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Help needed with a (very) basic project

Mathieu86

New Member
Hello,

I don't have much knowledge in electronics but I need to figure something out.

I have a valve that is controlled by a small motor that is connected to 12v with a switch. The switch is the one shown on the pictures below. When pushed one way it opens the valve (until it is released), when pushed the other way it closes the valve and when left in the middle it doesn't do anything.

H0bb8a6d243674b23b378d01065b235cdd.jpg switch.PNG

The problem is that I don't want to use that switch. It is first big and ugly but also unpractical. I want a switch with one position ON and on position OFF, like the ones below.

H5bcd9101fd7f4228a922aae33125f340G.png

I need something to come in between that would act in such a way :
- when I flip the switch from 0 to 1 -> it activates the motor for 2 seconds to make sure the valve is open then it stops sending current to the motor
- when I flip the switch from 0 to 1 -> it activates the motor for 2 seconds the other way around to make sure the valve is closed then it stops sending current to the motor

I found this item on Aliexpress that seem like it might help but I'm not sure if it wil work or how to set everything up :


I'm quite sure on the other hand that my problem is quite basic and can be solved with a few items from Aliexpress for a small budget, I just don't know what to buy.

Any help would be appreciated ! thanks in advance.


Mathieu
 

gophert

Well-Known Member
Most Helpful Member
It is not as easy or common as you suspect. I assume it is 12VDC. Do you know how much current the motor draws or, the "stall current"?
 

dougy83

Well-Known Member
If you get a switch with three contacts, you can use two delay relay boards to control the valve in each direction.
valve drive.jpg
A RC snubber should probably be connected across the valve coil, or you could use four diodes to shunt any spikes to the 12V supply.
 

Mathieu86

New Member

dougy83

Well-Known Member
dougy83, can I order all of that easily ? Do you mean a switch with 3 positions and 6 pins ?
I meant a switch with two positions, and three pins. They are called SPDT (single pole, double throw), but you could use a six-pin switch if you wanted.

It would be amazing if I can use this switch :
The item description shows how to use it and it looks it's also just an on/off type of switch
It looks like that switch has three pins for the switch (normally open, normally closed, and common), as well as two pins for the backlight. You should be able to use that with the diagram I showed.
 

dougy83

Well-Known Member
Do you have any data for that Time Relay Module? I have a feeling that it will require contact closure to make it start timing. A delay on-time relay is warranted (one that automatically starts timing when power is applied). They do exist as modules
 

Mathieu86

New Member
Okay, I just bought everything. Thanks a lot for your help. It will take some time to be delivered but hopefully I can manage with the drawing you sent :)
 

dougy83

Well-Known Member
Good luck!

Your switch has an indicator in it.
  • If you want it to light up while the motor is on, you can connect a diode from each side of the motor to the positive terminal of the indicator (i.e. two diodes total). The negative terminal of the indicator goes to GND.
  • If you wanted it to light up when the switch is in a particular position, you'd connect the indicator positive terminal to one of the switch outputs, and the indicator negative terminal to GND.
 

shokjok

Member
Have you considered a relay-free motor driver circuit with four transistors connected as an H-ladder, driven by a delay timer feeding a center-off DPDT switch? The other switch contacts would supply power to this circuit. I'm without a drawing at this time, as I'm designing a motor speed control circuit with a 4011, 4029, and R-2R ladder feeding a LM308 or LM393 op amp driving a MOSFET to control the blower fan motor, eliminating the blower fan resistor.
 

Mathieu86

New Member
Hello !

Thanks for your answer ! I however don't understand most of it o_O. I already bought the components that dougy83 recommended, they should arrive soon. If that doesn't work then maybe I'll ask you for more details on your solution.
 

gophert

Well-Known Member
Most Helpful Member
A center-off DPDT switch is what you want for this project.
That is what he has now and the specific point of the project is that he wants a simple on/off switch. But, he did say he wanted to get rid of the center-off DPDT switch because it was ugly. I'm not sure he know that beautiful rocker-style switches are available to replace his existing switch and will function exactly like the existing switch - a direct replacement.




 

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