Sensor and Battery Connectors

Close up of Sensor and Battery Connectors.

Note how the sensor connector passes over battery connection.  The sensor is the last part to be connected to the circuit, and the first component to be disconnected from the circuit.

An important note from page 38 of  Forrest Mimms/Timer, Op Amp & Optoelectric Circuits & Projects (book # 62-5032) concerning Powering Op-Amps states:   "Never apply an input signal when the power supply is switched off."

 In this circuit I have taken that advice,  blindly for lack of other qualifying information, and because I have damaged some Integrated Circuits during this development process.  The HDD Module is designed  such that the Oxygen Sensor which generates the input signal (voltage)  can only be connected to the circuit after the battery is connected.   Likewise it needs to be removed from the circuit before the battery is disconnected.

The Heads Down Display in Operation and Observations

The HDD in the FEOR Light,  Pre and Post Dive.
(Note condensation formation in inside of scrubber canister post dive.)

    The HDD worked.  As you see from some of the post dive images of the unit, condensation forms on the inside of the canister.  If your scrubber is not clear, you may not be aware of this fact.  My electronics pod is in an ambient, and what is considered a condensing environment. (Yes, it should be potted or some other way isolated.  That will come later, see below.)

    Diving with displays within the canister, where condensation has formed,  I have discovered that it is easier for me to detect the color of the LED's better than it is to read numbers on the digital LED Display.  I like this feature.  The information delivered by the colors were received and acknowledged even before my eye was able to focus on the display, which means that the information can be used even if it out of your direct field of vision.  (This can imply that you may never have to actually look directly at a display to use the information it conveys.  LED's could be placed on the periphery of your field of vision, on masks or within helmets.  (The purposeful monitoring of discrete digital/analog information can be a secondary action when necessary.)

    Another subjective observation is that it seems that it seems to takes less time to determine what corrective action needs to be taken using a Color (LED) as a reference than it takes reading numbers from the digital Display.   If I see Green, all "should be" OK, no action necessary.  Only if I see Red, or a Yellow by itself there something that needs to be done.   If  only Yellow, than add Oxygen.   If  Red is noted,  then "Stop" and figure out what is going on.   While using the digital display,  it seems that mental processing involved first reading the numbers, second deciding if the PPO2 displayed was where it should be, if not than next decide what,  if anything needs to be done,  and finally taking the corrective action.   This appears like more steps overall.
 

"CEDU Glass"  our first "Potting" job.

Potted electronics in HDD Sensor Module.

Close up of "Optically Clear and Magnifying" surface.
                                    (And wide angle of optically blurry post test dive picture.)

    The HDD was finally "Potted" within a clear plastic material currently called "CEDU Glass", (a proprietary formulation and process) using a vacuum, pressure and temperature controlled manufacturing system.  Yes, this first attempt is somewhat crude, but it worked. Optical clarity and magnification was accomplished.   (Please note the absence of  manufacturers marks.  In certain circles we must be able to deny that the CEDU had anything to do with this piece of technology!  But for the right price we can put any name, logo or trademark that you request.  Contact the engineering department for details and rates.)

    A test dive of the potted circuit was conducted on 7/14/02 at Cardiac Hill, Palos Verdes a few miles from Malaga Cove.

    Results uneventful. Everything seemed to work, no leaks. The vis was poor and the surge was heavy.  Not a fun dive, except for the fact that the water temperature was warm, about 67 degrees, and I had a nice swim after the dive.  This dive was conducted in swim trunks only, thus it was mo'easy to see the display because my range of  (head) motion was greater. (No neoprene hood to restrict it.).
 

Some other little experiences..
A battery terminal on a 9 volt battery broke off.  (Manufacturing flaw? Luck of the draw?)
A battery terminal clip on the battery connection loosened up resulting in an occasional open condition when rattled, even after a pronounced "snap" when attached to the battery.  (Guess they loosen up with use,  I found you can pinch them in a little and they hold tighter..)
 
 

[ Back to Main Page ]