"and the solenoid could be pulsed (via a MOSFET) "

Oh, I love it when you talk techie to me. Of course, I don't have a clue as to what that means. My understanding is that the solenoid needs but one "pulse" to pull it open/back and release the door/gate.

Honestly, I do not understand the pulse thing.

A pulse is nothing more than applying power for a short period of time. The solenoid will have a mimimum actuation time in order to operate. In addition, it will take some time (short, but still some time) for the gate to be pulled by the spring and start moving. Therefore, the "pulse" of power to the solenoid must be at least as long as those two actions take. In this application, the easy way out is to make the pulse a second or two long, because there is no penalty for a pulse that is too long.

I don't know what you have in mind for the latch mechanism, and I know you said you could handle it, but I hope you aren't planning to have the plunger of the solenoid act as a striker that hits a latch when the gate shuts. I think that would put too much lateral pressure on the solenoid, and unless it's bigger than I imagine, it wouldn't hold up well. I suppose that you also know that solenoids are made to actuate by electromagnetics, but they usually rely on a spring mechanism to "un actuate," and the spring usually doesn't have as much power as the actuation. Just something to keep in mind as you design the latch.

BTW, if I'm providing more info than you want or need, just say so, and I'll lighten up. I am especially interested in this project because I plan to build a chicken coop and run next spring, and plan on having some of the functions automated in much the same way as your dog pen.

 

"Solenoids typically do not have much "throw", mabye 3/4" effective at best, and no holding power"

I can get by with a spring-loaded bolt that retracts less than 1/4" and, it does not need to "hold" as it is at rest when holding the latch mechanism. When powered, it retracts and releases the latch mechanism.

All need is the electronic circuit to power the solenoid on long enough for the bolt (by which I mean the part that is retracted into the coil portion of the device).

Think of an ordinary bedroom door. The door latch bolt is angled on the face toward the jamb so that, when you shut the door, the bolt retracts into the door unitil it clears the strike lip when it enters the hole in the strike. When you open the door by turning the handle (think solenoid activation) the bolt is retracted into the door and clear of the strike and you can pull or push the door open. Now, if the door had spring hinges that pulled the door "open," just turning the door knob and retracting the bolt would allow the door to swing open.

Hope that makes it clear.

 

Please see my recent post re: Bedroom Door.

Yes, I plan to do as you surmised and think, because of the light weight door, that I can get away with it. The spring that returns the solenoid bolt to rest position should not prove an issue unless it is too strong and (with the lateral resistance mentioned) can't be overcome by the electromagnetic coil of the solenoid.

Need sleep.

 

"A pulse is nothing more than applying power for a short period of time"

OK, thought it was something I needed to build into the circuit

 

"A pulse is nothing more than applying power for a short period of time"

OK, thought it was something I needed to build into the circuit

No, that's "Patience"

 

The circuit I drew has such a pulse. You could replace a resistor for a pot to vary the time.

 

Q1 is a specialized part called a logic level MOSFET. Mouser Electronics[/url] carries these parts. C8 needs to be as large as you can make it. The value named is for convenience. CR1 and CR2 should be large current Schottky diodes. I have no clue The battery voltage is somewhat dependent on which solenoid you are planning on using. The transistor is rated for 16A, so it should be good. You must use CMOS 555s here, else your battery will run down very very quickly. A 7555 is a version of a CMOS 555, Radio Shack sells a version called a TLC555.

Not sure of what that typo should have said. I excerpted your comments to define the recommended circuit by removing the options indicated as I am to much a novice to replace the two 555's with one 7556, for instance.

I assume I can search for Scottky's diodes - but would Radio Shack by as likely a source or are they rather specialized components?

I went to Mouser, but it appears that they want to sell me dozens or more at a time. Because I am on dial-up, searching about on some of the sites loaded with images can be a real chore.

You show 6VDC as the power source. Is this the max the circuit will take as drawn? Middle of the range? That is could I go to nine volts without having to change components in the circuit provided? Or should I come back when I've found a solenoid and ask then?

Charles

 

6VDC was what you originally stated as the power supply voltage, or at least that is my impression. You need to match your power supply to the solenoid (or whatever you use). It dictates everything else.

The rest of the components are not too critical as to the voltage, they work over a wide rance, except the logic MOSFETs. MOSFETS are not too critical either, you just need to match them to your application.

You can use 1N4001 diodes, which are available everywhere. It is up to you, but I would try to use other than Radio Shack, they have a significant markup compared to other vendors. Schottky are much better for many applications, but it is not critical.

I trying to link a vendor to the part, which is the typo you are talking about.