Thread: delay circuit

I use the DTR line from a serial port for remote amp turn-on. The DTR line is low at boot, then I set it high in software (not sure what's the easiest way to do this in Windows, though). If you do this, use a small fuse on the line just in case...

Can you please describe this method with more details please ? (COM DTR...)

Yes, PLEASE... this would be VERY nice.

(I'm getting quite sick of forgetting to shut my amps off before I boot... sounds like someone fires a gun in the back seat when the computer boots )

Hmmm, let's see. As far as hardware is concerned, the DTR line is pin 4 on the DB-9 connector (pin 20 on DB-25). So you just run a wire from this pin to the remote-on terminal of the amp, but put a small fuse (250mA or so) on the computer side of the wire, just to be safe -- otherwise a short could blow your serial port.

The serial port will provide about +12V on the pin when some program opens the serial port and sets the DTR line "high". This will tell your amp to turn itself on. When the program sets the DTR line "low", the pin drops to -12V and turns the amp off (you might want to add a diode to the wire to make -12V appear as 0V. I did not do this, and it works fine anyway.)

Now, as far as software is concerned, fortunately I really have no idea how you can manipulate DTR under Windows (see my sig...) Check with a multimeter: DTR might be set high at boot time already. Can anyone else here comment on this?

Good luck.

Setting that to high could easily be done with a C++ .exe that you could put in your autoexec!

I could write it up for you real quick-like on monday, but I'm in Houston right now on my laptop, and don't have a compiler with me

I'm thinking of make simple delay to amp's signal-pin or whatewer(low A start like relay)

like this

Code:

  
                     Resistor

computer ps 12V >--|===|----+--< amp sign.
                        |
                        = Capasitor
                        |
                        +gnd


When I turn comp on The resistor will slowly rise the C voltage to 12 V and amp will go on!

But how about disabling the shutdown *bumb*???

The whole point of using DTR is to be able to turn the amp on _AFTER_ the PC is on (delay-on), and to turn it off _BEFORE_ the PC is off (pre-off). Using a +12V line from the power supply doesn't help at all, you'll still get the thumps. And while you can do a simple delay-on circuit like embedded suggested, there's no way you can do anything similar for pre-off -- a simple circuit, not being able to see the future, can't tell when your PC is about to turn itself off. But software can.

I'm pretty sure I can handle writing a serial port app to handle the DTR. I might even be able to get it to work for the 2000 guys. I'll have to try the wiring trick when I get home, and whip out my compiler for the software.

I'll report back if I have any success, and share the software if it's worth having.

-M