Pressure switch output??

[johndeverill]

Hi,

I have an SMC digital pressure switch. Basically it has three wires +,- and output. I want a 12v solenoid to activate upon reaching a set pressure. This is being used in a car. I connected it all up to the 12v battery. I then connected the output to a multimeter. All seemed fine, no signal in the output wire until the set pressure was reached and 12v was recorded in the output wire. Great, I thought. So I connected up a 12v DC solenoid....+ve to the output wire and -ve back to the battery terminal. Upon pressure being reached the switch threw up an overcurrent error that the troubleshooting guide says is due to a short circuit. So I tried with the multimeter again and all seemed OK. MM -ve connected to battery -ve. Am I missing something fundamental here? Do I need to connect the solenoid -ve to the body ground as opposed to the battery -ve?

Thanks in advance

John

 

[EdwardM]

Hi

can you post a data sheet for the DP switch?, it may be that there is insufficient current avaiable or something else.  If you can provide a sketch of your circuit, that would be helpful too

Best of Luck

Ed

 

[johndeverill]

Hi,

Here's how it all connected

 

[EdwardM]

Hi John,

you haven't said which SMC switch it is but looking at some of them it appears that the output current available is less than 80mA which means that you could drive a small relay (solenoid) and use its high current contacts to drive something bigger, it really depends on which switch you have and the power needed by your solenoid.  SMC seem to do a hugh range and some are PNP and some NPN open collector output.

Really need to know which one

Ed

 

[johndeverill]

Hi Ed,

AFAIK it's the ISE4B PNP.

Cheers

John

 

[EdwardM]

Hi John

circuit as shown below.

To reiterate, max current into load is 80mA which aint much so you may need to drive a small relay or transistor first to make your solenoid work. (If you need help with that, come back)

Best of Luck

Ed

added second drawing just in case

View attachment 37078

View attachment 37079

 

[johndeverill]

Hi Ed,

That's great. Ill give it a try.

Many Thanks

John