Input LED Status to Serial Port

zzzBrett · 03-12-2008, 03:56 PM

I have a radar detector that flashes LEDs when it senses different types of radar. I would like to, somehow, wire the radar detector to my computer with the serial port, and have the radar status display on my computer screen. First, I'm attempting to deal with the hardware side:

I took apart the radar, and used a multimeter testing the LED solder points with ground, and found that when all of the LEDs are off, each solder point reads about 4.4v, but when one of them flashes, it drops down to about 3.6v, then back to 4.4v when it turns off.

I was thinking I could use a relay to close a connection whenever the LED flashes on, but not sure how to go about doing this, or how to find a relay that is for the specified voltages.

Please help me with some ideas as to how I would use this as an input for my computer.

Thanks,
Brett

NiSlo · 03-13-2008, 01:58 AM

Might I suggest the Fusion Brain which was developed by a couple of blokes on these boards. You can find the forum here and they have a website you can purchase them from here.

Sounds like it would do exactly what you want and save you alot of mucking around.

zzzBrett · 03-13-2008, 02:11 PM

Thanks for the suggestion, but I'd rather make something myself. Half the fun for me is the "mucking around". Someone suggested to me using an optocoupler. I'm not sure how to use one of these, but from what I understand its an optical relay. I assume i'd have to find one with the same voltage as the LED on the radar detector have?

Thanks,
Brett

zzzBrett · 03-18-2008, 10:41 PM

I think i've found a way to use an optocoupler in combination with the radar, then interface it with USB! I'll be posting back with more updates.