Uri Baran's HUD
"Always know your PO2!"

Uri Baran’s Primary HUD display Unit

This is a generic HUD unit for PO2 monitoring and as such could be fitted with a little modification to any rebreather. The unit is designed as a fail safe module which keepsall 3 channels completely independent except for the battery (which fails safe) so the unit can be trusted. The unit is designed as a monitoring unit only and not a controller

The nice features are a separate (optional) Buddy light (shares one of the channels) which you can mount where ever you like and a neat HUD unit that contains 6 LED’s, (1 red and 1 green for each channel).  A VR3 connector
option is also available to connect to one of the existing cells. The controller unit is proofed and tested to 120m (production unit depth spec may differ) and in an inspiration can easily fit on the base of the scrubber stack. The only control is a calibrate button which is pressed when the loop is at 100%, i.e. while you’re calibrating the Inspiration and the “Calibrating” screen shows

The unit would need an extra through scrubber fitting added for the Inspiration and then some Y molex’s  need to be inserted between cells and Inspiration electronics.  Uri’s unit is just provided with a Fischer terminated lead for cell connections
 
That’s it. The rechargeable control unit is sealed and potted to prevent leaks. Battery voltage is checked at start up and continuously throughout operation

The LED’s flash pattern allows you to monitor your PO2 and recognise if it’s above or below your desired range


The design aim was to only alert the diver if there is a problem and so use solid green led signals for normal  operating modes so there would be no irritating flashes except when there needed to be.
A sequence like this is shown below. This is for Inspiration like setpoint controllers. Each cell is represented by a pair of red/green leds.

Pp02 LED Sequence

1.6 and above RED
1.6 - 1.45 RED to GREEN. slow flash.
1.15 - 1.45 GREEN
0.8 - 1.15 GREEN ON/OFF slow flash
0.6 - 0.8 GREEN with flicker
0.45 - 0.6 RED to GREEN. fast flash
0.05 - 0.45 RED flash on/off fast
<0.05 Led off

Other rebreathers would need a different sequence because they have different setpoints. There is also the issue of whether to have a standard display sequence or make the sequence something the user can choose. For instance, people may choose to fly their units below their standard setpoint in which case, should the sequence be adjusted such that the new setpoint is represented by green leds which are on or some other signal? Let me or Uri Know your thoughts on this
 
The unit can be programmed for individual needs.
 

Pro’s
Retrofittable on most rebreathers
Reliable, independent electronics designed for failsafe operation
HUD as primary monitor saves having to watch handsets all the time
Buddy light option
VR3 connection option
Increases safety
Rechargeable

Con’s
Cost (initial guesstimate around £600)
Have to make extra fitting hole in Scrubber lid
Something else to recharge
Warranty? This will almost certainly invalidate your warranty

Uri’s attention to design and manufacture has meant that he has been able to apply for a Patent on the unit based on the multiple redundancy and failsafe nature of his design and he has written confirmation by the powers that be that this Monitor does not require CE to be sold in Europe, so the homework has certainly be done here.

The unit has not quite reached the final production stage yet, but the prototype appears to work very well

This HUD monitor would be a good safety addition to a rebreather. The hands free and always visible nature of a HUD, means that even if your forget to check your handsets you should be warned of dangerous situations developing and the failsafe design of the unit means you can trust what its telling you.

For more details please contact Uri on uri.b@virgin.net