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The 470 capacitor mystery deepens
A quick update with progress - the spanky new PCB etched a treat (I found out today that etching boards face down rather than face up takes about a tenth of the time - and if you heat the etching container in a bowl of warm water, the same way you use a bowl to melt chocolate, a full 100mm x 50mm board takes about four minutes to etch. 45 minutes is not normal etching time!)
I mounted the components onto it and soldered everything down.
It was the point of no return now - plugged the board into the USB on my PC and everything still works! It still detects the device as a native USB/HID device and I can enter a VID/PID combination and retrieve data from it. Brilliant.
But here's the weird bit.
I'd used a 470uF capacitor to tie Vusb to ground. Although this was using the wrong units, I assumed that there'd been a typo because on other sites and forums, 470nF was recommended.
Anyway, I bought some 470nF and some 470uF capacitors, as well as some 220nF caps (since some sources recommend 220nF capacitor for Vusb). The crazy bit is that the 220nF capacitor doesn't work: the device appears but Windows says that there's a fault with it. But if you use either a 470uF OR a 470nF capacitor to connect Vusb to ground, it gets detected as a valid USB device. Even though one capacitor is 1000 times the "size" of the other.
I still don't get it, but since 470nF works, and a lot of other sources recommend this value, that's what I'm going to stick with. I just don't understand why 470uF also works.....
I mounted the components onto it and soldered everything down.
It was the point of no return now - plugged the board into the USB on my PC and everything still works! It still detects the device as a native USB/HID device and I can enter a VID/PID combination and retrieve data from it. Brilliant.
But here's the weird bit.
I'd used a 470uF capacitor to tie Vusb to ground. Although this was using the wrong units, I assumed that there'd been a typo because on other sites and forums, 470nF was recommended.
Anyway, I bought some 470nF and some 470uF capacitors, as well as some 220nF caps (since some sources recommend 220nF capacitor for Vusb). The crazy bit is that the 220nF capacitor doesn't work: the device appears but Windows says that there's a fault with it. But if you use either a 470uF OR a 470nF capacitor to connect Vusb to ground, it gets detected as a valid USB device. Even though one capacitor is 1000 times the "size" of the other.
I still don't get it, but since 470nF works, and a lot of other sources recommend this value, that's what I'm going to stick with. I just don't understand why 470uF also works.....
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