12v Water pump for child's kitchen -Is it safe? How do I power it/can I convert to lower voltage?

Thread Starter

TogetherInElectricDreams

Joined Jan 23, 2019
48
Hello everyone,

Sorry if these are silly questions but I am not electronically minded, although I have picked up quite a bit since joining here. Please could I get some advice? I am making a working tap feature for my son's play kitchen. I've seen a good idea here using a campervan tap and a 12V water pump -this gives a more realistic working tap.

Is this a safe idea? If so, how can I power it safely?
If not can I convert the 12v to 5v so it can be used on a USB port?
If it is unsafe and I am unable to convert, would a 5v pump work and would I be able to wire it in the same way (to a power source, then the tap -ultimately I just want the water to flow like a "real" tap).

If you have any other suggestions I would be most grateful for your advice.

Please explain like I'm 5! I am here to learn and look forward to hearing from you. Thank you in advance.
 

MaxHeadRoom

Joined Jul 18, 2013
19,466
Is it possible to set up a small holding tank, such as a plastic container of suitable volume?
This would be just a simple gravity system and would not require any electrics.
Presumably the reservoir would still be required for a pump system.
Also a pressure sw or other sensor would be needed for shut auto off when tap is off.
If you can set the head height as high as possible to give some suitable pressure.

Max.
 

djsfantasi

Joined Apr 11, 2010
5,849
You could likely convert the pump, but it would be much easier to get one of two things.

A 5 volt pump, but you need to know how much current it uses. USB ports can only supply a limited amount of current. 1A at most but some can only supply 0.5A

Another approach is to look on Amazon for a 12VDC power pack. I’d look for one that looks like a laptop power adapter. You can also get a matching jack.
 

Thread Starter

TogetherInElectricDreams

Joined Jan 23, 2019
48
Is it possible to set up a small holding tank, such as a plastic container of suitable volume?
This would be just a simple gravity system and would not require any electrics.
Presumably the reservoir would still be required for a pump system.
If you can set the head height as high as possible to give some suitable pressure.
Max.
Hi Max,

Thanks for your reply

If you mean like a hand pump, then yes I've looked into them but I actually think they'd be more work as I'd lose space under the sink that is meant for a dishwasher. I've seen another electric pump system (here) but the guy isolated with a switch which I found a bit of a shame and takes away from the play experience IMO. I had thought of doing it with a dimmer switch but I'd really like to do it with the camping taps I've seen! It'll look ace and be fun. I'd still do as you've said and have a tank at the back and the water will just flow round :)
 

MaxHeadRoom

Joined Jul 18, 2013
19,466
No pump involved, I meant providing a head of water from a tank higher than the sink, as often used in some remote homes as in roof reservoir for a water supply that has a hand pump well.
The spigots I referenced have a simple tab type operator that self closes when released so no accidental left on possible.
Max.
 

Thread Starter

TogetherInElectricDreams

Joined Jan 23, 2019
48
You could likely convert the pump, but it would be much easier to get one of two things.

A 5 volt pump, but you need to know how much current it uses. USB ports can only supply a limited amount of current. 1A at most but some can only supply 0.5A

Another approach is to look on Amazon for a 12VDC power pack. I’d look for one that looks like a laptop power adapter. You can also get a matching jack.
Hello again D J Fantasi!
Thank you again for your help. Your suggestion sounds great. If I were to get the 5V pump it would be this https://www.aliexpress.com/item/32810082354.html current -is that watts? If so it's 3W so I don't know what that means USB wise other than, it's more.

Being cheeky but I actually have another question about powering the whole kitchen, if you have time -you always give such helpful answers that's why I'm asking. :-D It might also help me answer this question.

Thanks a mill
 

Thread Starter

TogetherInElectricDreams

Joined Jan 23, 2019
48
No pump involved, I meant providing a head of water from a tank higher than the sink, as often used in some remote homes as in roof reservoir for a water supply that has a hand pump well.
The spigots I referenced have a simple tab type operator that self closes when released so no accidental left on possible.
Max.
Hi Max, no that wouldn't work due to the design of the kitchen, nowhere to put it and I'd like it to look "tidy" so all the gubbins round the back or packed away but thanks for your suggestion :)
 

MaxHeadRoom

Joined Jul 18, 2013
19,466
You could use any 12vdc wall wart type supply, I see from the video the tap is apparently always-open style and water only flows when the N.O. switch or push button operated.
Max.
 

djsfantasi

Joined Apr 11, 2010
5,849
Hello again D J Fantasi!
Thank you again for your help. Your suggestion sounds great. If I were to get the 5V pump it would be this https://www.aliexpress.com/item/32810082354.html current -is that watts? If so it's 3W so I don't know what that means USB wise other than, it's more.

Being cheeky but I actually have another question about powering the whole kitchen, if you have time -you always give such helpful answers that's why I'm asking. :-D It might also help me answer this question.

Thanks a mill

A little education. First, Ohms Law states that...
Volts = Amps * Resistance​
Similarly calculating Watts (W) has a similar equation...
Watts = Volts * Amps​
You know the pumps voltage (5) and it’s watts (3) so with a little rearranging, we can calculate the amps required...
Watts = Volts * Amps
Amps = Watts / Volts
Amps = 3 / 5
Amps = 0.6A​
That’s a little over the possible 1/2A limit, but under 1A. If your using a USB charger, I don’t think you’ll have a problem.

As far as the tap, I don’t think a dimmer will work. I suspect something like a PWM motor driver would be needed. But it doesn’t look like that pump is meant to be adjusted. Look into a rotary switch. There are two types. A lamp switch likely will only turn in one direction. Which is ok if that’s the desired action. I’ve provided a link to one example.

Then there are rotary switches that can be turned in both direction. A stacked deck rotary is an example of this. While it may have multiple contacts, you can wire them together for better action. I’ve provided a link to one example. This one has four contacts. You could leave one unused (off) and wire the remaining three in parallel for on. Or 2 off/2 on.

Hope you find this helpful!
 

Thread Starter

TogetherInElectricDreams

Joined Jan 23, 2019
48
A little education. First, Ohms Law states that...
Volts = Amps * Resistance​
Similarly calculating Watts (W) has a similar equation...
Watts = Volts * Amps​
You know the pumps voltage (5) and it’s watts (3) so with a little rearranging, we can calculate the amps required...
Watts = Volts * Amps
Amps = Watts / Volts
Amps = 3 / 5
Amps = 0.6A​
That’s a little over the possible 1/2A limit, but under 1A. If your using a USB charger, I don’t think you’ll have a problem.

As far as the tap, I don’t think a dimmer will work. I suspect something like a PWM motor driver would be needed. But it doesn’t look like that pump is meant to be adjusted. Look into a rotary switch. There are two types. A lamp switch likely will only turn in one direction. Which is ok if that’s the desired action. I’ve provided a link to one example.

Then there are rotary switches that can be turned in both direction. A stacked deck rotary is an example of this. While it may have multiple contacts, you can wire them together for better action. I’ve provided a link to one example. This one has four contacts. You could leave one unused (off) and wire the remaining three in parallel for on. Or 2 off/2 on.

Hope you find this helpful!
Thank you! I do. No I wouldn't use the rotary on this pump, this one goes with the tap so I don't need it. It was my first solution for the first one I saw. Thanks for the equations! I can use them to work out a number of things now :-D
 

Thread Starter

TogetherInElectricDreams

Joined Jan 23, 2019
48
@djsfantasi I've used the equation you gave me to work out that my 12V / 4.2 W pump is actually 0.35A so I could actually power it with a USB and power bank too right? I've read other places that I can't though :-/

If I get a powerbank to power the entire kitchen, what considerations must I take into account? I am hoping that I can power all the elements from a rechargable powerbank so that the kitchen doesn't need to be plugged into the mains. I'll be running 2 LED strips, 2 Arduino nanos, a usb light plus the pump. I know that's hazy but I'm just wondering if that sounds like something I could actually do, I'd rather this than have four different power leads coming off it. Thanks again.
 

djsfantasi

Joined Apr 11, 2010
5,849
@djsfantasi I've used the equation you gave me to work out that my 12V / 4.2 W pump is actually 0.35A so I could actually power it with a USB and power bank too right? I've read other places that I can't though :-/

If I get a powerbank to power the entire kitchen, what considerations must I take into account? I am hoping that I can power all the elements from a rechargable powerbank so that the kitchen doesn't need to be plugged into the mains. I'll be running 2 LED strips, 2 Arduino nanos, a usb light plus the pump. I know that's hazy but I'm just wondering if that sounds like something I could actually do, I'd rather this than have four different power leads coming off it. Thanks again.
How are you going to power a 12V load with 5V? And where did you get the 4.2W number from?

I see that the device will work on a voltage range from 5V to 12V. So if you’re using USB, you are powering the pump with 5V. And my previous calculations apply.

I’ve never used the term powerbank. What do you mean by powerbank? Do you have a part number or link to what you have in mind?

To use all of those devices, you need to have the current draw of each of them. Plus anything connected. Depending on their length, LED strips can draw from a few hundred mA to several amps. Let’s guess 1.5A or 1500mA. Arduino Nanos might draw 30mA, but can drive 200mA of devices. What do you use the Nanos for? And the USB light (400mA)? How much current does that use? We know that the pump draws anywhere from 200mA to 600mA.

Adding up my blind guesses, I get 1500+2*200+400+600mA for a total of 2900mA. A 2500mAh USB battery pack would run for less than an hour before needing to be recharged.

I’m glad to help, but without specific numbers, it’s only a guess. I went through this exercise to show you wants needed to design s solution for you.
 

Thread Starter

TogetherInElectricDreams

Joined Jan 23, 2019
48
How are you going to power a 12V load with 5V? And where did you get the 4.2W number from?

I see that the device will work on a voltage range from 5V to 12V. So if you’re using USB, you are powering the pump with 5V. And my previous calculations apply.

I’ve never used the term powerbank. What do you mean by powerbank? Do you have a part number or link to what you have in mind?

To use all of those devices, you need to have the current draw of each of them. Plus anything connected. Depending on their length, LED strips can draw from a few hundred mA to several amps. Let’s guess 1.5A or 1500mA. Arduino Nanos might draw 30mA, but can drive 200mA of devices. What do you use the Nanos for? And the USB light (400mA)? How much current does that use? We know that the pump draws anywhere from 200mA to 600mA.

Adding up my blind guesses, I get 1500+2*200+400+600mA for a total of 2900mA. A 2500mAh USB battery pack would run for less than an hour before needing to be recharged.

I’m glad to help, but without specific numbers, it’s only a guess. I went through this exercise to show you wants needed to design s solution for you.
No that's fine, at least I'm starting to understand the calculations. I got the 4.2 W from the pump itself so I did your calculation with it. I need a 12V as the tap seems to have a connection only for 12V.

I really don't know what the draw will be from each item but let's take your calculations as a guide. What could my best bet be? Is there something similar to an extension lead that I can attach to the kitchen itself and then only have one plug going into the wall?

Sorry, I am gettting my terms confused: You recommended a 12V DC adapter. I am calling everything a powerbank these days, proves I don't know what the heck I'm on about!
 

djsfantasi

Joined Apr 11, 2010
5,849
No that's fine, at least I'm starting to understand the calculations. I got the 4.2 W from the pump itself so I did your calculation with it. I need a 12V as the tap seems to have a connection only for 12V.

I really don't know what the draw will be from each item but let's take your calculations as a guide. What could my best bet be? Is there something similar to an extension lead that I can attach to the kitchen itself and then only have one plug going into the wall?

Sorry, I am gettting my terms confused: You recommended a 12V DC adapter. I am calling everything a powerbank these days, proves I don't know what the heck I'm on about!
If you use a 12VDC power adapter, yes, you’ll only need one plug to the wall.

But you have to be sure that every device can work on 12VDC. Or feed power regulators/ buck converters to drop the voltage to the levels you need.

In order to be successful, you need to know the input voltage requirements of every device AND the current draw. I don’t have s comprehensive list of what you’re powering, so I can only make guesses. But the power adapters I am referring to supply several amps and possibly will supply everything you throw at it.

What you need to do is select an operating voltage. And then calculate based on that. In the example I provided, note that I calculated 0.6A. In your case, you changed to voltage. And hence, the amperage changed down to 0.19A.

Look at this link. It’s for a 5A power supply. That’s more than sufficient your your needs FOR A 12 VOLT POWER SUPPLY.

If some of your items need 5VDC, you’ll need power converters.
 
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