New and improved Featherweight magnetic switch

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Adrian A

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New Featherweight magnetic switches just arrived.
IMG-0996.jpg
They have the same form factor and mounting holes as the previous version, but the new electronics perform significantly better than previous versions:
  • Longer range. A small (1/4" diameter, 3/4' long) rare-Earth magnet now activates the switch from 1.75", up from about 1." This gives more flexibility for locating the switch within the av-bay.

    IMG-0997.jpg

  • The new magnetic sensor turns on with one magnet orientation and then to turn it off, flip the magnet 180 degrees. This makes it easier to have multiple magnetically-activated switches in an av-bay, because if you're trying to turn everything on, you won't also accidentally turn one one of the devices off when the magnet passes by.
  • Lower standby current. The switch draws about 13 micro Amps when it's off. This is low enough to prep your rocket and button it up whenever you want to before the launch. For example, let's say you use it to connect a 400 mAhr tracker battery to a Featherweight tracker the week before a launch. But then launch gets rained out and your rocket is still prepped and waiting for the launch 1 month later. In 30 days, the switch will drain the battery by only 9.4 mAhrs out of 400.
  • The new switch's default state is off. When the battery is connected to the switch, the switch output is off until the battery turns it on.
  • High current capacity: The output FET is rated for 20 V and 24 Amps.
  • The switch remembers the last state for about 2 seconds if power is temporarily interrupted.
 
Very nice Adrian !

I take it from context that I can test the Switch with only In and Ground connected to a battery ( no need for output ) ?

If so, that's good to know for testing.

The new features are great !

I suppose that the new 'default off' state explains why the Blue Raven usually boots in my Power Perch AV-Bay when I plug in the Battery ?

Thanks for the update.

-- kjh

p.s. I'll have to redesign my 'magic mag wand' so I can flip the magnet in the holder :)
 
Very nice Adrian !

I take it from context that I can test the Switch with only In and Ground connected to a battery ( no need for output ) ?

If so, that's good to know for testing.

The new features are great !

I suppose that the new 'default off' state explains why the Blue Raven usually boots in my Power Perch AV-Bay when I plug in the Battery ?

Thanks for the update.

-- kjh

p.s. I'll have to redesign my 'magic mag wand' so I can flip the magnet in the holder :)
Yes, both are correct.

-Adrian
 
New Featherweight magnetic switches just arrived.
View attachment 583239
They have the same form factor and mounting holes as the previous version, but the new electronics perform significantly better than previous versions:
  • Longer range. A small (1/4" diameter, 3/4' long) rare-Earth magnet now activates the switch from 1.75", up from about 1." This gives more flexibility for locating the switch within the av-bay.

    View attachment 583240

  • The new magnetic sensor turns on with one magnet orientation and then to turn it off, flip the magnet 180 degrees. This makes it easier to have multiple magnetically-activated switches in an av-bay, because if you're trying to turn everything on, you won't also accidentally turn one one of the devices off when the magnet passes by.
  • Lower standby current. The switch draws about 13 micro Amps when it's off. This is low enough to prep your rocket and button it up whenever you want to before the launch. For example, let's say you use it to connect a 400 mAhr tracker battery to a Featherweight tracker the week before a launch. But then launch gets rained out and your rocket is still prepped and waiting for the launch 1 month later. In 30 days, the switch will drain the battery by only 9.4 mAhrs out of 400.
  • The new switch's default state is off. When the battery is connected to the switch, the switch output is off until the battery turns it on.
  • High current capacity: The output FET is rated for 20 V and 24 Amps.
  • The switch remembers the last state for about 2 seconds if power is temporarily interrupted.
Are these available now, and will they be sold under the current web page for the magnetic switches? Just wondering how to order with certainty that the new switch will be sent.
 
Hi Adrian

New specs are fantastic.

One question, will the mag switch activate through CF? It should as it should have little attenuation on a magnetic field at slow passes but faster passes (like waving) I wonder if it will start inducing skin effect and attenuate the flux.

What about through an aluminum airframe? Do you have some sheet aluminum laying around (1/8") that you can see if the switch will get triggered? I am sure the magnet will induce inductive losses into the aluminum but wonder if enough flux will get through to affect the sensor.

Thanks!
 
Are these available now, and will they be sold under the current web page for the magnetic switches? Just wondering how to order with certainty that the new switch will be sent.
Yes, I don't have any of the old ones any more. I need to update the website.
One question, will the mag switch activate through CF? It should as it should have little attenuation on a magnetic field at slow passes but faster passes (like waving) I wonder if it will start inducing skin effect and attenuate the flux.

What about through an aluminum airframe? Do you have some sheet aluminum laying around (1/8") that you can see if the switch will get triggered? I am sure the magnet will induce inductive losses into the aluminum but wonder if enough flux will get through to affect the sensor.

Thanks!
I've never noticed any attenuation through conductive (and non-magnetic) materials like CF and Al. Also, this new magnetic sensor is reacting to a static magnetic field.

Magnetic induction is real (for fun drop a rare-earth magnet down a copper pipe!) , but not an issue for these switches.
 
Excellent set of upgrades! Power-off as the default state will definitely make it easier for more fliers to feel comfortable using the switch. The flipped magnet requirement helps solve an issue I’ve had when using them in 38 and 54mm MD A/V bays with redundant altimeters.

I assume if you ever do another run of Power Perches, they’ll use the new components. For larger airframes it’s hard to beat their convenience.


Tony
 
Excellent set of upgrades! Power-off as the default state will definitely make it easier for more fliers to feel comfortable using the switch. The flipped magnet requirement helps solve an issue I’ve had when using them in 38 and 54mm MD A/V bays with redundant altimeters.

I assume if you ever do another run of Power Perches, they’ll use the new components. For larger airframes it’s hard to beat their convenience.


Tony
The 29mm Blue Raven also uses these components for the built-in magnetic switch.
 
I'm a bit dim when it comes to electrical stuff, so I think I might need some help visualizing how to wire this.

In the case of a Featherweight Tracker, or other altimeters that have a + and - port for a switch (in this case a Raven with a Simple Circuit), which wires from the switch or battery connect to the +- on the board? I see only one coming from the switch, so I'm confused.

I know the answer is going to be obvious and I'll be embarrassed that I asked, but it might save me a shocking experience.
 
I'm sure other more qualified members will chime in, but here are two ways I've done it. The first is my standard layout, the second was for a temporary non-flight testing application. Hopefully the photos are obvious. I should note that with my new mounts I use the board component side up so there is no chance of them interfering with my larger 4-40 mounts with brass inserts.


Tony

First one uses a ground lead that goes to both the battery and tracker, the second uses a 'secret' ground connection that I soldered the battery lead to.
 

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@watheyak

Looking at Tony's photos..think about it as....the Gnd and +in power the switch and that the Out ..is what gets turned on and off. The Out goes to your altimeter..or other item...you'll also need to run a ground...from the battery to your altimeter

The other Tony
 
Here's a link to the ferrules and crimping tool set:

https://www.amazon.com/gp/product/B07PJK2VNT
And a photo of the switch installed other side up. That mount is for a 4" nosecone, so the mag switch is positioned so it will be easier to activate. As 'the other Tony' says, the connections are:

top '+In' connection is positive lead from the battery
bottom 'Out' is positive switched power to the device
bottom 'Gnd' can be ground for both the device and battery, but it needs to be at least the battery – the device can be grounded elsewhere to the battery

@kjhambrick – the soldered connections would certainly survive a high-G flight in my opinion, it's just that I don't have any strain relief on those and if handled too much, the wire could break right above the solder joint. But I think it would be ok for a 'permanent' installation, like a tracker mount that is just moved from rocket to rocket. Which is what would make the most sense since the wire length can't be easily changed.


Tony

(this mount is still using 2-56 screws)
 

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@manixFan --

<...snipped for brevity....>

Are the connections secure enough to fly in a hi-G rocket ?

Thanks

-- kjh
Looking at @rocketace post #46 in this thread:

https://www.rocketryforum.com/threa...-54mm-min-diameter.165955/page-2#post-2464408
He did a much better job of soldering his wires to the board – I'll use that technique next time. It also looks like he used a much larger gauge wire, which is another plus. I think @rocketace will confirm that method works very well for high G flights – I've seen a few of his 100G 'Poof' and 'Blink' flights.


Tony
 
@kjhambrick,
Soldering is more than adequate for high G flights. I have had several flights over 100G and up to 156Gs. The wires are just attached with minimal solder and the switched is just hot glued in the avbay.
One huge thing to note is what Tony said about strain relief. With any soldered connection, you need to check it before/after every flight. If the wire bends a few times as the solder joint it will fail. The below link shows a good example of all the above.

https://www.rocketryforum.com/threads/build-thread-zoom-and-poof.162044/page-2#post-2106865
 
Thanks for the link @rocketace !

Very good advice on strain relief ( Jason and Tony ) !

And I was going to ask how in the world did you capture Poof on an H999 until I saw the credits for the pictures -- Harry Spears :)

Harry is pretty amazing with a camera !

Thanks again !

-- kjh
 
Egregious show and tell of my before and after. This is an av-bay for the most forward portion of a 4" nosecone. I'm hoping I can just run the magnet around the nosecone in a circle in line with the switches, and not having to drill three evenly space holes for the screw switches and the subsequent alignment issues is great.

I made the model based on the old FW switch, but I think it's pretty close. And this whole Fusion file is a work in progress. I think its got me at about version 100 now.

AV_Dingus_Mag.png
AV_Dingus.png
 
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@watheyak --

I am not an expert here, still figuring this out. but ...

I believe the orientation of the Mag Switches around the circumference of the nose place the switch on sensors toward the inside, away from the wall.

Is that intentional ?

Thanks

-- kjh

EDIT: p.s. I really like your CAD ... what software do you use ?
 
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I believe the orientation of the Mag Switches around the circumference of the nose place the switch on sensors toward the inside, away from the wall.

Is that intentional ?
Oh hmm. Nope. I had just assumed the largest IC did all the magic. The beauty of cas is I can flip 'em 180 real quick.

EDIT: p.s. I really like your CAD ... what software do you use ?
Thanks. It's Fusion 360, which is probably the most popular for hobbyists.

Now that I have a bunch of rocketry products modeled I want to look into how to share them.
 
Scott --

Is that an Additive Aerospace Simple Circuit in your Nose Cone, just aft of the Blue Raven on the right-hand side ?

Andrew just finished a new production run and I ordered one to play with -- it should arrive Saturday or so.

It looks very ... simple ... to set up :)

How do you like it ?

EDIT: I see in you post #9 that you mentioned the Simple Circuit, so I'll bet that it is ...

-- kjh

p.s. I also looked up AutoDesk Fusion 360 ... I'll probably wait a while before I dive into that :)
 
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