Project PITS

RE: Project PITS

three-phase — Sun, 18 Nov 2018 22:21:27 GMT

LibreCAD has come to the rescue. With this I have managed to create an outline of the PCB to maximise the space within the Hammond case. Compared to the other CAD packages I have used, it wasn't the most intuitive, but will a little help from the forum, a couple of hours saw a reasonable result.

A 10uF decoupling capacitor has been added close to the supply pin of the comparator as detailed in the datasheet and recommended by [mention:4f57fc9d538949ad9eb336ddb9469bb8:e9ed411860ed4f2ba0265705b8793d05].

I also put a cutout in the PCB where I aim to fit the single 18650 cell. I have obtained some Keystone 590 battery clips that will provide the connection from the PCB onto the cell. I am yet to create the footprint for these for the PCB, so they currently aren't on board.

[View:/resized-image/__size/171x218/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-a7b3411c-7fe2-4b98-88c8-af9d83895613/7103.contentimage_5F00_189157.png:171:218]

The circuit has been updated to include a latching circuit courtesy of EEVblog #262 or on youtube. This circuit is untested, I had ordered the parts, but UPS seemed to only deliver half the order last week and left the rest in transit, better luck this week.

I have left an area at each end of the PCB unpopulated so that I can install the connectors at one end and the battery charger and boost circuit board at the other. However, I feel the the soft latch circuit should come between the battery charger and the boost circuit to allow the unit to be charged whilst switched off. This means, I will not be able to use the pre-built board, so I am now looking at building the circuits onto the PCB using the MC34063A for the boost circuit and the MCP73831 for the charging circuit.

Updated PCB - needs battery clips adding, but the shape is good;

[View:/resized-image/__size/620x358/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-a7b3411c-7fe2-4b98-88c8-af9d83895613/1222.contentimage_5F00_189158.png:620:358]

Updated schematic;

[View:/resized-image/__size/620x426/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-a7b3411c-7fe2-4b98-88c8-af9d83895613/7178.contentimage_5F00_189159.png:620:426]

Kind regards.

RE: Project PITS

shabaz — Wed, 14 Nov 2018 16:03:01 GMT

Hi Donald,

Very interesting project! It has uses beyond your scenario too - there could be many instances where legacy machines with indicators need to be integrated into some system.

Excellent project, and it seems to work really well! Those handheld enclosures are really cool - I used a similar one for a tachometer project a while back.

RE: Project PITS

genebren — Tue, 13 Nov 2018 22:47:42 GMT

Donald,

I really like the cleverness of your design (especially the magnetic holders for the photodiode). I looks like you have worked out (with the help of some community members, yeah!) a lot of the issues and/or problems.

Well done!

Gene

RE: Project PITS

14rhb — Tue, 13 Nov 2018 20:13:33 GMT

Donald,

You are a genius, this is a great project (and well written up ). I'm assuming you are an electrical engineer by trade (I cannot imagine anyone would start looking at measuring the accuracy of the MCGG units otherwise). This may be of interest to anyone who requires monitoring an LED but for safety reasons or voiding warranty would perhaps prefer not to open the enclosure. I wondered how you were going to hold the probe on until I watched your video - a great solution to use a magnet.

Rod