Island 12V noise filter for CCD spectrometer
Schematic & Board Layout (PDF):
Schematic
PCB Silk
PCB Tracks
PCB Solder
Express PCB Cad Files
Schematic
Board Layout
Pictures of noise filter
Top view of PCB
PCB in enclosure
Bottom of PCB
Bottom of PCB tinned
Scope pics of the power supply noise without any noise filter (about 1V of noise)
No filter, 6A draw, AC coupling, 200mV/div
No filter, 6A draw, DC coupling, 2V/div
Scope pics of the noise with a 10,000uF generic electrolytic on the PS output (a quick test). Note: The noise is about 200mV (five times smaller)
10,000uF electrolytic on PS output, 6A draw, AC coupling, 100mV/div
10,000uF electrolytic on PS output, 6A draw, DC coupling, 2V/div
Scope pics of the output of the noise filter with a 6A load (as shown in the schematic). Note: The noise is about 25mV (about 40 times smaller than not using any filter).
With filter, 6A load, AC coupling, 20mV/div
With filter, 6A load, DC coupling, 2V/div
Setup to test the noise filter at 6Av
Scope pics of the output of noise filter with no load to light load (as shown in the schematic and pics). Note: The inductors don't do much at no current or very low current. With no load, the PS goes into a more efficient mode where it pounds the output about three times a second and causes about 70mV spikes. At 12mA the power supply looks to the switching frequency is around 66Hz and the ripple has dropped to about 35mV. At 120mA it's switching at about 570Hz with a ripple around 20mV.
With filter, no load, AC coupling, 20mV/div
With filter, 12mA load, AC coupling, 20mV/div
With filter, 120mA load, AC coupling, 20mV/div
Brief description of how the filter works
noise filter readme.pdf