Relay Delay

You can purchase time delay relays that allow you to set up timing sequences based upon your trip conditions.

I used these about forty years ago to manage the power up sequence for test equipment.

DAB

Hi Nick, there are commercial products available that do this. they are called Delay on Make Relays. I have worked with them in the past. Some come with DIP switches that can be set to program the number of seconds of delay between the powering of the circuit and when the relay closes and actually turns it on. There is a small preliminary current that has to pass through the module to power its internal electronics while it times out and closes the main sircuit allowing the circuit to come up to load amperage.

http://www.newark.com/artisan-controls/438usas/solid-state-timer-1024sec-288vac/dp/86K9984

This unit will work on 19V all the way to 288V AC or DC.

John

Heavens Tbilisi!  'A while!'  I will presume a coupla seconds like you are shorting out the current limiter on a bypass cap.  'Turns on' is also problematic if you don't specify after being off for at least so-and-so period.  I will further presume your excitation is DC.  You hook up a RC string across the supply.  The tap goes to one of the inputs of a voltage (hate that word!) comparator.  The other input is a reference, like a backwards Zener (or coupla LEDs, even) with a ballast R, maybe, say 2/3s Vcc.  Timing cap charges, changing potential at the tap, comparator triggers Q which fires relay.  Comparator has provisioning to avoid the jits, such as Schmidt action.  Alternatively, Norton comparator with input resistors.

If you need more time, one option is a capacitance multiplier circuit.

Yes, sorry for saying 'A While', I did mean just a few seconds. Its for speaker protection circuit put in my amp. Because of that loud THUMP sound I get when the power goes directly on.

If you dont want to buy any new relays you could use a 555 timer to trigger the the relay their is a great calculator here 555 timer under section 3 and the rest of the page is full of every kind of 555 circuit you could need. i hope that helps.

Hi Nick, For the purpose of delaying the connection of speakers to the amplifier I would forget about the "delay on make" modules that I previously recommended and instead use a 555 timer connected to a mechanical relay as Don and others have advised. The delay on make module can delay the closing for up to 17 minutes but if all you need is a couple seconds the 555 timer and appropriate RC network will be best. Also the mechanical relay will give you a hard connection of the speaker line while the delay on make module always has a voltage drop accross its connection.

John

There are a lot of topological possibilities for a circuit that creates a delay.  Let me abstract this discussion a little bit from your application.  You can extend the delay period for just about any setup that uses a timing capacitor which has one side attached to the supply with a capacitance multiplier circuit, which is just a few Rs and an op-amp.  You can learn something about e- by building it and seeing how it works.  100x extension on time is easily achievable this way.

Without such tricks and with ordinary components, it is hard to fab delay circuits that take longer than c. 10 s.

Alternately, you could use a counter (w F/F and osc) to achieve multiples of your intrinsic delay.

Commodity comparators and 555s cost about the same, though you get a 3R string and a F/F on the 555.  Even if you use a 555 you should be careful to 'think inside the chip' to understand its functions.  You can always make a F/F out of a pair of gates if that is convenient.