Need a time delay circuit for my float switch and 12v pump?

[AquaHydroChem]

Hi

I need a time delay circuit, had a look on the internet and could not find any for sale
So I probably need to build a time delay circuit that when the float switch closes (opens the circuit) there will be a time delay from when the pumps turns on
And/or when the float switch opens (closes the circuit) there will be a time delay from the pump turning off
And the time delay must be started and reset from the switch opening and closing not the circuit to have a set time regardless of what the switch is doing

The reason I need this is to stop the constant on/off cycle of the pump turning on and off with the float switch bobbing up and down on the water surface as the mixer tank is being filled and emptied
The mixer tank is supplied by a 12 volt 5 amp pump controlled by the float switch and has a max switch of 0.5 amp
The tank is emptied at the bottom by a drainage tap and water being drawn from the tank to a high pressure pump

I am working on a ball park figure of a 10 second delay from when the float switches and the pump starts or stops
This will probably have to be tweaked once the time circuit is build and fitted to the mixer tank and once I have seen how it fills and empties in the tank

A believe there is the ‘NC555’ chip and the ICM7555IPA chip that can be bought from maplins
But maplins don’t sell a complete circuit
Please note the only electrical experience I have is with 12 volt plug and play and recently relays
So diodes capacitors and resistors is all new to me
If possible could someone post a diagram of how to wire the NC555/ ICM7555IPA up and wear it should be placed in relation to my schematic

Thanks

 

[AquaHydroChem]

fs

• AquaHydroChem
• 12 Feb 2009
• 1

 

[RF Lighting]

12V Multi function timer relay

RS part number 385-6957

 

[Chris.J]

Google for TKT330.

 

[Spark123]

Why not have 2 float switches, lower one to enable a latching relay and a upper one to switch it off?

 

[bernardgreen]

Why not have 2 float switches, upper one to switch enable a latching relay and a lower one to switch it off?

Beat me to it.

Using a latching relay ( or contactor with a contact wired to latch ) is a far better way to achieve the end result when controlling tank filling or emptying.

 

[ban-all-sheds]

Why not have 2 float switches, lower one to enable a latching relay and a upper one to switch it off?

I thought that's what he did have.....

 

[Spark123]

That's odd, that is the very thread I was thinking of when I drew this:

Untitled

• Spark123
• 12 Feb 2009
• 1

 

[AquaHydroChem]

the tkt330 Seams to be use for burglar alarms
will the time intervals be regulated by the switch and not the TKT330.will it
reset its self when the switch opens and closes
and wear would I wire it into my schematic
My schematic has a rely would I have to do away with it

Hear is wear I sourced the info on the 555 timer
http://www.reuk.co.uk/Water-Pump-Hysteresis-Circuit.htm
But cant relay work out how it fits together and the guy never relay got back to me about it

Sorry spark123 the 2 float switches in the mixer tank never rely worked
No matter what I did the lower switch just kept welding/arching together to the point now wear ist knackered and can’t be reused
I had a man from switch and sense draw me a diagram of how to wire both switches into 2 different relays all that happened is when the water reached the lower switch it switch on and off all the time eliminating the point of have an upper switch

 

[Spark123]

The only reason for the switch welding would be too much current flowing through it owing to ommitting the diode or a spike caused by the voltage caused by the relay switching off.
This can be overcome by fitting a reverse biased diode across the relay coil:

Untitled

• Spark123
• 12 Feb 2009
• 1

So all you need are 2 switches, a couple of 1N4001 diodes and a 12v relay!
Having 2 relays should have worked too, ignoring the spike mentioned above the the 2 relay coils would have been wired in parallel, one relay used for control and the other to switch the pump.

 

[ban-all-sheds]

the tkt330 Seams to be use for burglar alarms
will the time intervals be regulated by the switch and not the TKT330.will it
reset its self when the switch opens and closes
and wear would I wire it into my schematic
My schematic has a rely would I have to do away with it

I think that for as long as you don't understand relays, timer circuits, basic electronics etc you're always going to struggle to design and build something yourself.

Sorry spark123 the 2 float switches in the mixer tank never rely worked
No matter what I did the lower switch just kept welding/arching together to the point now wear ist knackered and can’t be reused

Wasn't that a proper commercial control system?

There was a properly printed schematic - where did that come from?

Surely unless you're carrying out some industrial process which hardly anybody else has ever done there must be an off-the-shelf system you can get which will turn a pump on and off in the manner you describe?

 

[ericmark]

I have tried doing this using PLC and I found the expected time required was different to really required.

But timers are available of course designed to work star/delta starters etc.

There is also mention on the NE555 timers and if you want to play I can help with the circuits.

I am lucky I have electronic workbench loaded on my PC so I can test without building.

See http://www.uoguelph.ca/~antoon/gadgets/555/555.html on how they work with simple system it is not too bad to build on variboard which is a load of copper strips with holes drilled poor mans printed circuit but the current output from a 555 is very low.

 

[AquaHydroChem]

[quote="ban-all-sheds";p="1137834
Wasn't that a proper commercial control system?

There was a properly printed schematic - where did that come from?

Surely unless you're carrying out some industrial process which hardly anybody else has ever done there must be an off-the-shelf system you can get which will turn a pump on and off in the manner you describe?[/quote]

the original schematic I posted cane from the manual it self

I found this from maplins http://www.maplin.co.uk/Module.aspx?ModuleNo=25224
but Im unsure if it all do the job or and when I phoned maplin they didn’t rely know ever
all they could give me was this link www.velleman.be/downloads/0/manual_mk111.pdf
but that just tell you how to build it not what it dose

 

[breezer]

why not put a lead weight on the float switch?
The idea being to "dampen it"

On the other hand there are probably quite a few ways to do what you want, but as you know little about what you are doing and how it works, (I know you want to learn) but i would suggest its time you aproached a contols company to make one for you.

 

[ericmark]

Sorry do you want the fun of self build or would you prefer an off the shelf unit?