Looking back Your Pump doesn't say it's self priming, unless I've missed something.
EDIT: Also the dimensions of the pump say it's 1.1" (probably diameter) and about 3" high. Actually it says 2.9"L by 1.1"W by 2.9"H. I don't recall seeing a cylinder being mentioned as being 3x1x3. Diameter and Length yes. Unless it's very stubby at 3" diameter and 1" tall. These dimensions come from the MEASUREMENTS part of the page.

 

Correct me if I'm wrong but:

Holding both set and reset high will be occurring when the water reaches sensor 2. Only when it drops below set will the reset be held high. I always have had trouble following the logic of this device.

I am aware of that. The RS flip-flop is the basic solution to the problem, a starting point. It is not the complete solution. Illegal states have to be taken into account for a working solution.

The simple solution is:

1) When both sensors are active (ON), the flip-flop is SET.
2) When both sensors are inactive (OFF), the flip-flop is RESET.

 

While you all were talking I drew up this diagram (with a DPST relay). Looking at it I should have labeled pos and neg. Red is positive.

That would be a 12v relay? And the diode 1n4001?

I have a bag of 12+ different relay's to choose from. Must have something there I can use.

 

I'm not confident a 12V relay would be the best. If you can find a 9V relay that would be better. Even at 7.2V a 9V relay. should pull in. As for the diode - sure. A 1N4001 should do just fine. DPDT works the same as a DPST. You just don't have the NC contact.

 

If your sensors have NO-COM-NC contacts and you have a latching relay, you can do it without electronics.

Edit: New solution. Sensors are NO (Normally Open). Relay has to have two poles, DPST (Double Pole Single Throw) will work.

 

Looking back Your Pump doesn't say it's self priming, unless I've missed something.

I asked Amazon Rufus. Answer is...
Rufus is generating a response...

The LZKW 3-6V Water Pump is designed to be self-priming - it can pump water continuously once operational. The pump features:

• Direct water submersion: You can place it directly in water and it will start working
• 15-hour continuous operation: Under 5V conditions, it pumps water continuously without interruption
• Variable flow rates: 1.1L/min at 3V, up to 1.8L/min at 6V
• Plug and play design: JR connector plugs directly into RC receiver

The pump is specifically designed for RC boats that need water cooling systems and operates effectively as a self-priming unit for marine applications.

There are other low voltage pumps on Amazon that say self priming so I'll have something like that. I don't have the pump yet, I do have a crap load of electronic parts. Should be able to find something.

I'll need some time to go through my parts and see what I can come up with and breadboard something.

 

Why dont you use a single float and switch with the hysteresis in the switch actuator, like a sump pump? The switch can energize the pump directly, without any relays or electronics.

 

Are float switches reliable if the boat is heeling?

 

Keithwalker, I like that idea, but with the small space available, I don't think the float will be large/strong enough to have enough strength to move a toggle switch, unless there is something else that can be used.

Alec, perhaps not, but the boat will not be heeling all the time. If probes are used to detect water then there is no issue about heeling.

Here is a video of the boat I am building. That is some else's boat, not mine,

 

Certainly the concept is valid, and I understand that the boat may heel quite extremely.
The circuit in post #11 will work with a 12 volt pump motor. The circuit in post #25 will allow the float switch contacts to only power the relay.

 

Got it, thanks.
Next week I'll make a test run on what I have on hand, just to verify operation. And I'll order whatever I need specifically for what will go in the boat.

 

I'm testing with the components I have on hand. I don't think any of the relay's I have are latching.

For sensor#1 I'm using an on-off switch.
For sensor#2 I'm using a momentary switch.
The relay is Omron G5V-2. And a 1N4001 diode.
Finally a 12v battery. I have it wired up in the diagram below.
For the pump I'm just using a voltmeter.

With the on-off switch (sensor#1) being off, no water in the boat, no voltage on the meter. CORRECT
With the on-off switch (sensor#1) being on, water is in the boat, no voltage on the meter. CORRECT
When water reaches the momentary switch (sensor#2), I press and hold the momentary switch, the meter indicates 12v. CORRECT.
As the water drops, release the momentary switch (sensor#2), the voltage changes to zero. INCORRECT

So unless I have the circuit wired wrong, or using the wrong relay, this is not working as expected.
Will have top now try the setup in post #25.

 

f your sensors have NO-COM-NC contacts and you have a latching relay, you can do it without electronics.

Edit: New solution. Sensors are NO (Normally Open). Relay has to have two poles, DPST (Double Pole Single Throw) will work.

Not fully understanding this.

 

In order to simulate the sensors, you need to use ON/OFF switches, not push-buttons.

 

I don't get why there are two switches. Why not just one?

 

It should work the way I have it. As water rises, the first switch activates and stays on until after the water recedes, thats why I used an on-off. As the water hits the momentary switch, that switch would activate the pump, then the water will drop and the momentary switch deactivates, and the pump should stay on. Then once all the water pumps out, the on-off switch would turn off. I'm using the on-off to simulate sensor#1 being constantly on until all the water pumps out. The momentary switch would just trigger the pump to go on.

Yes? No?

Ulms..... with one switch the pump will be constantly be going on and off, on and off. With two switches it will allow a little water to accumulate before the pump goes on, so that there is no constant cycling of the pump.

 

Searching online, I came across this circuit. I added the relay pin connections. With the on-off switch for low and momentary switch for high it works perfectly. This is with a 12v relay. Now I need to find a 5v relay for the 3-6 volt pump.

 

Question if anyone can help. I have a 5v dual coil DPDT relay. Specifically G6AK-234P-ST-US . So this is a latching relay. I'm not sure how to wire this up in my pump setup, if it is useful. I'll search online to see what I can find in the meantime.

 

A single coil self latching coil needs a positive to latch it. Then the power can go away and the relay stays latched. To unlatch it you need to apply a negative to unlatch it. It's called Set/Reset latching type. Give me a few seconds and I'll post a picture of your relay.

 

Pins 1 & 16 are the relay coil. Positive on pin 1 and negative on pin 16 will set (latch) the relay. Reversing the connections: Negative on pin 1 and positive on pin 16 will reset (unlatch) the relay. You don't want to use a latching relay, it will require a bit more working on developing a set and reset signals.
WRONG DIAGRAM EDITED OUT. SEE POST #42
Bartholomew Jojo Simpson (not really)