Ch-ch-ch-ch-Changes (in some parts)

A project log for Universal Glucometer

Did your test strips just get more expensive? Has the drug store run out of strips for YOUR meter? Like to be able to use any test strip?

Tom MeehanTom Meehan 09/14/2016 at 04:460 Comments

ARRGH... of course I forgot to order 1 part, in this case it was the surface mount power connector from the battery pack to the board. I choose this connector because the female side is used on lots of lithium single cell batteries and other battery packs (so I figured that the receptacle must be pretty common also... and my goal is to use an easy to source parts). Additionally, the Eagle CAD part is available in the Adafruit part library (so I wouldn't need to go through the headache of making a new part in Eagle). As it turned out, I could only find this part at Sparkfun (JST Right Angle Connector – White PRT-08612) or Adafruit (JST-PH 2-Pin SMT Right Angle Connector PRODUCT ID: 1769) and no where else – not Digikey, Mouser, Newark or even eBay. Well, that didn't equal common or easy to source part for me.

Looking for a solution, since my boards are already out for fabrication, I needed to find something. Of course I could always just solder the battery pack leads directly to the board but I didn't want to do that. Eventually I found that the through hole version, which is quite available (either as the JST-PH-2 or Molex 5264), can be altered to fit the footprint for the SMD version. Both of these, the female connector and the male through hole receptacle, are fairly common as battery cable connectors in old wireless phones, lantern battery connector, older computer boards and many other devices (which is where I found the ones I'm now using). As soon as I can get the new part numbers I'll put them in the Bill of Materials, until then I'll leave the surface mount version.

By bending the through hole wire connections back 90 degrees (so they are in line with the connector and extend out behind) they actually match the surface mount dimensions (yeah, this is definitely a Hack but there is no way I was going to place an order for just one part when postage and handling is more than the part itself.

Soon after placing my last parts order I worried about the clearance for the Reset Switch that is placed in the top right of the PCB (which is under the LCD screen), I thought the switch might be to tall. After I received my order I used the actual parts to check clearances... and I was correct, the switch was to tall. Looking through my scrap/salvage boards (from old appliances: TV's, VCR's, Computers, Toys, etc.) I found some lower profile tactile switches with the same footprint as the ones I ordered. Beware – the current part number for this switch, on my Bill Of Materials, is the old switch since I need to find a part number for the lower profile one (as soon as I do I'll change it on the BOM – with a comment).

Here, you can see the difference:

I'm close to having all the base code straightened out and I'm designing the case for 3D Printing using OnShape. My project file is Public (so anyone with an account, which is free, can look at it - or download it) and it is named UniversalGlucometerCase. So, you can check out my design progress if you want.