Re: [EVGRAY] Re: SCR TURN ON AND OFF INFO FROM FILES

Body

Warren, 

 I will have to take another look for surplus around here, don't think there is much of that within 250 miles.
 

 There is a metal recycling place that sometimes rarely has these but they usually try for more than 20 bucks.
 

 Ah the magic of large cities and dumpster diving!
 

 I do keep my eyes out for curbside motorized excercise equipment like treadmills and such.
 

 By the way I picked up a cheap Chinese inverter 220 3000 watt, so probably good for 1000 watts near full duty.  Would not trust it as is, they were too cheap to use micas to seperate the fets from the heat sinks and used little silicon tubes cut to 3/4 inch over each piece of silicon.  Of course no theremal paste, does not bode well for future use.
 

 Anyhow the circuit is quite handy as it has two TL494's and four transformers.
 

 Have you had a look at all one can do with a 494?
 

 It's very fast 500ns, very hard switching with a wide frequency response determined by either an outside triangle pulse like a signal gen or it's own internal oscillator and an R/C like a 555 or another 494 it slaves to.  A wide frequency range and voltage adjustable duty cycle by how much DC one of the pins sees.  There are two driver sections that run parallel or push pull, one to drive fets right at their gates and a flip flop that runs at either 50 or 60 cycles to drive something else like SCR's to switch the whatever one does with the first section to square wave AC.  
 

 I wish the last part flip flop was variable too but I think it's programmed at 50 or 60hz but the first part is still there to toy with.
 

 This inverter is called modified sine but there is nothing sine about it, super hard square edges.  Of course one could add the filters and such to get a better representation of a sine but otherwise this thing can be hacked into 2 channels of push pull variable frequency coil pulser/drivers.
 I think the frequency is good from around 1k to 300k and can be driven right from a function generator or two.
 

 Anyone here hacked a 494 while still inside a cheap inverter to pull variable frequency energy before the last FWB?