Rick said:
Can you tell us if there should be any difference in AC vs DC going into the heater?
I'm no electronics expert, but theoretically, there should be no difference in terms of the average amount of power going into the Zap. A 12VAC power supply delivers, on average, 12V. However, the power is delivered as Alternating Current, which means that it is constantly changing and reversing polarity (60 cycles a second in the US). In order to supply the average of 12V, this means that on each cycle the voltage will peak at about 17V twice per cycle. This means that the resistor is receiving much higher amounts of power for brief periods. I don't know what effect this would have on the longevity of the resistor, but it seems to me that it would place the resistor under greater stress than DC, which is a constant 12V.
All of that aside, the other thing about a 12VAC power supply is that it uses just a simple transformer to step down the voltage. While this is great for simplicity and reliability, there is no regulation of the output voltage, so if the input voltage is lower than normal, the output voltage will also be lower. An unregulated DC power supply is no better, it is simply a transformer with a rectifier on the output so that there is no reversal of polarity during each cycle.
On the other hand, a
switchmode power supply will deliver the rated DC output (+/- whatever tolerance it has been manufactured to, probably 5%) regardless of the input voltage. Another advantage of switchmode power supplies is that they are very efficient, lightweight, and inexpensive. They also take a wide range of input voltage eg, 90 - 250VAC, so the same unit can be used anywhere in the world. The disadvantage is increased complexity and possibly lower reliability, but this will vary depending on manufacturer.
If you want to maintain a more consistent customer experience, you could provide a matched switchmode power supply with each Zap kit. By this I mean that you could measure the resistance of each Zap, and the output of each power supply, then pair up a higher resistance with a higher voltage power supply, or a lower resistance with a lower voltage. Any variation in performance would then be due to the type and amount of wood used, having eliminated the other variables.
MaquinaVapor said:
I imagine that with more current I might reach higher temperatures and also heat it up faster, am I correct? However, what's the maximum current we can supply to a rockzap? the standard power supply is 1A.
You only need a 1A power supply. The first one you listed will work. You could use a 1 million amp power supply and it would not make any difference. The Zap will only pull the amount of current that it needs. You wouldn't want to go below 1A though, as the Zap would try to pull more current than is available, thus overloading the power supply. To get higher temperatures you would need a higher voltage.