I want to make a 400 watt switchable ballast.Can I build the ballast for a hps and add a switch to bypass the igniter for mh or do I need to get 2 different transformers and two different capacitors? What do i need to ask for when i go to the electrical warehouse? I built the housing out of alum and a computer fan and i have heavy duty wire and a mogul base already.
yeah man just get a switch to bypass the ignitor. That is if it is an hps ballast. The MH bulbs have one built in. I know of a fire that started becuzz of this! Be careful and make sure yuou get parts with all the correct ratings!
It usually tells you on the box not to interchange ballasts, but I know someone who has done it successfully for almost two years now (in a detatched garage). I definately wouldn't do it in a house or apartment, though. I wouldn't do it personally, at all. I would just use the MH for vegetative, and then switch to the HPS for flowering once you get the right ballasts for the bulbs.
