12V Simple timer

Thread Starter

manugoss

Joined Apr 23, 2019
7
Hello all. Simple question for a newbie. I wish to control a solenoid valve for a water pump that runs on propane gas (LPG). The solenoid valve is normally closed. The water pump is used for irrigation/fertigation where the pump must run for fixed amount of time ex: (30min, 45min 60min etc) In a perfect world, I would set an analog timer for 45 min for example, start the engine and the valve would stay open for that 45 min, the valve would that shut and the engine would die and be ready for another its next task.

Only have access to car battery. I looked into omron H3Y 12v timer, can this be achieved with the 0-60 min dial and a simple on/off switch to activate the valve at the beginning? I looked into programmable electronic system but seems a bit complicated for application where the duration changes constantly.

This will be run mostly by my father and a dial with number and switch would be complicated enough for him. Thank you all for your input, all this electronic is not my field of expertise and I am sure someone here will have great input for me.
 

dendad

Joined Feb 20, 2016
3,427
Do you want the timer to start manually with a pushbutton, run for the settable time period then stop until the button is pushed again?
Or do you want the run time and repeat period settable?
This could be a good start into an Arduino project for you.
https://randomnerdtutorials.com has really good instructions.
 

AlbertHall

Joined Jun 4, 2014
9,628
The water pump is powered with propane?
The timer switch is to control a water valve on the output of the pump?
Would that also somehow switch off the pump?
 

Thread Starter

manugoss

Joined Apr 23, 2019
7
Thanks for the replys.

Basically, the timer controls the solenoid valve, for the propane fuel, Basically a shutoff valve. It is a simple honda gx engine but with dual fuel carburator. The solenoid valve must be open for the engine/pump to run, allowing fuel to run through the engine.. When the solenoid is closed, the engine dies instantly.

I want a timer just like a microwave or a dryer timer: you set the time, press start and it runs until times run out. The valve is normally closed so it must be powered for the duration of the run time. No fancy repeat programmable etc, no push button to stop. Every run is a diffrent time it could be 20 min or 60 min for exemple. It could be digital or mechanical for the timer but it must be easy to setup just like a house appliance for exemple. A turn knob would be even better. I hope it is all clear as mud now.
 

dendad

Joined Feb 20, 2016
3,427
If you can find an old clockwork timer from a dead microwave oven that would work ok. And be very easy to work.
I would make something with an Arduino myself, so that could be worth having a go if you are so inclined.
 

Thread Starter

manugoss

Joined Apr 23, 2019
7
Dendad, would a microwage clorkwork be strictly mechanical? If so,I guess that it would be indeed very easy to setup in terms of electronics...
 

dendad

Joined Feb 20, 2016
3,427
Dendad, would a microwage clorkwork be strictly mechanical? If so,I guess that it would be indeed very easy to setup in terms of electronics...
Some are.
Try try an old one, see if it ticks when the power is off, and the knob slowly returns to home.
Our ironing cabinet has one of those too. Purely a clockwork mechanical timer switch.
 

Thread Starter

manugoss

Joined Apr 23, 2019
7
I really like the idea of a mechanica timer but unless I find old appliances, it might be hard to find so kind of challenging in terms of part sourcing in case of failure. If I was to go with the Arduino, how easy would it be to setup the timer for each run? Thanks
 

dendad

Joined Feb 20, 2016
3,427
Whatever way you go, make sure there is a reverse diode across the valve coil...

Solinoid Switch.jpg
An Arduino timer is pretty easy to make.
Do you want a display, or just a knob with markings on the case?

A setting knob, Start button, a Stop button and an optional display.
The Arduino can read the knob position and set the delay from 30 to 60 mins. Then push the start button.
A stop button can be for emergency stop.
Also, having the Arduino will allow added features, like stopping the motor if it runs out of oil, overheats.....
 

AnalogKid

Joined Aug 1, 2013
8,377
Even at only 12 V, appliance timer switch contacts might have a reliability problem switching DC. What is the current rating of the solenoid coil?

ak
 

Thread Starter

manugoss

Joined Apr 23, 2019
7
Analog kid, The rating of the solenoid is 0.8 A for 12 VDC.

dendad. I looked into the arduino and seems like a lot of fun. With the basic arduino uno, a display and keypad it seems like I could technically make it work.
A few questions:
1) Parts seems available cheaply from ebay from China: Can those be used or it is too cheap?
2) Could the arduino output lets say 1.5A @12vdc or would I need something else to power the valve?
3) If the power is turned off from the arduino uno, will it ''remember'' the program once it is powered back on?

I am looking at some 12V timer form ebay that are equiped with display and seems like it could work also instead of going the arduino way and buying seperate parts. What is your toughts on this?

Thanks alot for all your inputs
 

dendad

Joined Feb 20, 2016
3,427
Analog kid, The rating of the solenoid is 0.8 A for 12 VDC.

dendad. I looked into the arduino and seems like a lot of fun. With the basic arduino uno, a display and keypad it seems like I could technically make it work.
A few questions:
1) Parts seems available cheaply from ebay from China: Can those be used or it is too cheap?
I use them quite a lot.
The Unos for around $5, and the LCDs for a bit less.

2) Could the arduino output lets say 1.5A @12vdc or would I need something else to power the valve?
You will need a FET or relay board to drive the valve as the Arduino can only produce enough current to control the switches, not switch the load directly.

3) If the power is turned off from the arduino uno, will it ''remember'' the program once it is powered back on?
Yes, it will.
I am looking at some 12V timer form ebay that are equiped with display and seems like it could work also instead of going the arduino way and buying seperate parts. What is your toughts on this?

Thanks alot for all your inputs
That may well work too. But it may not, depending on the design. And, it will not be as customizable as a DIY Arduino.
 

rphare

Joined Nov 20, 2015
9
What are your goals here? if you want to have some fun, learn a few things, and are willing to fiddle with your design to get it working, consider the Arduino or some other DIY electronic approach. If you simply want to get the job done and make your dad's job easier, buy a mechanical countdown timer/switch. Turn the knob to the desired number of minutes, start the engine, and the valve will close after the time expires.
You don't need to find an old microwave; they're available at Lowes, Home Depot, Graingers etc.
Example: https://www.homedepot.com/p/Woods-20-Amp-60-Minute-In-Wall-Spring-Wound-Countdown-Timer-Switch-Almond-59718WD/203638997
HTH
 

Thread Starter

manugoss

Joined Apr 23, 2019
7
rphare Good point on what are my goals. I am very tempted to go the arduino road and play with electronics and programming and keep the mechanical switch as a plan B. I found alot of info on arduino and even specifics on solenoid valve on youtube:


Will keep you posted but probably will have more questions as I go deeper into my research and fiddling.

Thanks
 

Thread Starter

manugoss

Joined Apr 23, 2019
7
Dendad, You suggested using a reverse diode. After watching this youtube video I kind of understand why. He is referring to flyback or snubber diode. Is there a way to know which one to use size wise? Would any model work? Thanks
 

dendad

Joined Feb 20, 2016
3,427
Dendad, You suggested using a reverse diode. After watching this youtube video I kind of understand why. He is referring to flyback or snubber diode. Is there a way to know which one to use size wise? Would any model work? Thanks
My rule of thumb is to have at least the coil operating current rating x2, and more if you can. Diodes are cheap, so use the 3A one I mentioned. You do not want it to fail.
 

SamR

Joined Mar 19, 2019
2,018
When you said LPG my alarms went off. You just stepped into the realm of an electrically classified hazardous environment requiring explosion proof design and devices.
 
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