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-   -   laser fluid detector. (

dcb 04-26-2008 04:51 AM

laser fluid detector.
Here is the setup: A 5v power supply, a laser, a 5/16 tube with a gasoline sample in it, a cds cell, and an ohmmeter. The tube is flat against the board and the laser had to be propped up a tiny bit in front to hit the CDS cell through the empty tube.

The tube is empty in front of the laser and the CDS cell is well illuminated.
It is about 1.5K ohms here:

The board is tilted and the laser gets deflected by the fluid in the tube and misses the CDS cell.
It is about 11K ohms here:

So there ya have it. One just needs to carefully drill a couple holes in a block of wood to organize this assembly. But with a jump from 1.5k ohms to 11k ohms it should be pretty easy to detect.

Here is a cheesey picture of what is going on. Note that you have to adjust for the empty tube when aligning the laser, it does not just go straight through! Also, the farther away the CDS cell is from the tube, the greater the deflection distance.

MetroMPG 04-26-2008 07:40 AM

Building a better "low fuel" idiot light? :)

dcb 04-26-2008 10:22 AM

Actually that would be nice to have on a motorcycle. It would be much better than waiting for the engine to start cutting out in the middle of an intersection to remind you to switch to the reserve tank :)

Though my priority with it is a motorcycle fuel consumption monitoring system, I'd love to hear any other ideas how this could be used.

MetroMPG 04-26-2008 10:52 AM

Ah! I forgot about the old reserve valve! Been a few years since I had the Ninja 250. :D

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