Speedo, ODO and other Gauges

As mentioned earlier in this blog, I have no speedo cable therefore I can not use the original mechanical speedo. One of the many side projects (that most EVers do NOT have to do), is to make a new speedo cluster. The brief is easy - it should show:

• Speed.
• Odometer (distance the car has ever travelled)
• Tripmeter
• State of battery charge
• Instanateous battery current

Fortunately I work in an industry where I have a jump-start on providing these readouts. I guess if I didn't work with this kind of thing I wouldn't have embarked on this little project - but on with the story.
The "smarts" in the dash will provided by the guts of a proto-type of this Control Unit (for the SIMOCO mobile radio). This one is called a 9022, it runs a PIC 18F6627 microprocessor which gives me plenty of Digital inputs, outputs and Analogue inputs.

The other huge advantage of using this as a base is that display drivers have already been written and the development system is already set up and running. It's an area of software projects that I dislike - having to set up new environments and get used to them. While I didn't write the CU software in these products, I was familiar enough with them where my learning curve was quite fast.




The display itself was not big enough for my purposes, but another Control Unit we make (9030) has a much bigger display and uses the same micro (but the circuit board was way too big), so I grabbed the display driver from the 9030 and came up with a single set that runs the 9030 display. (In reality I ended up using the 9030 software and adapted it to the 9022 circuit board.)

The 9022 and the 9030 Control Units.

Here is my prototype - I do not have the backlight connected yet so it's a bit dark under the light I took the photo.

The centre display shown below is about the same height as the width of an iPhone.

I have placed all information on this one display for now, but the final system will have battery and ODO displays on the two 16 x 2 white-on-blue LCD displays either side of this main one. The main display is "transflective" meaning that it can be read in bright sunlight or backlit - essential for the speed indication.

First line is battery current.
Second line is AH consumed from battery. It starts at zero at the moment but when I start using the car and getr used to how much I can use safely, I will rework the software so it show AH remaining.
Lines 3,4, 5 and 6 are speed in km/hr.
Line 7 is distance travelled. This value, trip and AH are all saved when the speed goes from above zero to zero and are also saved each kilometer travelled.
Last line is Trip. Accurate to 10 meters.

I will show how it all fits together into the Vogue orginal speedo housing in the next post.