Hi.
I'm trying to control an old CRT using a microcontroller, and I need to drive the deflector coils with reasonably large voltages.
I've got a few questions I'd really appreciate some help with:
- To deflect the beam both ways, I need to be able to apply a positive and negative voltages to the coil. Simplest way, I figure, is to bias one side at a mid voltage, and swing the other beween 0 and the maximum. Does this sound reasonable?
- I'm not sure how to switch the larger voltage using the microprocessor's 5v output. I could use PWM to control a mosfet in saturation, or get an analogue voltage via a resistor ladder, to operate it in linear mode. How would I go about doing either of these, and as I understand I need Vgs to be greater than Vds in either case?
- The coil has a resistance of something like 60ohms. How should I isolate it from the power supply, so as to prevent it effectively shorting the supply when connected by the mosfet?
Any help would be greatly appreciated!