RFID Response time

Hi there.

I am developing an Arduino based control system for a glider launching system.

I'm about 99.9% complete and I only need to deal with the line recovery phase.

Basically, once the glider has done with the towing session, there is up to 3000ft of tow line to be reeled back onto the winch drum.

I'm looking for a way of detecting when the end of the line is near. (The line has a drogue on it to offer some resitance during the line recovery)

I was thinking of using an RFID capsule embedded in the line. As the RFID capsule passes the RFID reader I can detect it and shut the winch down.

Question is this: What is the response time for an RFID reader as a capsule is placed near it. It has to be quick and I suspect it will be ouside the 200ms range I need

Nigel

enveetee: Hi there.

I am developing an Arduino based control system for a glider launching system.

I'm about 99.9% complete and I only need to deal with the line recovery phase.

Basically, once the glider has done with the towing session, there is up to 3000ft of tow line to be reeled back onto the winch drum.

I'm looking for a way of detecting when the end of the line is near. (The line has a drogue on it to offer some resitance during the line recovery)

I was thinking of using an RFID capsule embedded in the line. As the RFID capsule passes the RFID reader I can detect it and shut the winch down.

Question is this: What is the response time for an RFID reader as a capsule is placed near it. It has to be quick and I suspect it will be ouside the 200ms range I need

Nigel

If response time is a problem, you could just mount the RFID reader farther away from the spool, on an arm or something. However, i don't think the RFID reader will have time to register that the tag is near it, if its moving that fast.

We have a hose reel that uses a styrofoam ball about 16" from the end of the hose, and a limit switch to shut the thing down. You could have a spring mechanism in the styrofoam that gives a little when it hits the switch, or you could just let the styrofoam slide on the string, and have a sensitive limit switch.

I assume weight is an issue here, so the styrofoam may be too heavy. What is the line made out of? An optical sensor may work if you paint the last foot of line bright red or something.

Basically a 125KHz RFID takes about 40mS to read. Depending on the way the software is written it could take up to twice that time to get a reading. But 80mS is still fast enough for you.

Why not put a small conductive section close to the end of the line? Or a magnet? Both would be much easier to detect than a rfid tag.

Wizdum, GM and UK, thanks for the input good ideas...