Coolant mixture sensor (psuedo-refractometer)

March 15th, 2010 | Categories: Electronics | Tags: , , , ,

A bit ago I got the idea of trying to determine the mixture of coolant vs. water by detecting both light occlusion of the mixture and the wavelengths blocked / passed. This initial device is just a rough prototype that will assist me in determining a course of action in regards to overall design.
The idea behind the device is to have the sensor fitted on to any pipe attached to the machine where coolant goes through and give a live measurement of coolant mix and alert the operator if the mix gets too high or low. Also I’d like it to detect tramp oils that have been beaten in to the coolant.

Coolant meter board

The board itself is pretty simple, just a PIC16f690 hooked up to an rs232 driver and using three analog channels. I may in the future build a more sophisticated ADC board, but for now, this will do. The mcu is linked to the two rail to rail opamps, 7014D’s to be exact. they were needed to condition the signal from the LEDs.

Coolant meter test receptacle

The sensor area is basically a cup with a white LED as a light source for the sensor LEDs. The three LEDs are IR, Orange-red, and Green. The LED’s respond to wavelengths more energetic than the ones they emit, therefore, the selections I made. I did try a blue LED but the response wasn’t good at all. Hopefully it will provide useful data, hopefully.

Coolant meter terminal output

In order to make data easier to collect, I put rs232 communications on it. I can store and track data this way. Above is some of the terminal output. Notice that I’m taking 10000 samples… this has the effect of increasing, to a very limited degree, the resolution of the device. It is however fraught with error thus far…
Anyways, any data collected and the design of this is extremely preliminary. I’m not even sure it’s a valid or useful idea yet.
As an extra bonus, or punishment, here’s a video I made for this device.

  1. ibis
    February 2nd, 2011 at 02:10
    Reply | Quote | #1

    Did you ever get this thing working? This is a cool idea!

  2. smackaay
    March 2nd, 2011 at 17:13
    Reply | Quote | #2

    No, to be honest. I have figured out some other ways of doing this project, however fouling of the sensor remained the problem on this idea. I did try some surface coatings but the result was the same, just slower. 🙁

  3. Alex
    May 19th, 2011 at 08:51
    Reply | Quote | #3

    Would you mind sharing some of your “other ways”? Very interested in this topic.

  4. smackaay
    May 19th, 2011 at 09:17
    Reply | Quote | #4

    Yes, some of the other ways include:

    Basically pushing the coolant through an orifice and having the coolant be exposed on the way down through the orifice to be recollected later at the bottom of an enclosed tank. this allows the fluid to be measured without fouling of a surface of some kind. Using a laser or focused beam of light, you can determine the mixture.

    Also, there’s the vibratory method that I played with. It doesn’t tell you everything but it can measure thickness of the fluid and sort-of tell you how much tramp oil there is with frequency modulation and response.

You must be logged in to post a comment.