I am currently trying to get my projects a little more automated but I'm not sure on this one. I have around 60 j111's I need to control with 8 PCF8574 I2C I/O expanders and a Propeller. The programing is done but I'm not sure how to convert the 3.2V out from the I/O chips too -15V, Would I be better off with an opto Isolator or just a transistor? What would be the best type of transistor? BJT, SCR, SSR, IGBJT, Darlington? and I would Like it in as few packages as possible, 8-16 outputs per chip if possible.