serial port relay help - new problem

**brianhj** · 08-23-2009, 07:29 PM

i'm getting 11.88v from my serial port DTR pin... how can i switch a relay using this? layman's terms please

my knowledge of electronics is fairly limited. i've searched the web and the info i find is either over my head or doesn't pertain to my particular application.

**brianhj** · 08-24-2009, 08:59 PM

anyone?

**mentor** · 08-24-2009, 09:32 PM

I used a Pac-TR4 which can sense low voltages and give a steady 12 volt output @ 2 amps which was more than sufficient to run my amps. These are not very expensive on ebay and mines been working for almost a year with no issues.

So the output (DTR) from my serial port is an input to the Pac TR4. Once the DTR is raised I can use TR4's output which is 12 volts.

**brianhj** · 08-24-2009, 09:57 PM

who'd a thunk it'd be that simple!

thank you!!!! just what i was looking for.

**brianhj** · 08-26-2009, 06:55 PM

when windows is booting, serial port DTR is raised several times causing my relay to go crazy... switch on and off on and off. I'm assuming it's windows initializing the serial port.

What can i do??? grrrrrrrrr

**malcom2073** · 08-26-2009, 08:22 PM

brianhj: You can put in a timer on another relay, which disconnects the line for 30 seconds (or however long) until your computer boots... otherwise there isnt much way around that issue. Search the forums, there has been discussion about this before.

**brianhj** · 08-26-2009, 09:12 PM

that would completely defeat the purpose of having the serial port relay in the first place. did you even read the thread?

**Curiosity** · 08-26-2009, 10:19 PM

Open Regedit. Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Servic es\SerMouse, and change the value "Start" from 3 to 4.

**Superduck** · 08-26-2009, 10:23 PM

How long are the pulses? I'd imagine some sort of a debounce circuit would possibly work. Perhaps something like this would do the job? If the pulses are longer, you might need to use a bigger cap? Someone with more electronics knowledge might be able to tell you if this will work for sure, and what value you'd need for the cap. I'm sure there's several other ways to make that work anyway. Perhaps just adding a single cap in line? /shrug

Good luck,

Kris