Kapanadze Cousin - DALLY FREE ENERGY

[itsu]

Nick,

that 1Khz is very low considering you use a 1nF cap with 20K pot, so that points to a wrong/missing connection somehere in your circuit as you have already changed the TL494 chip, i think.
Make sure your pin 14 (+5V) is unconditionally stable.

Itsu

[NickZ]

  Itsu:
  As my frequency was too low, I replaced the 4k resistor on the 50k pot with a 1k resistor. This raised the frequency to about 5KHz, from the previous 1KHz. But, I think that even if I remove that 1k resistor, and replace it with a 100 ohm resistor, my frequency would still be low.
   Ideally we need 5KHz to 30KHz range. But, to reach that point I'd probably have to change the 50k pot, as well.
   Can it be replaced with a 20K trim pot, instead, if needed. And replace the now current 1k resistor with a 10k resistor, also?
  Your thoughts...

   The duty cycle controller works a bit better now, and shows little to no glitches, while running at the higher frequencies, such as 2.5KHz to the current 5KHz. So, I would think that at the right running frequencies, (15KHz to 27KHz), possibly the signals might be stable.
   I got these readings by using the two 10k resistor on the 24v input from the PSU, going to the fets, with the Fets installed.
   

[itsu]

Nick,

The 4K versus the 1K only makes a difference when the series 50K potmeter is set to 0 Ohm.
But if you really have a 1nF (0.001uF) cap for C4 it should have changed the frequency from very high (200KHz) to somewhat lower (130Khz), see
the TL494 data sheet Fig. 1 which shows the relation between the RC used and the frequency (that is with the 50K pot set to 0 Ohm)

With 1nF cap (0.001uF) and 1 to 50K resistors the frequency should operate in the red area, see picture.


If you say you are running between 1 and 5Khz (and still have a 1nF cap), then the resistance should be something like between 300K and 1M Ohm, see the blue area.

OR...... you do NOT have a 1nF cap, but a 10nF (0.01uF)

So double check the C4 cap make sure it really is only 1nF!
If OK, then there must be something wrong with your resistors/pot.  It looks like they have way to much resistance (300 - 1M Ohm) causing the frequency to be so low.

Itsu

[NickZ]

   Itsu:
   Although my C4 cap has always been the same ceramic disk cap which I thought was a 102 (0.001 uf), it is NOT a 102, but a 104 (0.01uf), instead. So, that explains the low frequency readings. 
My eyesight is not what it used to be, either. I had to use a magnifier this time to see the numbers on it more clearly.

  According to the data sheet, TL494 chip is not meant to run at lower frequencies than 1KHz, so that may also explain why my circuit goes haywire when it's readings show less than that lowest 1KHz operating frequency. Which it does anytime it's not at the maximum frequency on the 50k pot.
  So, it looks like you have solved another issue of mine.
Now I wonder if that has anything to do with the fet overheating issue, also.
  I'll change the 104 for a 102, and report back. You've made my day.
                    Thanks, again.
                                           Nick
 
 
   

[itsu]

Nick,

ok,  good to know what the problem is, but be aware that a 104 marked capacitor is NOT 0.01uF, but 0.1uF, see this chart:
http://grathio.com/assets/capacitor_tags.pdf

Hopefully this also solves the heating problem with only the 10K Ohm resistors at the drains.


Regards Itsu