MEMM

[MeggerMan]

Pulse output results so far:
12 ranges tested with the capacitor leg lifted off the breadboard and coupled direct to the capacitors. Some of the capacitance values where I combined 2 or more capacitors have been measured with a TENMA 72-960 LCR meter.

Resistance swing is 9.95kR - 52.8kR using a 47kR trimmer and a 10kR resistor.

1. 200kHz - 533kHz 22pF,
2. 80kHz - 300kHz 110pF,
3. 25kHz - 110kHz 468pF,
4. 12kHz - 35kHz 1200pF,
5. 6kHz - 20kHz 2200pF,
6. 3.5kHz - 12kHz 3.9nF,
7. 1.2kHz - 5kHz 10nF,
8. 600Hz - 2kHz 22nF,
9. 300Hz - 1000Hz 47nF,
10. 155Hz - 500Hz 89nF,
11. 100Hz - 290Hz 146nF,
12. 40Hz - 132Hz 386nF

Other ranges I also tested that will not be included in my 12 frequency range pulse unit:
25Hz - 80Hz 600nF
13Hz - 40Hz 1.1uF
5.7Hz - 17Hz 2.5uF

Note that the ranges 11 and 12 and the 3 above all had a some level of double pulsing:
Example, the first output of the TL494 - Q1 would show two pulses widths together and the output for Q2 would at the same period show two spaces, which is fine, except that the frequency is now altered slightly.
It is quite rare, only occurring once every 2-3 seconds or so.
This is not bad going considering the chips minimum frequency is specified as 1Khz and I am pushing this down to 5Hz.
I think I have improved the stability by applying a 0.1uF capacitor across the GND and Vcc.

Next step is to test a MOSFET coupled to it and then design a PCB for it all.

The front panel will have:
12V in (pulse supply)
power LED
0-30V in (MOSFET supply)
A out
B out
f Range select (1-12)
f fine tune
duty adjust
output control switch(push-pull / push)
I will leave a space in the top left of the panel for a 2-line LCD display for future expansion. (frequency and duty info display)

So far so good.

Regards

Rob

[eldarion]

Count me in on the replication project!

I ordered my Metglas C-cores today, hopefully they will come in the next couple weeks.

Excellent work Paul!

Eldarion