A commenter asked for the schematic of the analog interface I made using an MPC3008. I seldom include schematics with my posts for several reasons. I don’t expect anyone to duplicate exactly what I have done, so if I post anything, it is just partial drawings of the most important concepts. But the biggest reason is that I almost never create true schematics and I am too busy to do it just for the blog. Something that I do frequently do is a simple drawing that helps me lay out the components onto the perf board. Then I use that as my guide when I build the device. These are seldom complete enough to be useful to others. In this case, however, the entire circuit is shown.
This is what I created for the analog interface. The 7-pin header connects to my main circuit board where I have two SPI ports – one with CE0 connected and the other with CE1. The 3-pin header allows me to select the reference voltage for the MCP3008. The blocks along the bottom are screw terminals. See the post Analog Interface for a picture of how this looked when built.
I will probably be pulling this old board out again to experiment with a thermocouple that I just received. I need it for the flame detection on my Home Brewing Automation setup.