Windows Service that raises DTR on powerup

**awh4992** · 01-09-2004, 08:47 AM

[QUOTE=GingerPrince]You could also use it to power a relay to turn your neons on/off

[/QUOTE

that would hafta be a pretty small relay as the serial port DTR and RTS lines only supply ~10mA, which is barely enough to power a chip or 2, let alone an electromagnet in the relay. a better way would be to just use a transistor that can switch the amount of current ur neons use. the transistor only sucks nano to microamps through its base, so it's suited better for driving loads as opposed to sucking current from an output on the serial port chip. you would be using an npn transistor since the DTR pin is negative until the OS tells the serial chip to bring it to about +8 or +9v. a relatively simple circuit to build, providing you can get your hands on a transistor that won't blow up when u have ur neons connected directly to it.

**numberone** · 01-09-2004, 06:11 PM

You should find schematics on the web, if not - get back to me and i'll post one..

How do you connect your amp to the serial port?
My amp needs 12v to the remote input. Can I get this from the port?

**crosseye** · 01-09-2004, 08:47 PM

Originally Posted by awh4992

that would hafta be a pretty small relay as the serial port DTR and RTS lines only supply ~10mA, which is barely enough to power a chip or 2, let alone an electromagnet in the relay.

You can buffer the DTS line (or place two inverters back to back). The output of your buffer should then have enough current to power the relay.

**Twizted** · 01-09-2004, 09:12 PM

Easy thing to do would prolly be use a general purpose transistor MPS2222 (prolly need something larger that can handel around an amp or two) for example to connect the 12v to a 12V Relay to turn on the neons... I would say you would need to so the same for the amplifier remote switch... I will have to look into this myself as I will need it.. If anyone can elaborate on my idea or share there design or idea please do

Here is a link to the
.NET Framework 1.1 Redistributable Package that Microsoft offers...

**Da_Teach** · 01-11-2004, 08:06 AM

After a bit of testing, I found out that directly wiring the DTR to the AMP works, but sometimes fails... So I'll have to put 'something' between the AMP and the serial port... So give easy idea's

**burnout.no** · 01-12-2004, 03:53 AM

Well, I also wired the DTR directly to my AMP, works ok!

Da_Teach; Maybe it's just xp that screws it up?

**Twizted** · 01-12-2004, 11:52 AM

An easy solution would be useing a simple switching transistor... I am thinking something such as a 2N2222 NPN General Purpose Tran. would work..
It can handel around 60v on the base (DTR output) which is well over enough and can put out as much as 40v on the emitter side (To amplifier)... The only possible problem I see could be it can only handel up to 800mA of current at the collector (12v input to turn on amp)
I am not sure if that would be enough to turn on the amp or if the transistor could even handel being hooked into a car electrical system? Anyone have any ideas on this... I can test is later if need be...

Simple diagram of this application if it would work is

*note* the transistor is quiet small (excluding the sire leads the actual chip is smaller than your pinkie nail) the size on picture is just for referance...*

**Edit**
As this is a simple cheap way of doing this I would suggest the use of an opto-isolator in this case for added protection of the PC... If this would work and someone would confirm it I will try it in my Van (normal system) just to test the therory...

**Da_Teach** · 01-12-2004, 01:16 PM

Well the problem I ran into was that the amp turned off half-way during the journey... I first thought I blew up my serial port, but I think its because my serial port doesnt output enough voltage ... It starts off at 10v but after a while drops to 7v, which probably made my amp shut down...

**Twizted** · 01-12-2004, 01:36 PM

Probably so... The base on the Transistor above will activate at very low voltage all the way up to 60v.... I have used them on small projects that only output 5v and less... and up to 12v....