Saturday, October 24, 2015

Inside stuff - Joytech ERoll

This is a teardown and 'repair' of a common type of e-smoke cigarette.

If you are reading this in the future (say, ten years from now, 2025) smoking is a type of pleasure that's dying in this year - 2015. It's an expensive drug (5-20%of monthly income) that takes a bit worse than soap and makes everything stink. It's still legal while other drugs (THC-based)  are still illegal.
It forms a strange addiction to this bad smell and lack of brain oxygenation that augments alcohol consumption. Well, lack of oxygen will strengthen any other drug or high, but can be had even cheaper while trying to stay underwater in a sink.

If you are underage and you are reading this then probably the parental filter set on the router has failed. Smoking is bad, m'kay?

If you are reading this in the future, some people here are trying to get rid of this so-called nasty habit and enrich their gadget profile. This means that the thing they are trying to replace WITH has a microcontroller, rechargeable battery and USB connection.

Enter the Joytech E-Roll - mostly sold at convenience stores and gas stations, it provides an easy entry into the world of e-smoke - the latest fab term is called 'vaping'.


Smoking introduction

As a qualified tester and having sampled the right audience (the friend who gave me this) I can offer a short opinion on this. One of the usual long-style cigarettes provides around 20 inhalations (draws). A shorter one does 10 to 15. This, on a full charge, would provide around 15 lightweight draws.

Now, to get into the mind of a typical smoker, there are two kinds of behaviors: straight to lungs or mouth to lungs. A mouth-to-lung inhaler will 'charge' the cigarette first with two-three draws, inhaling afterwards. A straight-to-lung (my term) one will draw directly in the lungs. The first user might get throat cancer while the second one is more like to get lung cancer. Choose your destiny.

There's a third type of smokers, so-called social smokers. These don't enjoy smoking but make it as an act of bravery/show-off  They will typically inhale into the mouth and 10-30% gets into the lungs while the rest of the smoke exits via nostrils and other orifices.

E-cig short review

With the questions above answered, we have two questions: how good is this thing and what's inside it?
Well, as with all entry-level e-cigs there is a lack of control with both regard to airflow and temperature. Airflow is restricted by a tiny hole (see pictures below) to a slim-type cigarette. The fact that this hole is situated where people normally keep their index finger does not help. So it cannot really break the addiction to those straight-to-lung inhalers.

The temperature is 'controlled' by the inhaled airflow - a longer draw will make the heating element hotter if the airflow is higher. However, there is a limit to this. Quick, successive draws will turn on a protection on the unit - either the 10s continuous draw one or the the battery's undervoltage limit. The internal battery is rated at 90mAh

As a conclusion, it's suited for social smokers - people that want to look cool - or slim-type smokers - those who get satisfied with a bodiless menthol flavor.

Inside stuff


The kit contains two metal 'cigarettes' and a charging station. My station charged only while plugged in, although it felt heavy as like having a built-in battery,

The cigarette charges through it's end, with the center ring being the positive connection and the outer ring and body the negative one:


This means that you can charge one with 3xAAA rechargeables, in case of a zombie invasion,, if you can control the current that is. Since the battery is rated at 90mAh you can use a supply limited at 90mA and 4.2V. Or just another charged LiPo battery and a 47 ohm resistor.


The two mating parts...

... which are actually four. Battery and circuit top left, empty tube lower left, coil bottom center, reservoir top center
 Pictures from top and bottom:



After removing the screw pictured above we can get into the unit:


The left side contains the USB charging circuit, the middle part is dominated by the battery and the right side has the latch/release mechanism for charging the cigarettes.

The circuit board does not offer many details, it looks like a generic USB emergency power supply:


Upon receiving the unit, its battery had a 0.5V potential, causing the embedded protection circuitry to ignore it:


After soldering a couple of wires for the power supply, some voltage was applied, with this result:


As you can see, it only draws 10mA at 1V.

Some time later:


... which is already above the protection circuitry voltage.

As I'm writing this, the battery draws 0.3A at 4.2V, so it must be near it's 80% charge mark.

Once again, the internal circuitry if you want to zoom in on the details:


Diagnosis


There seems to be an inherent problem with either the unit I have or in general - the red led on the charging station stays lit at all times - causing the station battery to run down and shorting my power supply. However, this is sporadic, which makes it even more difficult to pinpoint.

Another issue is the 90mAh battery life on the small units - probably enough for just 1-2 'proper' drags, 10 medium ones and at most 20 light ones. Coupled with a quoted 400 cycles LiPo survival it means 800-8000 drags, so at in the range of 2-40 cigarette packs. You have to do your own math there, including the heating elements price and the flavor packs.

The 90mAh batteries seemed to be charged directly from the main 1000mAh one, which means that on a fresh charge you would get a 'full drag' while on lower voltages you would just suck out liquid. This matches my experience as well.

The charging station is powered at all times - when a 'cigarette' is put into charge mode - so if you intend on keeping this arrangement for more than one week you will likely kill the main battery - which is precisely what happened to the unit that was donated to me.

Keeping the e-cig pointed downwards will result in inhaling liquid. It's best to keep the thing pointed horizontally.

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