Re: SSTC probs

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Darren Freeman by way of Terry Fritz <twftesla-at-qwest-dot-net>" <free0076-at-flinders.edu.au>

At 06:42 AM 26/11/2001, you wrote:
>I tried a higher voltage supply to power the 555 and it SEEMS to help.I did

Whoa - don't use a 555 to drive the gate!!! Get yourself a nice $5 chip to 
do it - those babies kick butt and are worth every cent you spend on them 
=) So protect them with filtering caps and maybe a zener and they'll make 
your setup purr like a.. err.. coil? =)

>get twice the output but that quickly left.I was back at normal output with
>occasional better output.

Sounds like it was getting pretty hot or dying in some other way..

>I think that the MOSFET is taking too much CEMF.How

CEMF?

>
>can I block it completely?My circuit is just a plain simple 555 pulsinga
>MOSFET.The MOSFEt is directly driving the primary.

Like I said, use at least a half bridge, otherwise you're gonna kill the 
MOSFET with flyback pulses, or heat the clamp diode if it's fast enough to 
catch them.. Or do both which is more likely =)

There's lots of circuits on the Web.. look for one which has been tested 
and put in the effort to build that. There's no fun in frying MOSFETs, it's 
like crashing model aircraft because you used really old batteries for the 
radio... Just more trouble than it's worth and it makes you put it away 
after a while =( So do read books, do try a 12 V version until you think 
it's perfect, and do bother with all of those protection diodes and ringing 
suppression resistors =) It takes longer to mount another 10 MOSFETs in the 
end =)

>Matt

Darren