Magnetic Monopoles Discovered! (Featherweight Magnetic Switch issues)

[CCotner]

I was helping some friends with a F-F minimum diameter two-stage flight this weekend. It didn't work (sustainer failed to ignite) for operator~error induced reasons, and other than the first stage coming in ballistic after kicking my 29/40-120 case instead of a parachute but not damaging either case or rocket, it went well.

While setting it up, however, we ran into an odd behavior of the magnetic switch. Jammed together in a 29mm coupler along with the raven and battery, the switch was absurdly close to the raven itself. Wile blue-tapped together outside the rocket, we practiced turning the assembly on and off with the magnet; then we took the tape off, and went to load it into the rocket. The funny thing was, when we put the raven and the mag switch next to eachother to start stuffing, the magnetic switch turned on. This happened three different times in a row, and then stopped happening, and hasn't happened since.

Other than the ultra-capacitor having captured, if temporarily, an elusive magnetic monopole, returning true symmetry to maxwell's equations for electromagnetism and making me a shoe-in for the nobel prize 50 years from now, are there any plausible explanations for this? How does Adrian deal with this problem in the equally-ludicrously-tight confines of the 29 and 24mm Av-Bays?

 

[troj]

Is it possible something else, such as possible the case of a 9V battery, got magnetized?

-Kevin

 

[WillMarchant]

Or did you short the switch board to the altimeter in the process of cramming things in? If you left masking tape on the exposed board faces and edges then I wouldn't expect a problem. Unless you tore the tape on a sharp edge during stuffing.

 

[CCotner]

There weren't any other metal objects, other than objects on the board of the raven, inside the bay.
The switch acted like it had been engaged in the normal mode; both the raven lights came on, as did the light on the switch. We did have shorting troubles, and one of the students involved destroyed one of my Li-Po batteries shortly before that by shorting the ends of the screw switch. It didn't seem to affect the switch, though.

And yes, I am aware of all of the things wrong with this situation, and no, I was not comfortable with it, but it wasn't my rocket, and I/they were all under pressure to perform yesterday, but I think I did everything I could to to keep them/spectators/myself safe without just asking them to not launch.

 

[CarVac]

And had it ignited the top stage (we think the igniter wasn't all the way up to the pellet) it would have gone up perfectly fine, and even though it didn't the Raven properly ejected at apogee..

I was in the same room while the problem occurred, and couldn't think of any reason other than something on the Raven becoming magnetized.

 

[G_T]

Along with the metal/conduction/short which you've discounted, is there carbon fiber in there to short against? Carbon fiber is conductive. Some paints are probably conductive as well.

Gerald

 

[CarVac]

Nope. Blue tube.

 

[Reinhard]

The beeper on the Raven might be the cause. There are different types, either piezo based or magnetic ones. The latter could have an effect on the magnetic switch. I don't know which type Adrian is using.

Reinhard

 

[Adrian A]

I was helping some friends with a F-F minimum diameter two-stage flight this weekend. It didn't work (sustainer failed to ignite) for operator~error induced reasons, and other than the first stage coming in ballistic after kicking my 29/40-120 case instead of a parachute but not damaging either case or rocket, it went well.

While setting it up, however, we ran into an odd behavior of the magnetic switch. Jammed together in a 29mm coupler along with the raven and battery, the switch was absurdly close to the raven itself. Wile blue-tapped together outside the rocket, we practiced turning the assembly on and off with the magnet; then we took the tape off, and went to load it into the rocket. The funny thing was, when we put the raven and the mag switch next to eachother to start stuffing, the magnetic switch turned on. This happened three different times in a row, and then stopped happening, and hasn't happened since.

Other than the ultra-capacitor having captured, if temporarily, an elusive magnetic monopole, returning true symmetry to maxwell's equations for electromagnetism and making me a shoe-in for the nobel prize 50 years from now, are there any plausible explanations for this? How does Adrian deal with this problem in the equally-ludicrously-tight confines of the 29 and 24mm Av-Bays?

Was the Raven powered on when it was stuffed in? If so, the beeper could be the cause since it does have a magnetic coil. In the Featherweight av-bays, the magnetic sensor is past the terminal block and so it's far enough away from the beeper not to be a problem. If it was not powered on, you probably have something magnetized. Did you have any steel components in the av-bay? A lot of screwdrivers are intentionally or unintentionally magnetized, so if there was one in the vicinity, that could be an issue.

 

[CarVac]

The avionics bay was just a Blur Tube coupler with the Raven and switch stuffed in it, with wooden bulkheads and retained in the rocket with plastic rivets. The Raven was off initially, and when squeezed against the switch it powered on.

At one point there were little screws holding the wires to the switch, but I don't remember if they were stainless or regular steel and whether the problem was exhibited before or after they were removed and replaced with soldered connections.

 

[CCotner]

Was the Raven powered on when it was stuffed in?...Did you have any steel components in the av-bay?

Nope and only an eyebolt that was .25" away in-plane of the mag switch breakout board, where it shouldn't have effected the switch.

you probably have something magnetized.

Yeah, I figured. I was wondering what kind of thing, possibly on the raven, could be magnetized. Maybe the usb plug?

 

[CCotner]

The avionics bay was just a Blur Tube coupler with the Raven and switch stuffed in it, with wooden bulkheads and retained in the rocket with plastic rivets. The Raven was off initially, and when squeezed against the switch it powered on.

At one point there were little screws holding the wires to the switch, but I don't remember if they were stainless or regular steel and whether the problem was exhibited before or after they were removed and replaced with soldered connections.

They were stainless, and in any case, since they were fixed relative to the sensor, so I don't think they could be the cause.

 

[CarVac]

If they were paramagnetic slightly (just a little) perhaps it could have acted as a conduit for magnetic flux from something on the Raven that was magnetized.

 

[Nerull]

If power is removed, and then reapplied, the magnetic switch defaults to on. Is it possible you lost battery power for a moment?

 

[CCotner]

That is probably what happened. Thanks for the insight! Where did you learn that?

If power is removed, and then reapplied, the magnetic switch defaults to on. Is it possible you lost battery power for a moment?

 

[Nerull]

That is probably what happened. Thanks for the insight! Where did you learn that?

Playing with the magnetic switch in my av-bay when I first got it. I'm using the separate switch with a stratologger, but I imagine the versions in the power perch and raven av-bays work much the same. I would guess this is a safety feature - a transient power loss in flight will not turn off the altimeter. Backup power capacitors won't do much good if the power switch turns itself off.

The switch does seem to remember its on/off state on very short power losses. I have not experimented to see how long power has to be removed for it to reset back to the on state.

 

[Adrian A]

Playing with the magnetic switch in my av-bay when I first got it. I'm using the separate switch with a stratologger, but I imagine the versions in the power perch and raven av-bays work much the same. I would guess this is a safety feature - a transient power loss in flight will not turn off the altimeter. Backup power capacitors won't do much good if the power switch turns itself off.

The switch does seem to remember its on/off state on very short power losses. I have not experimented to see how long power has to be removed for it to reset back to the on state.

Good call. I think you solved it.

I designed the magnetic switch with a large enough capacitor on the output of its linear regulator so that the altimeter can short the battery for a few seconds and the switch will remember its state. The av-bay switches don't need a linear regulator so I have a diode there instead.

The switch state at turn-on is governed by the power-on state of a discrete flip-flop, and it can go either way. In my experience, about 90% of the magnetic switches default to on when the battery is applied. But once the battery is connected, it will keep its last commanded state for a few seconds even if the battery is shorted out briefly.