SOLVED--Is it possible to break a circuit by closing it?

Hello,

I'm hoping to modify a simple circuit but I'm not sure what I have in mind is possible without replacing one of the main parts.

The application was for adding water to two rechargeable banks of 2 volt batteries, a process that took a very long time pouring from a watering can, which had to be refilled every couple of batteries (there are 48 batteries in total). I salvaged a washer fluid tank from an old vehicle (which would be fed from a larger container) and ran some tubing from it long enough to reach all the batteries. Then I wired a trigger to the pump so I could control the flow as I was filling each battery. This has worked fairly well for the past couple of years. The problem is that holding the trigger tires my finger quickly, and this process usually takes between an hour and 90 minutes.

What I am wondering is if it's possible to reverse the function of the trigger by adding 2-way or 3-way switches (or some other method), so when I pull the trigger the flow stops to move between cells and batteries. Is it possible to break a circuit by closing it?

Thanks.

There are push-button switches that break the circuit when pushed.

A normal stop button will do that.

Alternatively you could use a relay or a transistor circuit to stop the motor when the button is pressed.

Thanks for your reply. In this case the switching would happen by closing the circuit with the trigger, so the push buttons wouldn't work here. A mini relay could work though. I'll look into this idea further. Thanks!

Sounds like you need a 'push to make; push (again) to break' switch. Otherwise known as 'latching' or 'maintained' switch.

Something like this might work, though you might need something that can handle a higher current.

A rotary timer powering a wall wart might be a possible solution. Along the lines of "this battery looks like it will need 10 mins of water" - set timer to 10 mins and walk away.

Another possibility is to replace the trigger with a toggle switch.

Mike.

Buk said:

Sounds like you need a 'push to make; push (again) to break' switch. Otherwise known as 'latching' or 'maintained' switch.

Something like this might work, though you might need something that can handle a higher current.

Click to expand...

I have the tubing attached to the top of the trigger, so I can operate it one-handed, point-and-shoot style. I would like to keep that form factor and I'd rather not try to modify the trigger with the push-button. Had I known this is the way I was going to end up going, I would have looked for a latching or even a toggle trigger instead of the momentary switch. Hindsight, etc., etc.

I think a relay will be the best option. I'll add a 3-way switch after the 87 and 87a contacts and use it as the main switch. One way will be powered off unless triggered, and the other way will be powered on unless triggered.

Could you make a mechanical latching arrangement for the trigger, e.g. rubber band, wire hook, ...... ?

If you have to add water to the batteries frequently, then it sounds like you are seriously overcharging, and possibly damaging them.

Coronos said:

I have the tubing attached to the top of the trigger, so I can operate it one-handed, point-and-shoot style. I would like to keep that form factor and I'd rather not try to modify the trigger with the push-button. Had I known this is the way I was going to end up going, I would have looked for a latching or even a toggle trigger instead of the momentary switch. Hindsight, etc., etc.

I think a relay will be the best option. I'll add a 3-way switch after the 87 and 87a contacts and use it as the main switch. One way will be powered off unless triggered, and the other way will be powered on unless triggered.

Click to expand...

A picture of the hand held unit would help us understand the mechanical constraints. Also, what voltage does the pump run on?

As for the relay, I would use a latching relay that alternates on/off for each push of the trigger. Here is one possibility.

https://www.amazon.com/HiLetgo-Sing...keywords=latching+relay&qid=1641330465&sr=8-3