Current card revision

ngadiyar93 commented 4 years ago

This PR addresses issue #11

Background

The voltage reference REF5050 (U3A) on the current card requires the input voltage be 0.2V greater than the output voltage V_REF. That is, for a V_REF = 5V, the input needs to be at least 5.2V, which was not the case and needed fixing.

Scope of the PR

This PR does the following

V_REF reduced from 5V to 4.5V.
New part selected for (U3A) - REF5045 pin compatible with earlier part REF5050
Resistor values in the level shifting stage of the signal chain updated to work with the new V_REF and get a 0.2V-4.5V range at the ADC input terminals.
Documentation added

Changes in the input / output

From a card user's perspective, there is only one major change in this revision - The output of the level shifting stage is now 0.2V-4.5V. It was 0.2V to 4.8V earlier. There is no other change expected.

Note: There are no layout and footprint changes.

ngadiyar93 commented 4 years ago

Added current card documentation

ngadiyar93 commented 4 years ago

Very nice work, @ngadiyar93. A few comments:

In your main docs README, in the design requirements 5, you state the board connects to the AMDC over SPI. This is not true: it connects to the motherboard over SPI.

Excellent documentation! Very clear and easy-to-read. However, can you add a bit of detail to the ADC section, namely, what voltage are the ADC input pins connected across? Is the + pin the main signal and - go to GND? At 0 current input, what voltage is expected at the ADC terminals? How would someone compute the A/V gain of the sense circuitry (or perhaps you can just provide it)? What is the expected A/V gain using nominal parts? Each section of the circuitry is not critical to list A/V gain, but overall A/V is needed (i.e. for 1 turn of wire flowing 1A DC, what voltage is measured).

Let's mention what size resistor footprint is used for the "common" parts that could be swapped out => i.e. the burden resistor and the LPF parts. Give some discussion as to when someone might want to change these values. For example, if I am trying to sense a 5Apk-pk signal, should I use this board? I think the answer is yes (with multiple turns of sense wire), but seeing the range is +/- 55A might be very confusing for someone since that is very large.

Please make the background of your schematic sheet pure white, it is currently an off-white hue.

@npetersen2 I have addressed your comments. Could you please take a look and provide feedback?

ngadiyar93 commented 4 years ago

Reopening - closed by mistake :/

ngadiyar93 commented 4 years ago

@ngadiyar93 Changes look good, but a few spelling issues are present.

Please run the .md files through a spell check and fix the issues, then I'll approve!

@npetersen2 I just ran the spell check and fixed the issues in the .md file.

ngadiyar93 commented 4 years ago

@ngadiyar93, I agree with @npetersen2 that you have done a very nice job with your documentation.

We do still need you to implement changes to make REV20200830C compliant with our expected folder contents for a release described here. Here is an example of a release folder.

Missing from this release folder:
* Markdown or CSV BOM

* README.md describing how to order

* the gerber files in non-zip file form
Finally, when we merge this, let's remember to do a squash and merge to prevent the repo from growing too large due to revisions of binary files.

@elsevers Thank you.

I have added the gerber files in the non zip format. Do you want me to delete the zip file? or should that also reside?
I have added the BOM in the .csv format
I am not exactly sure of the ordering instructions (I haven't ordered any of these boards before). So do you think that may be something to add once I order this? OR should I simply adapt the instructions here

ngadiyar93 commented 4 years ago

[x] Remove the zip file of gerbers

[x] It seems like there are a lot of gerber files here relative to other projects. Are some of these files unnecessary?

[x] Add a README.md with info on how to order. You are planning to order these for your project, so figure out the necessary info you should provide in these tables to place the order. The link you provide seems like a good template to follow. Otherwise, you can keep it simple and stick to the basic PCB properties as is done in this doc.

Some of the Gerber files seemed unnecessary per this link - they weren't listed there. I have removed such files.

ngadiyar93 commented 4 years ago

[x] Remove the zip file of gerbers

[x] It seems like there are a lot of gerber files here relative to other projects. Are some of these files unnecessary?

[x] Add a README.md with info on how to order. You are planning to order these for your project, so figure out the necessary info you should provide in these tables to place the order. The link you provide seems like a good template to follow. Otherwise, you can keep it simple and stick to the basic PCB properties as is done in this doc.

@elsevers I have made the updates. I am assuming that we are ordering the PCBs unpopulated because they are quite simple ones which we can populate ourselves. So, the data I have in the README.md is closer to the basic PCB data here.

I did a dry run trying to order the PCB from a vendor (OSHPark) to make sure this info sufficed.

Severson-Group / AMDS