PSU boards

I unpacked the boards last night - they look great. The only thing I didn't realize before ordering is that they are not gold plated, in this regard oshpark still has one up on DirtyPCBs. I got 12 cards so still very pleased.

DirtyPCBs

I got the cards for the power supply today, from DirtyPCBs. I ordered them about three weeks ago, not to bad I think. The quality looks good too, though I haven't unwrapped them yet. I got 11 cards for around $25, a VERY reasonable price considering the cards are 8x10 cm.

 

DAC and S&H boards arrived

The DAC and sample and hold PCBs arrived from oshpark today. They look great as always, I am very excited about them and wether they'll work or not. 

I will start ordering parts today too, I have two populated shopping carts, one with Farnell and one with Rs components and will press submit as soon as I get an answer from Farnell about the value of the Tempco resistor they offer - the data sheet indicates 1k but their page says 100Ohm... 

Transformer power ratings

Transformers are usually rated in VA. The power rating is the same on both the primary and secondary windings.

To calculate how much current you can draw from the transformer, just divide the VA rating by the secondary voltage:

A 10VA / 12V transformer will supply 0.833A.

For dual secondary transformers, the rating is for both secondaries combined. To get the maximum current for each secondary, divide by double the voltage:

A 60VA / dual 18V transformer will supply 60 / 36 = 1.67A per secondary.