Hacking into the FIrebird XL

[stevem1928]

Is it possible to use the hidden module pins in the Firebird Xl for a non proportional servo activated by pulling down on the throttle stick? The Firebird XL has a 4 pin header hidden on the inside. It is suppose to only be available on the Fighterbird. It is used for the add-on Sonic Combat Module (SCM). The firing mechanism is activated by pulling back on the throttle.

The header pins have been identified as #1 Ground, #2 Firing, #3 weapon hit (this would cut the motor), #4 +4.8v.

The pins could be adapted to match the configuration of the servo: ground, +4.8v, signal. I suspect that pulling back on the throttle would activate a servo in some way. All I am looking for is a way to rig a parachute drop or camera activation. It does not need to be proportional. I have a lot of other planes capable of doing this. But, I have a location near my parents home which is near an R/C field. I would like something to fly at this location that does not interfer with 72mhz. The Firebird is on 27mhz.

What risk do I run when connecting a servo to the 3 pins? I have some old servos which would not be a big loss if I ruined them.

[Mr.RC-CAM]

What risk do I run when connecting a servo to the 3 pins? The only risk I can imagine is that the servo may move to its mechanical limit and damage a gear.

Although I do not expect the servo to operate normally, it may be worth trying. The five minute test will at least tell you something.

RC-CAM

[stevem1928]

I went ahead with the test. Used a 9 g servo. When I got everything plugged in, there was a lot of servo chatter. When I pulled back on the throttle, the servo moved. It only moved about 1/4 of its normal range. At the same time, the tail servo made very small movements back and forth. When I moved the tail surfaces, the add-on servo moved a bit.

I will try a ferrite ring and try again. Do I wrap the servo wire around the ring as many times as possible?

If I can eliminate the interference, this could make a cheap turnkey camera plane for $110.

[MattLarson29]

They have a drop module, you could probably easily adapt it.

Matt

[Mr.RC-CAM]

Are you sure the servo isn't stalling?

I suggest you try using Wild Moose's shutter board or this design: http://www.uoguelph.ca/~antoon/gadgets/rc-sw.htm

These designs have a pot on them to select the pulse width threshold. With luck, they will work without too much fussing.

RC-CAM

[stevem1928]

How does a servo stall?

[Mr.RC-CAM]

How does a servo stall?In this example, if the pulse widths of the X-Port's servo signal are outside the 1.0mS to 2.0mS range, then your foreign servo can be driven until the internal gears hit a stop mechanism. Once stalled, the motor will continue to draw current, but at a very dangerous rate. Yup, this is a bad thing.

If you find that the servo moves to the end-of-travel while you move the sticks then it is stalling. This would be a serious burden on the Rx's BEC, so it is best to watch for this fault.

I only mention this because I do not think the signal that comes out of the X-Port follows the standard R/C convention. This is just a hunch that is based on what I saw with the Sonic Combat Module's internal circuitry. Precisely derived pulses are not required to trigger that nifty device, so they may have cheated a bit in the X-Port's design. Only an o-scope would tell us for sure.

RC-CAM

[stevem1928]

QUOTE NPM
Sonic cannon on an Aerobird
I purchased the parts required to make the original circuit adapting the shooter as listed in the article. When I took the circuit board out of my aerobird and compared it to the circuit board in the Fighterbird they looked fairly similar except for the different servo set up. There is a spot on the Aerobird board where the 4 pin connector to plug in the shooter would be if it was a Fighterbird. I am wondering if I can just put the connector on the Aerobird board and connect the sonic shooter straight up with out the additional circuit? Does anybody know about this?
END QUOTE


The above quote was taken from another thread. http://www.rcgroups.com/forums/showthread.php?s=&threadid=129958

I have 2 FIrebird XL's. I bought both used for $30 & $50. One of them must be older than the other one. One of them has the 4 pin header connected and ready to go as a Fighterbird. The other (must be older) only has 4 holes where the 4 pin header would go. The plane with the 4 pin header works perfect with the sonic comat module (SCM). I tried to put a makeshift 4 pin header on the other one. I can't seem to get it right. It has not worked for me yet. But, I am sure it will work as soon as I buy a 4 pin header.

This may not work on the Aerobird since it is already using a third channel.

[npm]

Thanks for the input stevem1928. I suppose it would be best to hook a battery to the fighterbird circuit and measure with a volt meter what is happening at the various pins and then doing the same thing with the aerobird circuit. If it is this simple that would be fantastic.