Hello everyone.
I am disabled and need to have a walk in shower facility.

The pump unit that I have installed is a 24v unit with a NO flow sensor in the supply pipe. The trouble is that the control unit associated with the system has failed (it fails to turn the pump on) but I know that both the flow sensor works (closes on water flow as tested by meter) and the pump itself is working fine as I have temporarily fitted it up using an old laptop power supply.

A new pump controller to match my system is prohibitively expensive and therefore I want to build a simple control circuit of my own to run the pump using the aforementioned laptop power supply.

What I had in mind was that a DPDT relay is latched on by the flow sensor through the coil when water is flowing This is not a problem. However, I also need some sort of over-run facility to pump out the 'drain-down' water initially and then, after a delay, a further short activation to clear any remaining water in the tray. That is; a two stage over-run.

I do not have any great facility in electronics and so a simple, discrete component circuit board would be necessary. I do have enough savvy though to ensure that all of the main voltage equipment is outside the shower room.

Any help would be very much appreciated.

 

The trouble is that the control unit associated with the system has failed...

Can you fill us in on the details of that unit? Make, model, schematic, whatever you can get. Perhaps it can be easily fixed. I assume that would be OK?

You say the pump runs off the ~19V DC provided by a laptop power supply? So it's a 24V DC pump? Do you know the current rating?

 

Hi, thanks for replying so quick.

The controller is labelled 'Phlexiflow' and the output is indeed 24v at 2.5A with a 50/50 usage cycle. Unfortunately, I have no schematic and the controller is a sealed unit with everything fixed inside using a bituminous potting compound. The exterior panel has 3 small variable resistors labelled pumping cycle, end of shower over run and pump speed respectively. I believe the laptop power supply to be about 90W. With the 19v laptop supply voltage, the pump seems to be working quite happily at the required speed though I suspect that I shall have to be fairly cautious with the duty cycle even though it is well ventilated.

 

This type of thing will do the job (24VDC versions are available), and potentially better than the original controller...

http://www.ebay.co.uk/itm/Genie-NX-...ial_Automation_Control_ET&hash=item19e782dd5d

 

Thanks for the info. Unfortunately, it is rather more than I wished to pay. I was hoping more for a simple 556 timer circuit which will do the job.

 

Thanks for the info. Unfortunately, it is rather more than I wished to pay. I was hoping more for a simple 556 timer circuit which will do the job.

I think the cost of such programmable controllers is something of a bargain considering that there is virtually no more hardware to add.

When you factor in that, for a custom unit, someone has to spend time designing it, then it needs to be built and tested, there will probably be some time spent tweaking and troubleshooting then the whole thing needs to be boxed up with appropriate connectors to make it into a safe and reliable product plus the cost of the parts (which is always much greater than first thought) a fully custom diy solution does not offer any great savings; and actually, if you factor in all the hours spent, is many times costlier. And while you're spending time designing and building the thing, you're still without a properly working shower.

 

The exterior panel has 3 small variable resistors labelled pumping cycle, end of shower over run and pump speed respectively.

What control ranges do these provide?

 

I think the cost of such programmable controllers is something of a bargain considering that there is virtually no more hardware to add.

When you factor in that, for a custom unit, someone has to spend time designing it, then it needs to be built and tested, there will probably be some time spent tweaking and troubleshooting then the whole thing needs to be boxed up with appropriate connectors to make it into a safe and reliable product plus the cost of the parts (which is always much greater than first thought) a fully custom diy solution does not offer any great savings; and actually, if you factor in all the hours spent, is many times costlier. And while you're spending time designing and building the thing, you're still without a properly working shower.

I am sure that it is a wonderful machine but as I said before, the cost for it is too high for my budget. I am looking for a simple solution built on vero board or similar along the lines of a simple timer circuit to cause the pump to run on for approximately 40 seconds after the water flow stops (that is the flow sensor switch goes open circuit) then stop the pump. Ideally, I would like the first timer to initiate a second timer to run the pump for around 30 seconds around 45-60 seconds later.

 

What control ranges do these provide?

The timer periods are similar to the figures that I have given to blocco in the previous answer. The only one that I do not need is the pump speed control as the voltage used appears to already run the pump at the correct speed.

 

An Arduino Uno is only about $6... cheap, easiest solution

 

An Arduino Uno is only about $6... cheap, easiest solution

Thank you. I had already considered using an Arduino but as I posted in my original posting, I have absolutely no knowledge of how to use such a device. My sole experience is to lash up discrete components onto a patch board to get them working and then to transfer the discrete components onto a project board for soldering. I am having to use the shower at the moment by connecting the pump to the laptop supply directly using a low voltage flexible cable across the shower room floor and manually starting and stopping the pump.

Ideally, what I had in mind was that the flow switch charges up a simple capacitor/resistor timer (timer 1) as well as operating the relay coil, which activates the timer after around 30 seconds for a short interval to again activate the relay coil and restart the pump. Then, the activation of Timer 1 charges up a second timer (Timer 2) to repeat the process then shut down. I should imagine that an op-amp would be required in each timer to facilitate charging time threshold but I am only guessing.

I am sorry if this explanation is not very clear.

 

You need 3 timers: 1) for the initial over-run, 2) the delay before the drain-down run, 3) for the drain-down run. The timers must also be re-triggerable i.e. if the controller receives an input from the pressure switch within this cycle; the cycle must start again from the beginning.

 

cause the pump to run on for approximately 40 seconds after the water flow stops (that is the flow sensor switch goes open circuit) then stop the pump. Ideally, I would like the first timer to initiate a second timer to run the pump for around 30 seconds around 45-60 seconds later.

If I've understood you correctly won't you need 3 timers?
T1 , 40 sec, started when flow switch goes off;
T2, 45-60 sec, started when T1 ends;
T3, 30 sec, started when T2 ends.

 

Both of you are quite correct, it will need 3 timing sequences and as blocco says, probably needs a reset.

 

Can either of you comment upon whether these boards can be utilised for the sequences that I need? www.ebay.co.uk/itm/400788130469?var=670339068947

 

The Ebay link doesn't give enough detail of the cycle timing to know if those relay boards will suffice.

If you want a DIY solution it could be based on this:

 

At Alec T. I have taken a chance and ordered a couple of the boards, at the price I can afford to do a little experimenting and the descriptions sound promising.


However, I am continuing to explore the use of discrete components. I have come across this circuit using Livewire which is a flip-flop with holding facility. However, can anyone suggest a way of replacing the (lower) output LED with an opto-isolator to enable me to use a relay? Even though I get around 13V at pin 3 of the 555, all attempts that I have made with the Livewire programme results in too low a voltage (less than 1V) to operate a relay coil.

 

In that circuit I question the use of R5/VR2/R4 to reduce the supply voltage to IC1, since the current drawn by the IC1 load will affect that supply voltage significantly (as you have found). Better to use a LM7812 or LM317 to provide a regulated supply?
Do you really need an optoisolator? The 555 can switch a relay directly.

 

@alec T.
I only included the voltage divider to bring the circuit within the 18V maximum for the IC as the power supply is 19V but in the redrawn circuit, a series resistor (68 Ohm) appears to drop the overall voltage to just under 17.5V (11.42V under load). I removed the current limiting resistor and D2 and replaced it with a 12V relay. The relay appears to operate OK with the indicated 11.42V in the animation.

Incidentally, would the flow switch (NO) replace SW1 in the circuit in some way as this circuit only requires a momentary contact and the flow switch would be closed for some time whilst the shower is running. I was hoping that some sort of Schmidt trigger layout would give me the necessary pulse when the flow switch opened as in the circuit animation, the circuit resets once SW1 is open and C1 is fully charged. Failing that, if I ran the pump initially with the simple relay connection shown in the second circuit, could the second set of relay contacts (NO) be used to provide a momentary pulse to the first circuit as it closes? If I used a DPDT relay in the first circuit, could it be possible to do the same thing to provide a second pump using a second circuit 1?

I apologise for my lack of knowledge on the subject and hope that you can bear with me.

 

If the flow switch is a volts-free type it could be used to generate a trigger pulse when it opens. Like this:

According to TI's datasheet for the 555, " Operation is specified for supplies of 5 V to 15 V". I wouldn't be happy running the 555 above 15V. Can you be sure your laptop supply is never > 19V, e.g. at power-up?