How to Randomly Pulse a 24VDC Solenoid Valve Without a PLC for Spray Marking

Hi,

I am trying to time a solenoid valve to open sporadically on a machine so that the driver has a way of knowing what he has and has not done. The solenoid is tied into a spraying system that when on sprays a white line... the exact time of on and off is not important only that it turns on and shuts off long enough to leave a noticeable line but turns off so that it does not use a lot of material. In school I would have used a PLC to do this however I do not have the resources to do that here. What is the easiest way to do this and how do I go about getting the components. The solenoid is a 24VDC.


Thanks

That seems like a good application for a 555 timer. You can find many reference circuits and discussions about how to configure them for various on/off times by using simple resistor and capacitor combinations.

Then, you could use the output of the 555 to drive a BJT or a MOSFET which can switch the solenoid open and closed. Be sure to include a freewheeling diode since you are driving an inductive load; again, many references on the internet for this if you search on those keywords.

All of these components are readily available from places like Digikey, Mouser, etc. You could do all of this with thru-hole parts on a solderless breadboard so you can fiddle with it until it works the way you want.

Alternatively, you may find a simple circuit already available that flashes a light or something (an adjustable strobe light from Spencer's for under $20 comes to mind), and then you could just replace the light with the BJT/MOSFET and diode to drive your solenoid.