Jul
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Over-currents and short-circuits are almost unavoidable when working with rebuildable atomizers and mechanical mods. Usually caused by bad atomizer resistor set-ups, shorted wires and wrong connections, sustained over-current conditions always lead to battery overheating and, under extreme conditions, battery and equipment damage. Make-break contacts in mechanical mods are among the first components that may show signs of degradation after a sustained, hard short-circuit.
VV/VW mods usually include dedicated over-current protection that acts fast to interrupt current flow if a fault occurs. However, mechanical devices usually score quite low in terms of safety — since they are designed to be simple / rebuildable, they usually come without any protection circuitry at all.
Collapsible springs, which are often used to provide a basic level of short-circuit / overheating safety, are too slow to prevent battery and equipment damage, since they react only after the battery has already overheated. High-drain IMR batteries, which are the de-facto standard for use with mech mods, come with no integrated protection circuit boards. This leaves us with very few options for protecting our gear and minimizing the risks of battery and equipment failure.
Resettable polymeric fuses have been around for quite a while – they provide an easy means of secondary over-current protection, which is fast enough to prevent component and battery damage. These fuses do not ‘burn’ like the traditional ones – they use a polymeric element that interrupts the circuit during an over-current condition.
A characteristic property of polymeric fuses is that the tripping time depends on the current and the ambient temperature. These devices operate with a relatively static resistance and almost linear voltage drop characteristic at currents lower than a threshold current. Above that threshold, the resistance of such a device increases progressively faster with higher current values. Therefore, proper component selection is key to ensuring a good balance of performance and safety. Additionally, since the response of a PTC device depends on the short-circuit current, using a high drain battery with a low internal resistance and high discharge rate actually ensures that the device will trip faster.
The Bug, designed and manufactured by Atmizone, houses a carefully-selected, high-amp polymeric fuse. The device is rated for operation up to 7 A at 40 degrees Celsius and has been designed to trip in about a couple hundred milliseconds when hard-shorting a low-resistance mod powered by a high quality IMR battery. The device will also trip within a few seconds when conducting currents above 8 A.
Practically, this means that the Bug can be used with atomizer resistances down to 0.6 Ohms, introducing a resistance in the range of 20-30 mOhms — lower than the internal resistance of an AW IMR. Typical voltage drop values are 0.05 V at 2 A, 0.12 V at 5 A and 0.18 V at 7 A.
Thanks to its compact size (D=18.3mm, L=~5mm) and no polarity requirements, the Bug can be used with all telescopic mods and quite a few fixed-length mods with extra tube space.
It can be used in the Roller as a replacement of the collapsible spring for:
- added safety,
- extra performance,
- zero maintenance, thanks to its silver-plated top and bottom contacts.
The first version of the Bug is already available in our online shop.
