Wednesday, October 22, 2008

The speedometer.

Now, it's time to discuss the instrument console. Due to automotive regulations, every motorcycle needs a back lit speedometer. I wanted a complete speedometer meter kit which included a pickup mechanism. Although there were several analog meter kits I could have used, I thought a digital look would be best for the BugE.

So, browsing the web, I found a complete meter kit at It included the meter and also the pickup mechanism. Originally, I ordered the simple XR-SA meter on the left that had a speedometer, odometer & some bonus indicator lights. It was simple and probably would have done the job just fine. For a battery volt meter, I figured I would use the analog meter for now and then switch to a nicer looking bar graph unit at a later time.

When my meter arrived, for whatever reason, I got the nicer rx-srn meter shipped to me instead of the lower cost meter! It's a really nice looking meter. However, it has an extra feature I didn't need - a fuel gauge on the left side of the display!

It seemed too bad to install a retro looking charge meter from EV parts when I now had such a fine looking bar graph included in the digital unit. Surely, I thought, there must be a way of calibrating that slick looking gasoline bar graph so it would show battery charge instead. Unfortunately, such meters work in totally different ways so I would need a conversion circuit.

So, basically, I need to build or find a circuit that can convert a voltage range from a low charge state of say 45v* to a high charge state of 49V* to be a current flow which would mimic a sender unit current flow for the E-F gauge. This is a tricky circuit for me so I've decided to stick with a temporarily mounted analog gauge for now. Later, when the BugE is on the road, I'll be returning to this feature.
(*Voltage levels may be different)

Other than the unused fuel gauge, it is overall a fine looking speedometer kit. It has wires to allow connection to indicator lights such as brake, hi-beam & turn signals too. It comes complete with a magnetic pickup and even little button magnets to put in the wheels! The meter is programmable and the instructions show show how to set the meter for non-standard wheel sizes if needed. It also comes with a mounting arrangement that allows handlebar or dashboard mounting. (I'll be trying the handlebar mount first)

The speedometer also has some indicator lights can monitor what the real lights should be doing. I'll be using a multi-pin Molex connector on the wire bundle so the speedometer wiring can be quickly detached from the cowl wiring should the cowl need to be removed from the chassis for servicing.

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