How do I pulse 24V?

[tigertracker]

I am trying to rapidly turn a solenoid on and off. I would like to do it at 5-10 Hz. If I understand correctly that should be 5-10 on/off cycles per second. Currently I have a switch mounted in a small project box from radio shack and when I turn the switch on, the solenoid activates. That is pretty much the limit of my knowledge which is why I'm here. I also will not know alot of the abbreviations that many of you may use, so please explain on an beginner level. I contacted an electronics store the other day and the guy told me I need a 24V pulse relay, but that there were other ways to do it. He could not tell me how to build the relay, where to buy one, or how to set the frequency. I would like to be able to adjust the frequency, but I can manage without that. Can anyone help?

Thanks

 

[blueroomelectronics]

What are you trying to build?

 

[Andy1845c]

Yeah, like Bill said, what is this for?

How big is the solenoid? How much current (amps) does it draw? Is the 24v AC or DC?

This should be fairly easy to do.

 

[tigertracker]

I am trying to build a device that will bypass an irrigation controller and activate the solenoid that opens a valve. The irrigation controller runs off 110V power. That power runs through a transformer that steps power down to 24V to turn the solenoids on and off. Currently I have 2 alligator clips on a switch. One clip runs to the wire just behind the 24V transformer. The other clip bypasses the controller and clips to the solenoid wire. When I throw the switch, the 24V passes down the wire to activate the solenoid. When I throw the switch I want it to pulse the 24V signal at around 5-10 Hz.

 

[tigertracker]

It is 24V AC and the solenoid has 50/60 Hz stamped on the side. I am not sure what the amp draw is, maybe my other reply will help. If I can check that with a multimeter I will do so tomorrow.

 

[blueroomelectronics]

Depending on the solenoid 5 to 10Hz may simply keep it on or off. Why do you want to pulse them? You may even wear them out quickly if they do pulse on and off and weren't designed for it.

 

[tigertracker]

I am pretty sure they were not designed to to work that fast. If they fail that is OK. I just need it to work for about 5 minutes without failure. I know that they will activate a few times per second as I can do it manually. Just can't keep that up for 5 minutes Yes, 10 Hz may just keep it on, that is why I need to make it adjustable if possible, or if it is cheap enough, I may build a few frequency options to see which one meets my needs. I may find out that 2-3 Hz is more the range I need.

 

[blueroomelectronics]

Why not just use an impact sprinkler head?
**broken link removed**

 

[Andy1845c]

Well, I was thinking somthing along the lines of a 555 timer driving a optically isolated solid state relay. The relay would be used to switch the 24vac.

The net has alot of 555 timer information. The frequency and duty cycle can be adjusted.

Why can't you just open and close the solenoid? I understand it operates a valve? I doubt thats ment to be pulsed..... Are you trying to pulse it to control the volume of water?

You only need it to work for 5 minutes? Why go though all the effort of building a circuit for 5 minutes of use?

 

[tigertracker]

I want to improve upon this device

**broken link removed**

The chatterbox runs off of a 9V battery and you cannot vary the frequency of the chatter. I want to run it off the 24V supplied by the irrigation timer and vary the chatter frequency.

 

[blueroomelectronics]

Well that simplifies things, I'd bet the chatterbox is little more than a 24V relay and a capacitor.
Much like the relay and cap in this diagram.
**broken link removed**

 

[tigertracker]

the chatter does not come from a speaker. It comes from the sound the solenoid makes as it turns on and off. When one of our irrigation techs need to work on a valve, sometimes grass has grown over the cover (they are buried in boxes underground). We can either track the wire from the clock to the valve with a wand and headset by sending a tone down the wire (somewhat time consuming as tone gets lower the further away you get) or listen for the chatter. I assumed 24V power would make the solenoid open and close with a little more force, thus increasing the sound effect.

 

[blueroomelectronics]

Actually I the relay with the cap would work with a solenoid. Ignore the speaker and transformer, the battery is supplied by your current sprinkler system.

 

[Andy1845c]

I assumed 24V power would make the solenoid open and close with a little more force, thus increasing the sound effect.

What voltage are they designed to work with? I wouldn't exceed what they are designed for. Raising the voltage may make them louder, but will also be hard in them. The coils could also overheat.

 

[tigertracker]

can you explain what the abbreviations in your diagram mean? Does this have to be on a circuit board or just crammed into a project box?