Idea: Devise a simple plug in meter that will work on any OBDII equipped vehicles.
While doing research I found that standard OBDII pinout will give you battery voltage on Pin 16 and a chassis ground on Pin 4. I started with a WM3476-ND housing and WM3455CT-ND male pins that would connect to the housing in my car.
For a voltmeter I selected the 1597-1236-ND from Seeed Technology. This meter will read voltages from 2.6-30VDC and is in a small 30/11.7mm screen size.
![image](https://global.discourse-cdn.com/digikey/original/2X/5/52aa1dadfc0188cf33019a4744a6ccb80e902a1a.jpg)
To ensure there was no issues cause by my circuit I also added an inline fuse F2308-ND.
I then took measurements of my different components and using free online software from OnShape I was able to create a housing for the voltmeter project. This housing was then printed on a Prusa 3D printer. Using the scheme it app from Digi-Key Corporation I was able to diagram the simple circuit.
![image](https://global.discourse-cdn.com/digikey/original/2X/b/bf1e4b1dc3495b9ef8dc7f1f2bdb559a27a5ebd3.jpg)
![image](https://global.discourse-cdn.com/digikey/original/2X/3/3b1e441e31c0e11c910b71e86e36a42c0f213afe.jpg)
The initial unit was assembled and it was requested that I add an on/off switch so that the unit could be left in a vehicle and no voltage would be drawn. With a slight change to the schematic I added switch CH865-ND.
I then also created a new housing to accommodate the switch.
![image](https://global.discourse-cdn.com/digikey/original/2X/f/f9571628b17dd097654ccfda47639b53c99c637f.jpg)
![image](https://global.discourse-cdn.com/digikey/original/2X/e/e2aabbd0dd841c596569db920641aa97c32c26ae.jpg)
The housing was then printed and assembled. The working prototype is now functional.
![image](https://global.discourse-cdn.com/digikey/original/2X/4/4e2d6c82567a960e65ba596392a487fcc5357c76.jpg)
![image](https://global.discourse-cdn.com/digikey/original/2X/7/7007dc4389b9036ca8dd14ea86b9bc3895484069.jpg)
Click Here for the OnShape link if you are interested in printing this part.