pump test rig simple controler

[rafal2013]

Hi guys.

I need to put together a simple controller for an air powered water pump. I wondered if one of you would be so kind and advise on the correct way of doing it?

I've attached a sketch of the pump and basic connection schematics. Also attached is data sheet of the level sensor we'll use.
The solenoid valves' coils are 16W each. The sensors can be either direct load or PNP. The controller's job is to close the vent and open the air supply once the water level reached the top sensor, and close the air supply and open the vent once the water level has been brought below the bottom sensor (the air supply valve is Normaly Closed, the vent Normaly Open) This would be one pumping cycle. 10 million cycles is expected over the lifetime.

My question is: what would be the best option:
- use direct load sensors to drive a relay
- use direct load sensor to drive solid state relay
- use PNP sensor to drive (what)?

Thanks
Rafal

 

[ericgibbs]

hi rafal,

Your 16Watt solenoids, what voltage rating are they.?

E

 

[rafal2013]

hi Eric,

I'm sorry, I forgot to mention this is going to be supplied with 24DC.

Rafal

 

[ericgibbs]

hi Eric,

I'm sorry, I forgot to mention this is going to be supplied with 24DC.

Rafal

hi,
Thats approx 660mA per solenoid valve, the level sensors for the PNP and Direct are rated at 500mA max

As its a 24Vdc system I would use 24V relays contact rated 3A to 5Amp

Use the PNP type to drive a relay for each solenoid.

E

 

[rafal2013]

Thanks for the reply Eric.
I think the direct load is actually 5A but I can't see how I would be able to achieve the required operating driving the solenoids with the sensors directly, hence the relay.
I've actually already got a relay which is 5A on the poles, the coil of the relay is rated at 38mA so as you said PNP would be sufficient.
I've read however that solid state relays last much longer and with the 10 million cycles here I thought it could be a good option, providing it is doable?
Is there any other way I could control the valves?

Rafal

 

[ericgibbs]

hi,

If you prefer solid state relays, you connect 24Vdc to a contact pin of level detector and a suitable value resistor on the output pin, this would drive an SSR.

Most SSR will accept 3V thru 30Vdc as a controlling voltage, usually they require approx 5mA to 10mA.

So the resistor would be 24v/.01 = 2400R say 2.7K

The common side of the SSR control pin would be connected to 0V of the 24Vdc power supply

Do you follow OK.
E

 

[rafal2013]

Many thanks for your help Eric.
Unfortunately my knowledge of electronics is very basic if any...
If I understand correctly you mean to connect the PNP outlet of the sensor with the 'control' terminal of the SSR?
If so I don't understand why I would need a resistor there? It sounds I would actually need two SSR to substitute the switches on the schematics and to drive the third SSR which would switch the solenoids?

Rafal

 

[KeepItSimpleStupid]

If you want to design with reliability consider a real solenoid driver approach such as these circuits: https://electronicdesign.com/analog/what-s-all-solenoid-driver-stuff-anyhow

There are IC's specifically designed to drive solenoids and/or injector drivers.

These need a kick to get them moving and then the voltage is reduced to a hold mode. Everything benefits.

I once designed a driver for a Leedex rotary solenoid used as a shutter and my other shutter driver I used a Velleman PWM motor controller Kit directly. The soft-start slowed down the activation which is what I wanted. cycle time was about once every 2 minutes on/30 s off for a 7 hour day.

 

[ericgibbs]

Many thanks for your help Eric.
Unfortunately my knowledge of electronics is very basic if any...
If I understand correctly you mean to connect the PNP outlet of the sensor with the 'control' terminal of the SSR?
If so I don't understand why I would need a resistor there? It sounds I would actually need two SSR to substitute the switches on the schematics and to drive the third SSR which would switch the solenoids?

Rafal

hi.
Your drawing shows all the relay contacts operating from a single relay.?

How many solenoids will you have in total and it what sequence do you want them to operate.?

A single SSR can switch 10Amps.

Have you an SSR type you prefer?
E

EDIT:
These are typical, but a little price.
https://uk.farnell.com/jsp/search/b...arametricAttributeId=&prevNValues=2031+203128

 

[rafal2013]

If you want to design with reliability consider a real solenoid driver approach such as these circuits: https://electronicdesign.com/analog/what-s-all-solenoid-driver-stuff-anyhow

There are IC's specifically designed to drive solenoids and/or injector drivers.

These need a kick to get them moving and then the voltage is reduced to a hold mode. Everything benefits.

I once designed a driver for a Leedex rotary solenoid used as a shutter and my other shutter driver I used a Velleman PWM motor controller Kit directly. The soft-start slowed down the activation which is what I wanted. cycle time was about once every 2 minutes on/30 s off for a 7 hour day.

Thanks for the link KeepItSimple. It's a really interesting option, not sure if I'll be able to put it together without any electronics knowledge but might have a go anyway! This is just a test rig at the moment but will end up an industrial application. We'll probably have professionals design a proper logic box for the product itself.