I want to go VV with my puck. Fully charged at 5.0V, so don't need a regulator. I just want a VV range 5.0V to 4.2V. Is this the correct placement for the 10k single turn POT? Do I need anything else? Any help is greatly appreciated.
VV can I do this?
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Absolutely NOT!
The potentiometer will not be able to handle the current the atty/carto coil draws. Assuming a 3 ohm atty at 4.2volts means almost a 6 watt demand. Pots usually can only handle 0.5w - only the bulkier wire-wound types go much above 1-2 watts.
It is for this reason alone that regulator circuits are used in VV mods - the variable resistance only controls the regulator and does not actually carry the load.
The potentiometer will not be able to handle the current the atty/carto coil draws. Assuming a 3 ohm atty at 4.2volts means almost a 6 watt demand. Pots usually can only handle 0.5w - only the bulkier wire-wound types go much above 1-2 watts.
It is for this reason alone that regulator circuits are used in VV mods - the variable resistance only controls the regulator and does not actually carry the load.
Even with a regulator, you'll have some trouble getting output close to battery voltage (if you want to use those higher voltages). Even low dropout regulators have some dropout which means they can only put out voltage some amount less than input voltage. To obtain those higher voltages, you'd have to add another cell which would probably be an issue for the overall size of the mod. That's probably why we haven't seen any regulated Pucks (at least I haven't noticed any).
One thing you could do that would work is to add a switch that puts one or two Schottky diodes in-line. That would give you the option to drop voltage in .5V steps.
One thing you could do that would work is to add a switch that puts one or two Schottky diodes in-line. That would give you the option to drop voltage in .5V steps.
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With the Puck-style mods, it's relatively simple to have, at least, two more batteries in the 'control' box; for a total of 6 batteries. The NiMH batteries typically come off the charger at 1.4V, so 6 batteries will give you ~8.4V. I believe it should be quite possible to have a regulator circuit fit in the 2 empty battery spaces.
Thanks for all the advice. I have a free sample switching regulator coming from TI, the same one used in the evercool VV so I guess I will add the two extra cells and go with the evercool circuit. I was just hoping for an easier way. The diodes sound like something that could be done in combination with a five position slide switch for multiple .5V drops.
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