139: Saturday 1st May 2010

I have now completed 1000 miles of electric driving and it has been relatively trouble free.
I left the newly glued LEDs to set overnight and then joined all the anodes together with solder. I had soldered a strip of pins onto one end of a ribbon cable that I salvaged from my "computer bits" draw and then stripped the other ends and soldered them to each LED cathode and one wire to the joined up anodes. I then plugged the pin strip into my prototype board, applied the correct resistance and checked they all worked. The orange and yellow ones didn't appear as bright as the red, blue and green. Next I took the LED matrix display off the circuit board and mounted a strip of pin sockets in its place for the ribbon cable to connect to. I gave the circuit a quick test using a potentiometer to provide the input voltage and it worked fine as a curved bar graph on the fuel gauge. Next I put some black tape over the hole where the needle broke off the fuel gauge from when I dropped it. I put insulation tape round the legs of the LEDs and mounted the gauge back into the instrument cluster.

I then mounted the cluster back in the car and connected the circuit. A quick test, then I put the rest of the trim back together. In the photo below you can get an idea of how the gauge will look at night. The photo was really difficult to take as in real life you can see definite dots where the LEDs are. All the LEDs look like the top one in the photo.
If you click on the photo below you can see what it looked like when I used flash on the camera. This gives and idea about how it would look in daylight, but once again in reality it is a lot clearer than in the photo and perfectly acceptable for normal driving. I am not entirely happy with the orange and yellow LEDs, so I am going to swap them for red when I add the other 2 green LEDs. I am keeping the blue because after a quick drive from a half flat battery pack I found that when the blue LED goes out it starts getting a bit sluggish and really needs to go back on charge. I checked the tester on the programmer and this was at about 119v, so that rings true.

So after several weeks experimenting I now have a separate "state of charge" gauge that shows when I lift off the throttle. This is a quirk I am prepared to suffer. I might come back to this at a later date as I am planning a battery monitor for each of the 10 batteries using a text display showing a bar graph for each battery, then I could use the PIC chip to sample the overall voltage when the throttle is released, keep the display showing this level and update it when the throttle is released again, so the gauge will show a steady display. I will consider this a future upgrade. Next is the Ammeter. I just need to order 10 ultra bright 5mm blue LEDs for this then I have all the bits to get it working. I think I will make a start and have the matrix display that I used before until I get the proper LEDs. This time I will have it hanging down by the cluster as hanging out of the air vent was not easy to see.

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