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- Jun 21, 2012
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Indeed there is a huge difference between zero and 0.3 seconds... in fact the difference is 0.3 seconds, roughly about the time it takes for the average electromagnetically actuated armature to transfer the contacts attached to it from "open" to "closed" or vice-versa.
There are much faster relays than the Hella thingy you are stuck with. Reed relays come to mind. Some reed relays can open or close in a few milliseconds, well within your timing constraints. Some of the things we would need to know to design and build an appropriate circuit are what kind of load the contacts are expected to switch, what voltage is presented to that load, and what is the peak as well as the steady-state current in the solenoid.
A solenoid can be constructed for either AC or DC operation, but in either case it has inductance which will slow it down when it is first energized, unless other measures are taken to compensate for the inductance, such as briefly increasing the voltage supplied to the solenoid beyond its rated voltage. Even if only the rated voltage is applied, not all solenoids are designed to survive continuous actuation. You haven't stated yet how you plan to turn the solenoid off after the button is released and the time delay occurs, at the end of which time delay the solenoid is energized. Or have I got this wrong? Perhaps the solenoid is energized when the button is pressed and is then de-energized after a time delay when the button is released? Which way is it?
There is also the question of what happens when the solenoid is de-energized and its magnetic field collapses. That never happens instantaneously and it is always accompanied by a so-called "back EMF" or back electromotive force, an ancient term for voltage. In simple terms, trying to reduced the magnetic field in a solenoid will result in the generation of voltage by the solenoid that will try to maintain the current that produced the original magnetic field. This voltage can be quite large, much larger than the original energizing voltage, depending on how fast you try to turn the original current off. It can cause arcing at relay contacts that will either destroy the contacts (eventually) or cause them to weld together. There are many solutions to the problem, but all involve dissipating the energy stored in the magnetic field of the solenoid, and all result in a slower de-actuation of the solenoid.
It is for the above reasons that it is necessary to know what you trying to do with the solenoid as well as the electrical characteristics of the solenoid. A part number and manufacturer of the solenoid would be helpful, as well as knowledge of the type of mechanical load the solenoid will be driving. For example, is the solenoid armature or plunger operating against a spring? What distance does it move? How much force is it expected to produce? What is the mass of the moving parts? How fast are the moving parts expected to move?
I am sorry if all this sounds overcomplicated compared to your original request, but you are venturing into an area called mechatronics, the integration of mechanical engineering with electrical engineering. In the past, MEs and EEs got by with minimal communication, and their designs suffered for it. Today most engineers must embrace both disciplines and, depending on the application, even more esoteric subjects.
Good luck finding someone who will build what you need based on the sketchy information you have provided so far. If I were that person I would demand a "best effort" time-and-materials contract with a fixed fee and no guarantee that it would work for your purposes. The only entities I know of who agree to such terms are agencies of the U.S. Government... your and my tax dollars at work.
The Hella relay actuates immediately when power is applied to it via your push button. When you release the button, the relay de-actuates after a time delay. Even if the timing were what you want, I don't see how this relay de-actuating will accomplish your goal of energizing the solenoid after a time delay. The relay is de-energized BEFORE you push the button and it is de-energized (with a time delay) AFTER you release the button. How is the solenoid not actuated under BOTH of these conditions? Or does pressing the button actuate the relay AND the solenoid at the same time, with the solenoid de-actuating after a time delay when the button is released? A wiring diagram would help.
