My vaping device operates in two modes, variable temperature control (VT) and variable wattage (WT). The unit first sends out a ~1 second 30 watt/7.74 volt surge to the coil to see which mode it should use(according to the coil you installed). This spike is actually a design flaw in the firmware, it should happen in a fraction of a second and basically unnoticed, a return or refund is not an option anymore. An updated firmware does not do this. What this spike does is scorches the coil and the ejuice and then hurts your mouth, throat and lungs. My question is: I personally need a maximum of 7.0 watts/3.74 volts so could I not just install a resistor, diode, voltage regulator... (close to 7.0/3.74v range) between the control board and coil connections to prevent or absorb this 30w/7.75v spike?

  • \$\begingroup\$ A flyback diode will prevent a coil (inductor) from spiking, and damaging circuitry. \$\endgroup\$ – user86234 Apr 24 '16 at 23:43
  • \$\begingroup\$ If I understood correctly this is actually something you bought? Isn't updating the firmware an option? \$\endgroup\$ – Barleyman Apr 25 '16 at 9:28

A current limiter is probably the most straightforward way to do this. Check out this answer: https://electronics.stackexchange.com/a/229893/106823

NB that transistor should be AFTER the load coil. Also pay attention to transistor base voltage versus current, you have a lot more current than the 20mA LED circuit. You're probably looking at 0.7V, not 0.6V.

You can also implement this with a mosfet as well but a transistor may be easier to pull off.

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