online but couldn't. If this doesn't work, it's probably because the Hall sensor output is open collector. That will take a bit more of a circuit, but still not very complex.

ak

 

I'm still puzzled by the whole situation you believe this beeper will "fix".
WHY do these "people" not have enough sense, or would it be consideration, to shut off the water when they finish the task?
Who exactly will respond to the beeper? Is it there so YOU can notice that the water faucet is still on and can repeatedly correct a problem created by the laziness of other people?
I am kinda bitching about the situation, but I am also quite curious as to the root cause which inspired the need for such a warning.

 

well basically you start filling a jug, simple enough ya. than in the 10-20 minutes it takes the low gravity fed pressure to fill the jug, life happens. you get a phone call, or get distracted by the tv, or the dog wants out, or maybe as soon as the water starts filling you need to go pee. its easy to get distracted and than you may have a mess, and hopefully there is still enough water to shower with. the old water filter used cartridges that where $150-200, they supposedly last over a year, but after a few months the water slows to a trickle. that system would beep a slow loud beep whenever water flowed through it, you could hear it throughout the house. the new system is way cheaper, and if i get a solution i may try to make a uv filter as well.

i was playing around with some capacitors hoping that would only fire when the circuit switched, but it pretty much just changed the tone. i never thought to put a diode between the beeper contacts tho. the sensor it self is a hall effect sensor and a diode, setup similar to this

i thought about using one of thees. it seems to be an anti siphon valve with a magnetic diagram and a hall effect sensor. i might be able to make one, seeing as i have a hall sensor and some small neodymium magnets. does neodymium rust or corrode?

 

What is the power source for the circuit and the beeper? At 5V the beeper won't be very loud, but if it is loud enough that simplifies things. Also, can your skill level handle a IC and some Rs and Cs on perf board or a similar prototyping technique?

ak