If you were to design the perfect bottom timer...

[lowviz]

...//... I don't think data logging for this kind of thing is worth the cost/complication of IRDA or bluetooth or even a port, but maybe I'm overestimating the cost/complication. ...//...

I always like to plot my dive profile, especially the ascents and descents. I dive a VR3, but like Uwatec's IRDA interface much better. He did say the 'perfect' BT, just dreaming...

 

[Pinkyfoool]

We would need a easily resettable average depth and time on the main screen.

 

[TSandM]

Under $100? Hmm.

I don't care how much cumulative time it logs; I want it to log dives until I clear it or download it (prefer downloading). A dive being defined as the period from submerging to return to the surface, no matter how long that period is. Holding 20 dives would probably be fine -- it would certainly make me more diligent about downloading!

I'd like depth, time, and to be able to get a readout of average depth.

I'd like a simple method for recharging, or a battery life measured in months, if not rechargeable.

I want it to fit in a DSS boot. I cordially loathe straps of all kinds.

 

[KeithG]

Many people go on dive vacation trips. Being able to retain the complete trip worth of data would be useful (no need to carry downloading equipment). Also useful for forensic purposes if something bad happens. If you are doing lots of dives, you will still retain some nitrogen loading the next day. So you really want the complete trip worth of data to be available.

So a minimum of 2 weeks of diving would be good. Not sure how many minutes this is. But a minimum of 50 hours would be a starting place. More is better. Memory is almost free these days, so put lots in.

Also agree with the suggestion of wet contacts and water (not pressure) activation Instead of buttons (like early uwatec computers). Also consider filling it with oil so the case does not need to be so strong (again, like early uwatec computers).

Or if it is designed to discardable at the end of battery life, then just pot the whole thing as a solid mass. No moving parts (other than the pressure sensor) no serviceable parts, no need to design a case that can be opened for service. The potting compound can be the case.

---------- Post added July 3rd, 2014 at 05:47 PM ----------

going cheap likely means no rechargeable battery circuitry. Going real cheap likely means no user replaceable battery either. Setup cost to design complex case moulding and then include a watertight door can be significant.

This may mean a larger footprint in order to include sufficient battery power so that it becomes a disposable unit.

So I want a battery life of around 500 1 hour dives with at least a 5 (or 10) year shelf life.

 

[Akimbo]

The world doesn’t need another proprietary hardwire or wireless technology. If you are going to provide a download function, please make it Bluetooth rather than any other wireless technology. However, the downloading functionality might exceed your objective for bare bones and simple.

One thought to avoid accidental user resets during a dive is to provide an external magnet that stays on deck… or a Bluetooth interface to a smart phone or computer if you have it.

I would have it auto-wakeup from a water sensor. In an ideal world, the user could choose the “start timer” depth themselves just to get the manufacturer out of the line of fire since that can be a point of contention. Allow selecting units by smart phone as well if you go that way.

 

[KeithG]

We can all learn from the past (and since I brought up some uwatec ideas) I also just remembered about the small round (about 1 1/4 inch) pressure activated digital bottom timer that Sherwood provided in console clusters back in the mid 80s. The device only displayed bottom time and dive number on an LCD screen. So it had some smarts, but not much. No pressure sensor.

It was activated via a fairly simple mechanical pressure switch that closed a contact.

Mine stopped working sometime in the mid 90's and I just discovered a few years ago that it had user replaceable batteries. I thought it was disposable. It now has a fresh set of button batteries and works like a charm.

---------- Post added July 3rd, 2014 at 07:03 PM ----------

One thought to avoid accidental user resets during a dive is to provide an external magnet that stays on deck… or a Bluetooth interface to a smart phone or computer if you have it.

is a reset even required? I can not think of one (but maybe that is because i don't know something) Maybe some one can provide a situation where a reset is needed?
every feature you add, increases the cost.

Seems like we are starting to discuss a perfect $100 Ferrari.

 

[lowviz]

...///... Seems like we are starting to discuss a perfect $100 Ferrari.

-Most amusing, nearly perfect example of an engineering cycle.

Start with the rank basics, everyone gets infected with functionitis, then marketing comes up with a ship date, back to basics and one or two really good ideas that will just make it in time.

Somebody has a totally killer "senior project".

 

[Centrals]

Old Uwatec bt with user replaceable battery. Done

I prefer the newer model ie. with average depth.
YES, user replaceable battery is a MUST.

 

[kr2y5]

Would it need to tell you how deep you are currently? Max you've been? Do you even want this information, or would you only want something that keeps track of time?

You can get a stopwatch rated to 150 feet for about $15 at Walmart, it would be hard to beat that price... I would rather hope to see someone go in the opposite direction, and reinvent the SPG by cramming electronic pressure and depth sensors and a timer in a package the size of a regular SPG... basically, something like Suunto Cobra, but without the "computer" functionality, memory and other superfluous features, in a smaller package, and at a lower price point. If one could believe it is rugged and reliable enough to replace the SPG, served dual purpose as a backup bottom timer, and cost less than $200, I think it could be wildly popular.

 

[ajduplessis]

Shearwater Petrel (gauge mode) in a 50% smaller package (flatter profile). The perfect BT!!