18-03-2017, 03:23
(18-03-2017, 02:09)clubjoker Wrote: And so I'm curious to know why that 470uF capacitor on the output side is in the design. The only explanation I can come up with is that it's for giving a bit of ooomph juice for starting up a fan motor (for a temperature sensor) from stationary. I'm reckoning that its got nothing to do with the relatively low power radio transmitter. So if I'm not having a fan, can I use just a ceramic 100nF? I'm going to look back at the archive of pre-fan circuits to see if I can get more evidence...
Could someone explain this? Maybe the chief designer himself?
Thank you
You are right... this large capacitor helps to give "juice" when the fan starts, but that is not all. There is another voltage regulator on the circuit, an AMS1115, so, you can look at C3 to also as the capacitor on the input of the AMS1115. Anyway, there is no need to be exactly a 470uF cap, 220uF will do the job.