HUD Project Update

Scuba_Vixen

Hi Guys,

The HUD project is moving along nicely. It seems to get a bit better developed as it progresses.

For those that are new or haven't followed, here's a brief chronology:

The idea of multi-cell PO2 monitoring (exclusive of the HS Explorer and it's cell) started with Narked@90's 3 cell holder that fits in a P-Port.

Before he posted a pic of that little creation, I had a single cell HSE PO2 meter and another cell with the Explorer.

Originally, I planned to use the LTC1298 dual channel AD converter monitoring 2 cells for the hud display, and the third cell cabled thru to my PO2 meter.

Then I figured monitoring all 3 cells, instead of 2, with a HUD would be 50% better. ...... So I went to the Microchip MPC3402 ADC .. Which is a 4 channel device.

I thought about going to a HSE 3cell PO2 meter, but having only one readout and having to wait 'till each cell scrolls past, didn't excite me at all.

So I figured, "Why not put my own digital PO2 readout, right in the HUD controller box!" So I made up a PC board for 3 LCD readouts. (same ones Mark Munroe uses)

All 3 cells drive the readout and the HUD, but each is powered seperately. If the battery or circuitry for the readout fail, the HUD is not effected, and vice versa.

As mentioned, the power for the HUD controller and it's display leds, comes from a seperate 9v battery than the LCD readouts. There are also seperate regulators for the leds, and the microcontroller and op amp circuits. The microcontroller is further isolated from the leds, as it drives them via a darlington array chip. Anything that happens to the cables, doesn't hurt the circuit components.

Here's a pic of everything operating nicely off the 9v batteries. You can see the cells, displays, power board, controller circuitry (on the proto board), and the HUD display. The cells will have another cable just like the one that goes to the HUD. Both will use a connection at the housing, as opposed to cable glands.

I'm now waiting on another cable and recepticle for the cells, (I decided not to use the original one I got), and some reed switches and magnets. After I figure out what'll work there, I can make any final tweaks on the circuit boards, and start making the housing.

Overall, I'm pretty excited about it.


Darlene

Attached Images

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mverick

Nice....

Soon we'll be buying electronics from you..

LS_DK

Hi Darlene,

Looks very nice..

What material and material thickness have you used for the HUD tube ?
I guess from looking at the picture the tube is isolated from the ambient pressure of the loop, and is air filled .. Is that correct ?

Cheers,
Lasse

Scuba_Vixen

The tube is 3/4" diameter polycarbonate rod.
The cable gland is a PG-7 thread size, which works with 1/2"-20 threading. The tube is drilled with the tap drill size for the 1/2-20 thread, (29/64")

I was able to fit regular T-1 3/4 (5mm) leds on a strip of circuit board into that hole. It's then filled with clear epoxy potting compound.

Generally speaking, I prefer 1 Ata over ambient, especially where electronic components are involved.



Darlene

LS_DK

aahhh ok..
It looked air filled..
Cool stuf...

Yes, 1 ATA is prefered..

Cheers,
kasse

Crazyduck

Darlene,
It looks very good!


Any thoughts to the housing for the circuit board or the displays? Do you plan on having the Po2 displays wrist top or a mounted display?

Thank you for sharing.

Andrew

__________________
Howdy Senor- What’s Happening!
Rob Davie April 2005-

Presently in a state of transition from Open Circuit to Closed Circuit.

"You will not be punished for your anger; you will be punished by it." - Buddha.

zbskii

What about a hud that drives three three digit seven segment led displays? There are some that are quite small (7mm) and are tri-color. There'd be no learning of flashing codes, it could simply display all three pp02s, red if below the setpoint, green if on, and orange if above.

Scuba_Vixen

I'm planning to use a block of delrin, (appropriately milled out) and a polycarbonate top.

I'm really limited with what's available, being here on a small island, so I have to work with what I can get from McMaster Carr a lot of the time.

Tentatively, I'll be working with a 4" wide block, that's 12" long and 1.75" thick. I expect to have enough material for 2 housings. The top will be 3/8" clear polycarbonate secured with 8-32 screws around the perimeter and an o ring. I'm planning to leave the sides and bottom thickness at about 0.400" (10mm).

The digital displays will be in the housing. Everything turns on by removing a magnet outside the case. Replacing the magnet turns it off. The backlight for the readouts requires a magnet to enable.

One cable from the cell holder will connect to the controller with a 4 pin connector, and the second cable from the HUD display connects with a 5 pin connector. Trying to keep it neat and tidy.....

Now that everything is working perfectly, I'll be working on the circuit board for the controller itself. The material for the housing should be in next week or so.

I'll post some pics of the controller CB when it's done.


Darlene

Scuba_Vixen

One of the main issues you have to factor in, is wire size and conductor count. It has to be very flexible wire, or it's going to be horribly nasty on your jaws from a fatigue standpoint. If your jaw aches after a few minutes, the display is useless, no matter how cool it is otherwise.

Except to see it, you have to feel like it's not there.



Darlene

zbskii

How many wires do you have now? It could be done easily by sticking a seven segment driver chip in the hud and only a pair of wires for each display. Or perhaps one three digit display that scrolled the values of the three sensors. Just a thought as this gets rid of any need for voting or averaging.