Need Help - Magnetic Switch - Dual EasyMini Altimeters

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DevSteph

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Hello, I'm trying to use 1 Feather Weight Magnetic switch to turn on 2 Easy Mini Altimeters. I don't want to run 2 magnetic switches for fear of not turning both on with the magnet pass, and/or turning one of them back off. Push button switches are not an option (as I'm installing the electronics tray up inside of a Loc 7..67 nose cone with limited space through the bottom hole. I tested running 1 altimeter with the magnetic switch (9v battery connected directly to the altimeter), (ground from 9V to ground on magnetic switch), (altimeter on switch to magnetic switch in), (altimeter switch on to magnetic switch out). A magnet pass was able to turn the altimeter on and off. However, my concern is can I run both EasyMIni switch outs to the same single Feather Weight magnetic switch (in/out)'s and not hurt/affect the performance of both altimeters. I checked the EasyMini schematic and it appears there is power interruption to activate the unit in the switch port. I'm just concerned about hooking both of those power interrupts via the Feather Weight switch to arm them. Should still be 9v parallel but double the amperage, correct? Any other concerns of both electronics firing with the battery draw? Or is the dual 9v sufficient? Really appreciate anyone's input with this arrangement.
 

Cameron Anderson

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Drop the 9 volts, you need lipos...probably a 7.4v 800mah to power both altimeters. But you want to check the magnetic switch capabilities and the EasyMini requirements to be sure I only use 3.7v 150mah with my switches to power my Ravens. But no 9 volts, that's for sure.
 

GlueckAuf

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If you're going with redundant altimeters because of the Level 3 design requirement, I'm pretty certain you're required to employ two separate altimeter switches as well. If you design your avionics bay to position the magnetic switches at least six or so inches apart, and mark each switch's location externally, I think you'll solve the issue of balky on/off switching. My own Level 3 sled pictured below uses two Featherweight mag switches located at opposite corners of the sled and I have no problem with separate actuation of the switches. Dual Featherweight mag switches will ensure your recovery system electronics are fully redundant, and render your other concerns moot.

Good skies,
GlueckAuf

1626327078502.jpeg
 

Voyager1

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If you’re aiming for proper redundant dual deployment then you require separate batteries and magnetic switches for each altimeter. The magnetic switches should be separated on the sled so that they can be controlled independently without interference.
 

ksaves2

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I remember a discussion many moons ago about the FW magnetic switches. Unless things have changed, they were not considered appropriate for L3 certification (at that time) by a fair number of TAPS unless there was a mechanical switch involved. (Heck, why do both?) The FW mag switch (I have a couple) work well. Many TAPS wouldn't accept it and I suspect the L3CC's didn't like them either. That was several years ago and views might have changed since then. I would not start a project for an L3 certification without getting the mag switches cleared with the TAP/L3CC. If they say "no", it's best to know that right away so one can plan on using mechanical switches at least to get the cert out of the way before they find out they have to change out the electronics bay.
I've flown a single altimeter in a near minimum diameter project with a FW mag switch without problem. Gets 10k' on a J and has a GPS tracker nosecone.
I like the mag switches and I do a startup test with bare contained ematches on an installation to make sure the mag switch defaults to "off" with the battery applied or I turn it off with the magnet if not. When that test is cleared, I disconnect the battery, load the charges and leave the battery disconnected. When I arrive at the field, I connect the battery and make sure the mag switch is "off". Put rocket on pad, swipe with magnet on the outside marked arrows and wait for the altimeter to cycle and give the ready beep. Simple.
Kurt Savegnago
 

GlueckAuf

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I remember a discussion many moons ago about the FW magnetic switches. Unless things have changed, they were not considered appropriate for L3 certification (at that time) by a fair number of TAPS unless there was a mechanical switch involved. (Heck, why do both?) The FW mag switch (I have a couple) work well. Many TAPS wouldn't accept it and I suspect the L3CC's didn't like them either. That was several years ago and views might have changed since then. I would not start a project for an L3 certification without getting the mag switches cleared with the TAP/L3CC. If they say "no", it's best to know that right away so one can plan on using mechanical switches at least to get the cert out of the way before they find out they have to change out the electronics bay.
I've flown a single altimeter in a near minimum diameter project with a FW mag switch without problem. Gets 10k' on a J and has a GPS tracker nosecone.
I like the mag switches and I do a startup test with bare contained ematches on an installation to make sure the mag switch defaults to "off" with the battery applied or I turn it off with the magnet if not. When that test is cleared, I disconnect the battery, load the charges and leave the battery disconnected. When I arrive at the field, I connect the battery and make sure the mag switch is "off". Put rocket on pad, swipe with magnet on the outside marked arrows and wait for the altimeter to cycle and give the ready beep. Simple.
Kurt Savegnago
Sometime after that infamous 1,313-post TRF thread regarding Wi-Fi and magnetically-actuated DD altimeter switches was finally locked, the following was announced.

1626638750001.png


Your SOP is sound, as I interpret it and the 18 October 2020 Tripoli announcement.

Inhibited NOW apparently means the powered-up Wi-Fi or magnetic switch is in the OPEN state (and thus, the DD altimeter is unpowered). The announcement clarified that simply because the remote-control switch is itself powered (as it MUST be to function), the pyro system is considered inhibited so long as that powered, electronically-actuated switch is in the OPEN state and NOT supplying power to the DD altimeter. No separate mechanical switch is necessary to achieve the "inhibited" state, thankfully.

But even under Tripoli's original NFPA 1127 interpretation, wireless switching of "unapproved" switches (like the Featherweight magnetic switch) was still allowed by Tripoli in a high-power rocket design. It just demanded that, post-RSO inspection, a separate e-switch power-up/e-match connection area was established safely away from the crowd before power was applied to the electronic switch OR before a pyro-initiating e-match/glow plug/flash bulb (or the like) was electrically connected to the pyro terminals.

BTW, the Featherweight magnetic switch retains whichever state, open or closed, it was in when power was last disconnected from it. Best practice seems to be to magnetically switch it to the OPEN state (altimeter OFF) before its battery is disconnected. That way, it will not spontaneously power up the DD altimeter the next time the battery is connected to the switch.

Good skies,

GlueckAuf
 

ksaves2

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Thanks for that above history and post. So I assume one could do a dual deploy level 3 project with 2 devices controlled with two FW mag switches and it would pass muster? As long of course as it was a well built installation.

Kurt Savegnago
 

GlueckAuf

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Thanks for that above history and post. So I assume one could do a dual deploy level 3 project with 2 devices controlled with two FW mag switches and it would pass muster? As long of course as it was a well built installation.

Kurt Savegnago
Yes, per the photo of my L3 sled in post #3 of this thread, Kurt, that’s precisely my chute deployment design for my own Level 3 project, to be attempted in less than a month. I’ve safely and successfully flown and recovered the candidate rocket several times with this recovery setup. As long as it behaves identically with a Loki M1378 as it has on the variety of H and I motors it’s burned on shakedown flights, my Level 3 bird should pass said muster, at least operationally. Withstanding Mach 1.5 velocity vs 136 mph will be but one of many unique differences...but that’s what the hobby’s all about, eh? :)

Good skies,
GlueckAuf
 

cerving

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The TRA reboot basically reaffirms that electronic switches that shut off current flow to the energetics are to be treated the same as mechanical switches. Off is off... the electrons don't really care how it's done.
 

ksaves2

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Nice,
When the mag switch came out, I argued online with TAPS about it and just dropped it as I couldn't convince any of them. Glad the reality came to light over time.

Kurt Savegnago
 

maddmaxx11

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Anyone use the eggtimer WiFi switch? Just put one together today and it seems to work good.
 

cerving

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Judging by how many of them we have sold, I would guess that quite a number of people are using them...
 

maddmaxx11

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I had seen something that said TRA and NAR requires a mechanical switch. Did that change?

I like the kit and plan to get a Quantum next.
 
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