I'm taking a more realistic look at the circuit, and I can see some problems. The relay shorts the PWM signal to ground to fire the trigger, where as an amplifier circuit uses the PWM signal in the transistor's base as a trigger. The relay's method does put a lot more of a load on the trigger. This is not a good set up, do not try it. Put a logic level MOSFETs amplifier circuit in to the SSR's place, and you will have a good setup.
thank you very much, Luke...
TBH, the only sole reason why I keep digging the PWM controller is because I'm really curious with how the Sanyo 9SG behave.
unlike many Delta /Nidec that I have dealt with, this 9SG got something more like the "electrical noise" issue.
I've boosted my last 2-98% version (the red one) with another single 555 (from TI) and I'm quite sure that it have been fixed.
I'm still curious how it will behave if I use another 555 from another manufacturer, since on my previous attempts the 9SG would exhibit those electrical noise whenever I connected it with the 2-98%.
then, I still got few 555 with cmos version to give it a try
about this electrical noise on the 9SG, I feel I really need to upload it on youtube or something to describe it better.
but up till now, I can't manage to make a decent vid nor a record, I'm trully sorry.
the electrical noise is something like this (the vid's belong to Nothor):
the interesting thing is, I also had similar noise when I set the 0-100% real close to 16kHz frequency.
going under 16kHz to (say something around 15kHz), the noise became louder. especially when the fan spin lower.
I recalculated the 2-98% on the low pot setting with 100k ohm + 470pF, and it did resulted around 15.xx kHz.
very similar pattern, huh?
now, I can get away with the additional 555 as a booster, but the fan still spinning around 1.1k rpm on their lowest pot setting.
it still noisy, but the noise is more like mechanical than electrical to me (maybe because of it's aluminum frame, like Arkade mentioned before).
I'm still trying to damp it with rubber (but still got no time to do it).
it really interesting to implement your design with the NPN silicones,
due to its wide availability in mA to A.
and it's super simple too.
I'm still unsure with the, SSR.
since I never visit the automotive section in the city.
I'm still a minor to mod the car
but thanks for all your harwork, redrawing the connections lines