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ryanhettenbach

Rocket assist project

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Hello all! I'm a new member and an owner of an Aerobird Commander with the ever popular X-port. My friends and I are interested in doing a rocket assist either for launching or maybe some mid-flight "fun". So this leads to my next question. How does the X-port work? I broke out the multimeter last night and this pic.

xport1.jpg

First, I verified that the outermost pins provide a constand voltage of 7.2V. The 7.2V should be enough (of course I'll use slightly heavier gauge wire) to fire off the ignitor. But I can't seem to figure out how the 2 innermost pins operate. Are they supposed to put out a voltage? The most i could get out of either was only 0.25V without the button on the controller pressed and 0.8V with the button pressed. I was mislead by another message board that said the 2 innermost pins are +5V and -5V respectively. Since I assumed this person was correct, I went to radioshack and purchased this

RADIOSHACK 5V RELAY

I was really hoping to use a relay to fire the rocket ignitor. Is this a possibility and how should I wire it up?

Thanks in advance and any help you guys can give is greatly appreciated.

Edited by ryanhettenbach

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It's not quite that simple. Pin 3 is the X-Port signal, which is essentially the receiver's raw demodulated FM signal. It contains data to more than just the xport specific events, so it cannot just connect to a relay. Your circuit will need some electronic brains to handle that. The easiest solution is to buy the HobbyZone bomb drop module and hack it to control your relay. Some folks have done this to control camera shutters, so try Googling for more info.

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Thanks!

Is there anywhere I can get the schematics for the Drop Module internals and build the curcuit myself? I'd really hate to waste a perfectly good drop module!

Edited by ryanhettenbach

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Their schematics are not available. Even if they were, you would still need their proprietary software that is used in the bomb drop's microcontroller. Getting that would probably be like winning the lottery.

If you use sane construction techniques, the bomb drop unit could be restored back to its original condition when you needed to do that. It is all up to you.

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The bomb drop module uses an electromagnet to control the bomb release. As the electromagnet is always on unless you hit the release switch, it will use a high(er) current when it is holding the bomb compared to when it is releasing it. So find something that will A) check and compare current levels or that will B) check and compare magnetic field strengths. Something that wil help with solution B is called a Hall Effect Sensor - it measures the magnetic field strength.

Anyway I hope this helps some1 :).

Regards, Pyrotechnician.

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Any luck so far, ryanhettenbach?

I've been planning to open up a bomb-drop module to see if it supplies enough current to its electromagnet to actuate a micro-sized relay instead (thinking RS #275-240 5v spdt relay $4.49). If it does, the normally-closed contacts on the relay (which will be open until the x-port is triggered) can be used to switch current from the plane battery to a model rocket ignitor. I'm thinking in-flight launch mechanism for some wing-mounted bottle rockets here - air-to-air missile dogfights, anyone?

There's probably a very simple transistor switch circuit (darlington, maybe) that could replace the relay approach. Where's my dvm gone to...

I'll try to capture some airborne video if I get this working, assuming the bottle rockets don't set the wings on fire, that is. Of course, that would make for even more compelling viewing, eh?

Keep up the good work, Mr.RC-Cam - these forums are a fascinating source of information and expertise about this rapidly-evolving hobby.

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