Vape pens causing interference?

[needairtime]

Apologies if this is not in the right subforum... Maybe I missed it but I'm surprised there's no section about radio interference, or at least there doesn't seem one that best fits. I'd imagine any radio listener has to deal with interference at some point, and with general 2-way communication radios using fairly low power (compared to the kilowatts of broadcast radio) trying to get interference down to increase the signal to noise ratio up seems to be relevant.

Anyway, first off, I don't smoke, don't vape, etc., etc. so I don't know what's in these things and are basing it off of what I observe from other peoples' use.

I was wondering about these e-cigarettes/vape pens that apparently take 18650s to vaporize the "e-juice" that people smoke instead of burning something. I've seen some generate immense radio frequency interference to radios nearby, probably simply desensing the input. What was quite surprising is that I thought these were mostly resistive heaters which theoretically should not generate noise. It was brought to my attention that some of them use switching regulators and these quite possibly can generate hash on the radio. Anyone have either type and can verify this is the case, or do unregulated heaters also generate RFI?

I'd imagine these vaporizers need to pass FCC Part 15 rules, but do manufacturers get these tested?

And then if someone has one that generates noise, what have they done to clear the noise generated from these units short of not using them?

 

[mmckenna]

I'd imagine these vaporizers need to pass FCC Part 15 rules, but do manufacturers get these tested?

You'd think they would. Wouldn't be surprising if they were yet another product imported it without it.

Here's a video of it. Note, it's a Cheap Chinese Radio, so all bets are off on a properly filtered receiver...

Here's one that actually has a Part 15 warning in the directions:
https://www.vapepen.us/wp-content/uploads/2014/03/Puffit-Vaporizer-Instructions.pdf

 

[needairtime]

Not surprised a CCR is susceptible, but even expensive radios could be affected too. I recall an HF rig, not sure if it was a Kenwood or Icom that was affected by a vape pen as well.

Maybe I'm overlooking something for the "cheap" vape pens: the contacts that close the circuit causing noise? Though once contact is made, it should not be producing additional hash. In this respect, the SMPS if designed with a low current cutoff should not exhibit this noise source.

 

[mancow]

It's the buck converter just like cheap phone chargers. It's annoying.

 

[needairtime]

I guess it would be a type of buck converter, but with the current that needs to be dealt with...finding an inductor/capacitor that fits in the vaporizer may not be possible. The question that remains is why is the switching speed so fast? I suspect that a fairly low low switching speed is sufficient, generating noise as clicks instead of broadband hash? This is where I don't know what's needed in vape pens, perhaps it was overdesigned and undertested for radio noise?

 

[slicerwizard]

Uh, inductor size goes up as operating frequency goes down.

And switching creates square waves. And square waves have infinite harmonics...

 

[needairtime]

Well, if it's easier to filter the noise at higher frequency, why is noise still being generated? Because they're not filtering the output to be cheap. Plus the current flow will necessarily increase component size -- once again adding to cost.

If they want to be cheap, the idea is to use very low 1Hz square waves instead of doing higher frequencies and have to filter them . Resistive loads only need an average current, no strong regulation requirements are needed. At these very low frequencies, the noise pulses show up only once a second or so, instead smashing out the spectrum for the whole duration when on, at least the human ear can more easily fill in the gaps caused by the short noise pulses.

 

[slicerwizard]

Well, if it's easier to filter the noise at higher frequency

Don't think anyone said that.

If they want to be cheap, the idea is to use very low 1Hz square waves instead of doing higher frequencies and have to filter them . Resistive loads only need an average current, no strong regulation requirements are needed.

You can't run a buck converter at 1 Hz.

And a 1 Hz cycle rate on a small heating element is going to do a terrible job of regulating the temperature. Liquid will cool an unpowered element damn quick.

 

[ScannerMan1989]

Causes interference in frequencies of breath too

 

[needairtime]

Does the temperature really have to be accurate, just needs to be hot enough to stay hot -- after all, your typical stove, toasters, ovens, etc. run at many seconds duration and is effectively a "buck" converter too. Of course this depends on the thermal mass of the heater and the kitchen heaters do have at least some thermal mass. Again I don't claim to know anything about vape pens (and regular cigarettes is basically a small fire in your mouth), I don't smoke and wish all of these things would suddenly disappear, but as long as I don't have to see/smell other peoples vapors/radio hash, I don't care.

As for interference in frequencies of breath, that sort of makes sense if it's thermally regulated by the high frequency switching supply...

 

[mancow]

Yes the temperature needs to be accurate.

 

[RFI-EMI-GUY]

Causes interference in frequencies of breath too

I wonder if while someone is vaping, if they talk real close will there be modulation of the signal either FM or AM? The NSA needs to exploit this!

 

[fireadioguy]

[QUOTE=" The question that remains is why is the switching speed so fast? I suspect that a fairly low low switching speed is sufficient, generating noise as clicks instead of broadband hash? TIhis is where I don't know what's needed in vape pens, perhaps it was overdesigned and undertested for radio noise?[/QUOTE]
Shortened quote, Perhaps I may be over simplifying this, but a vape pen would need a high oscilating heater as to maximize the battery, being designed to be small and deliver high current outputs, but not shorts. So, like an incandescant house hold bulb, the current isn't constant, but is oscillated. Sure it would work on straight dc, but the filament would burn out and requires heavier wire.

 

[needairtime]

Actually, no, as in post 11, it seems that regulation is a problem. There's no problem feeding a lamp or heater DC, incandescent flashlights and oxygen sensors in cars both use DC just fine, sure they burn out but AC lamps and heaters burn out too. It's a "want" not a "need." The faster switching speed will allow the feedback control system to make changes to the system quickly as things change depending on how fast the user is sucking up the vapor -- that is if it really is feedback controlled which I don't know either as I do not have and do not intend to have one of these units.

I thought that regulation was NOT the issue because cigarette users have VERY hot smoke going down anyway, and all one really needs in a vaporizer is some sort of mass air or pressure sensor and turn the heater on only when someone draws vapor. But perhaps keeping the the coals hot and at the same temperature easier/cheaper, though at the heat necessary to vaporize, a low offset low noise amplifier is needed to provide the feedback voltage... if someone has a reverse engineered schematic I'd love to see it.

 

[RFI-EMI-GUY]

Apologies if this is not in the right subforum... Maybe I missed it but I'm surprised there's no section about radio interference, or at least there doesn't seem one that best fits. I'd imagine any radio listener has to deal with interference at some point, and with general 2-way communication radios using fairly low power (compared to the kilowatts of broadcast radio) trying to get interference down to increase the signal to noise ratio up seems to be relevant.

Anyway, first off, I don't smoke, don't vape, etc., etc. so I don't know what's in these things and are basing it off of what I observe from other peoples' use.

I was wondering about these e-cigarettes/vape pens that apparently take 18650s to vaporize the "e-juice" that people smoke instead of burning something. I've seen some generate immense radio frequency interference to radios nearby, probably simply desensing the input. What was quite surprising is that I thought these were mostly resistive heaters which theoretically should not generate noise. It was brought to my attention that some of them use switching regulators and these quite possibly can generate hash on the radio. Anyone have either type and can verify this is the case, or do unregulated heaters also generate RFI?

I'd imagine these vaporizers need to pass FCC Part 15 rules, but do manufacturers get these tested?

And then if someone has one that generates noise, what have they done to clear the noise generated from these units short of not using them?

How did you first notice this? Have you looked at the emissions with a spectrum analyser? I would imagine this is sort of a comb generator with the harmonics radiating strongest around the resonance of the heating coil. I wonder if this could be exploited to detect people in the battlefield using these devices. It would be an OPSEC problem like the using the FitBit.

 

[needairtime]

The first time I saw how bad this was ... a fellow ham was using one by a HF rig. It completely splotched out the HF rig when it was turned on! I don't have a spectrum analyzer and don't know how these vape pens are truly made, but this thread has given some very good ideas of what's in these things. I can pretty much guarantee that vape pens are not fully filtering the output. Resistive heaters do not care about ringing or overshoot, only RMS power matters. The filtering is only for RFI if they were designing for it.

Now what I suspect is in these things is a "high" frequency thermal feedback, probably MOSFET switching regulator using NO filtering - no capacitors, no coils except the minimal amount in the resistive heater. So, *theoretically* during the initial heatup it should be quiet, but when it's in regulation phase, it will be turning on the 40-80 amperes of current needed for the heater on and off. Ideally fast, but even if it's fast, what kind of wire do you need to build an inductor to soak up the transients as the MOSFET turns on and off? Normally you need... AWG 8 perhaps wire? and a few turns of AWG 8? And put that on a ferrite? And still need a capacitor and diode or another MOSFET as freewheel.

I kind of doubt it, and they're just feeding the MOSFET straight into the heater.

Unfortunately this means that every time it turns on, we get this very high current, fast pulse; and once again when it turns off. So if it's doing it at 1KHz, we get these nasty pulses a thousand times a second - whose harmonics will throw any radio into a tizzy. The "antenna" is of course the heater itself which is usually coiled. Of course that's not going to be resonant, and will happily radiate everything poorly, and probably near field would be worst.

So luckily the antenna is poor so it's not going to go very far. The voltage is fairly low except for whatever the inductance of the coil and stray capacitance tunes at, but inverse square will tend to make the signal fall off fast, except for that tuning frequency which may be detectable at distance. I'd imagine it wouldn't go too far but this is just speculation. I would think there are a lot of other things that would generate more noise.

As for talking while vaping, I don't think anyone would be talking while taking a puff, so it's a non issue. And even then, the "sampling rate" would be equal to the switching rate, but the switching current would so far dominate (I'd say over 140dB but just a guess) any signal coming from voice, it can't be detected.

 

[RFI-EMI-GUY]

40-80 amps at 4.2 Volts!!!

I can't imagine putting one of those lithium ion hand grenades in front of my face. I would sooner smoke a 20 pack of "coffin nails". Very nasty dangerous habit.

 

[needairtime]

Some of those vape pens use two 18650's to get more power into those heating coils too.
After a bit of research I think I perhaps overestimated the upper bound since the heat of vaporization of vape juice is lower than of water, so perhaps 50 amps (at 4 volts) would be the upper bound, and maybe 25 amps would be the absolute lower bound. Again this depends on the characteristics of inhaling the stuff, something I don't do... would be nice if someone knew for sure. Then again perhaps my estimates were correct at first because 150-300 watts isn't enough to vaporize water fast enough either?