I’m giving my grow light more horsepower this year. I did a little research on fluorescent bulbs and learned that the bulbs will withstand higher current flow, which results in higher light output. This higher output comes at the cost of higher energy use and lower bulb life. A common way of achieving this is ‘overdriving’ the bulbs by rewiring the fixture. There is lots of information on the interwebs about this, and it is pretty confusing because most of the information seems to be written by people who have accomplished something without understanding what is really going on. Here is my explanation:
Fluorescent bulbs have the property that they conduct better as they heat up, so it is critical that the current be controlled through the bulb. This is the job of the ballast. Traditionally this was done by taking advantage of the fact that standard electricity changes direction 120 times per second and the properties of an inductor to limit fast current changes. These types of ballasts are known as magnetic, and are the cheapest ones you can buy today. Modern times brought electronic ballast that are more efficient because they increase the switching frequency to send more pulses to the bulbs per second.
Using an electronic ballast, it is possible to drive a single bulb with the output intended for 2 bulbs (or 3 or 4). The cheapest (initially) way to accomplish this is to buy 2 cheap shop light fixtures from Home Depot ($10 each), remove the ballast from one of the fixtures and install it in the other fixture. Rewire both ballast so that each ballast (designed to drive 2 bulbs) drives only one bulb. So for $20, you have one fixture with 2 ballast, and one fixture that is now a skeleton. For the fixture that is cannibalized, I’m going to use a single new electronic ballast designed for 4 bulbs, and wire it to power the 2 bulbs.
Notes: Continue reading →
