|
|
|
| basic type | general preference is for a 12V, umbilical, suggested circuit, lamp overdriving also seems like a sensible option |
| interchangeable heads | use connectors for a choice of heads depending on the dive, or for an extra battery pack, or . . . |
|
drop a sachet of silica gel inside the housing / lighthead - to absorb moisture and stop things from condensing and going gammy |
|
| Aluminium |
Minimum 1/4" wall thickness. I’m using 6" OD tube ; which allows enough material after cutting your internal thread. It also allows you to machine an exterior 'step' if you wish to attach the lid by toggle-latches. The latches can sit under the step and be held in place with a standard jubilee clip. This avoids any through-hull holes The best thing to make a cannister from is the barrel and 2 rear end caps from a pneumatic cylinder. If you can find a scrapper somewhere then you are onto a winner. They have grooves, holes and various mounting options which makes fitting it to your kit a piece of cake. Takes the pressure too I also had a quote for a canister made new by a pneumatics manufacturer - £111 for an 80mm bore x 275mm long cylinder barrel and 2 end caps with the ports blanked off. Would be cheaper in quantities but the cheapest way would be to find a pair of scrap 80mm bore cylinders and take the rear end caps off those. They come ready anodised as well, saving you that bother SLA's are bulkier so the 6 cells amount to similar length as 10 x Nimh. Might be possible to produce a standard cannister which would hold either type Cannister will end up long so possibly worth considering a wider, stubby canister and packing cells in banks of 2 or 3 Aluminium tube and blanks: Best to ring round your local non-ferrous stockists and ask for off-cuts- they usually have some and will sometimes let you have them for free, especially if you ask for a root in their scrap bin |
| Delrin / Acetal | engineering plastics as used by Halcyon etc. |
| Glass lens |
several reports of implosion if too thin use borosilicate, tough and heat resistant, 80mm dia piece up for about a tenner - to seal it, the best way is to machine a step into the end of the torch with an O-ring in it so the bigger the pressure, the better the seal. You don't need to thread the end then, just use a stainless or plastic circlip Got the borosilcate glass from a local glass stockist - just ring round to find a suitable supplier for your design. The glass is used for fire fronts and inspection ports so is quite common I used a sealed dichroic and was planning to not have a front glass. No idea what depth a dichroic will collapse at so I was going to take one into Stoney some time and find out - I took one to 35m at Stoney - it didn’t implode, it just let water in - water got in around the front glass on my cheap Homebase lamp - doesn't look like this will work. I think it probably leaked at 1m Glass Precision Engineering www.gpelimited.co.uk |
| Lighthead |
maybe if the light head were made a with a DIN screw, a standard plastic dust cap type design could be used to protect the exposed connections? - ref. disconnecting the lighthead to prevent accidental switch-on Possibly would have to be turned out of solid as tube walls might be too thin to provide lands for O rings modified Maglite ? - sounds costly and complex . . . . purpose made head would be better Maglite (2 x D cell) for £17 - maybe not so costly . . modified cheap dive torch ? Hozelock garden pond light – only £11 from TLC - verified ok to 40m - that’s some pond !! a few alternatives – mostly more expensive but some worth a look: Lunaqua Noma Aico Mariner Acorn Halley Maplin ? |
| Overdrive with high V |
Overdrive the lamp for greater efficiency. Filament lamps provide whiter light and more light per watt at higher filament temperatures - maximum efficiency is reached just below filament melting point. There is a compromise between efficiency and lamp life. Most dichroics are rated for a life expectancy of around 4000 hours - it makes sense to sacrifice some of that life for much better efficiency From Osram’s LV Halogens pdf (link below) the following 'rule of thumb': 05% increase in voltage (from rated voltage) results in: 50% loss of lamp life 15% increase in luminous flux 08% increase in power 03% increase in curent 02% increase in colour temperature I ran some overdriving tests a while back The following table shows measured currents at various voltages and a few life-test results. The R and W values are calculated The lamps were mainly on all the time during test, I just switched them off – allowed to cool – and switched back on a few times a day. Expected life in a torch with more on-off cycles and lots of knocking about would probably be less than shown here Brightness levels were generally very impressive at these higher voltages. The lamps were clearly uncomfortable when the voltage exceeded 21V - getting very hot and giving off some pretty nasty fumes, but seemed ok below 20V. 
* I suspect that my psu went berserk and blew this prematurely – the onboard wobbly Voltmeter was showing 28V when I found the lamp dead. The psu itself died only a couple of hours into the next test . . . . . . Either way, I’m fairly happy that 19.2V is going to be OK and have bought 16 x 7/5AF batteries. I can’t do any more testing anyway and if it proves too much I can just take a cell(s) out of the circuit |
| Dichroic |
cheap, good choice of reflector angle / beam width / power lampholder IRC = Infra-Red Conserving - an energy-efficient lamp construction. A coating on the halogen capsule reflects much of the radiated infra-red energy back onto the filament so reducing the energy requirement to keep the filament at operating temperature. Reports vary from 30-40% savings - sounds optimistic but what do I know . . . . I’ve ordered some Philips Masterline ES to try |
| Philips Masterline ES |
IRC axial filament lamps from Philips: Masterline note: unusually, the glass front on these lamps domes out about 2-3mm, might need to consider this in lighthead design |
| Osram LV Halogens |
Osram lamp data - (4.4Mb but loads of info inc. Xenophot) Describes that Xenophots should not be overdriven – they already operate at higher temperature than standard halogens Osram’s IRC axial filament lamp: Tru-aim general Tru-aim detail |
| GE Lighting |
GE technical catalogue.pdf |
| HID |
Airspeed Press HID Update probably too complicated and risky (expensive) for the amount saved |
| General |
Drawing comparitively large currents from the batteries requires a good connection between the cells, not just touching as in normal torches. Batteries can be got in pre-made sets ie. 6 or 12V with welded connections or buy tagged cells and solder them up yourself To connect your battery pack to the rest of your lamp (inside the canister) use a connector for radio controlled cars- they click shut, so they won't come undone, and can take the amps running through them Stick an in-line fuse into the system to stop everything going pop if there is a short - Will need to be quite a high value time-delay fuse as the normal switch-on surge will be high all sorts of odd batteries available here: www.bullnet.co.uk |
| Sealed lead acid |
bulky, steep discharge curve, but cheap and robust voltage decays so light will dim with time. Characteristic voltage is 2V so need 6 cells to get 12V. A set of 8Ah Cyclons from the CPC catalogue = 6x £8 = £48. Will run a 45 watt bulb at full brightness for approx 1 hour, possibly longer. I have a torch which uses 5Ah Cyclons and it runs a 45W bulb for about 45 mins before it yellows 12V, 5Ah for £48 |
| NiCd |
need care to avoid memory effect, flatter discharge curve to maintain brightness, 1.6Ah D cells from Budget @ £1.70 each nb. according to budget battery info these particular NiCd’s do not suffer from the memory effect 12V, 1.6Ah for £17 |
| NiMH |
powerful, can be expensive but probably a good investment, 2.2Ah
D cells @ £3 each, or 7Ah
D cells from Budget @ £6 each look very good value. Tagged cells are a better option for high currents: 7Ah
tagged D cells @ £8.60 each, or 9Ah
tagged D cells @ £9 each
12V, 2.2Ah for £30 12V, 7Ah for £60 12V, 7Ah for £86 (tagged) 12V, 9Ah for £90 (tagged) 2Ah AA cells from 7DayShop for £5.75 for a 4-pack 12V, 2Ah for £18 (with 2 spare cells) With the new ideas on overdriving I’ve opted for these more compact 3.8Ah 7/5AF cells @ £4 each 19.2V, 3.8Ah for £64 - (they've arrived - they’re actually marked 3.7Ah) |
| Reed and relay |
keep housing penetrations to the minimum relays from Maplin relay1 relay2, reed switch from Maplin reed, magnet from Maplin magnet |
| Toggle switch |
cheap and simple |
| Protection ? |
accidental switch-on prevention idea - an in-water switch as shown here: insel.heim.at/malediven/350052/cibis_e.htm don't mess about with in-water detection, just have a positive lock on the switch for transport or disconnect the light head and shield the exposed connector to avoid shorts |
| Dimmer |
www.cs.indiana.edu Automatic battery protection - if you deep discharge those expensive NiMH batteries too many times then you'll end up buying new ones Low battery warning - gives you a chance to dim it to extend burn time before it's lights out, Sooty Starts the bulb off gently rather than full power straight away.Most bulbs blow when you switch them on - the LVR dims the bulb up stopping this Connection was extremely simple - 2 power wires to the LVR, one feed from the LVR to the lamp head and another from the lamp head to the battery -ve. The LVR comes with a switch pre-mounted which I changed for a magnetic reed switch. The great thing about this switching arrangement is you don't need to have the reed switch permanently energised by a magnet - just press and release the switch for 1 second to turn on/off and quickly press and release to dim. The practical upshot is instead of having a magnet stuck to the torch permanently, I have one attached to my harness (with another spare on the umbilical cable). Wave the magnet over the lamp head for 1 second and it fires up. Wave it over again and it switches off. For £40 you get a bit of kit that does so much - well worth it. They were originally made for Pizel caving head torches so are rugged and very small When ordering, you specify the nominal voltage of the battery pack – mine is 16x1.2V = 19.2V. Runs more like 21V when fully charged. The recommended warning voltage and cut-off voltage will be recommended by them - they are very knowledgeable about this sort of thing and are a great help. They have an example setup for a bicycle headlamp of 100W with a 24V lead acid pack or 19.2V NiCad. |
| External terminals |
removing the need to constantly open and close the battery housing just has to be a good idea - leave it sealed sealing is not possible with SLA's as they gas when charged. NiCd and NiMH only gas when severely overcharged - this would require extreme neglect with the slow-charging system described below but might be a concern with a fast-charging system Use the wet connector as the charging connection and have a small bolt with an O-ring penetrating the cannister to be loosened when charging to release any gas. Good idea - I'll probably do this if I upgrade to a fast-charger For ideas on a self-sealing gas vent, look at some commercial lights such as the tiny UK 2L. It's rated to 500', but has a pinhole covered by an O-ring to allow outgassing. The venting O-ring is separate from the one that makes the case to bezel seal |
| Off the shelf chargers |
www.mahaenergy.co.uk NB. for an effective "fast charging" system, you will need a unit that can deliver a current(A) equivalent to, at least, the capacity(Ah) of your chosen battery pack. This is far beyond the capabilities of most domestic chargers |
| Homebrew slow charger |
I’ve read up on NiCd and NiMH charging - slow charging seems to be the sensible option for both types for several reasons. It’s simple, cheap and there’s no real problem with overcharging. For slow charging you need a bit more than the battery’s rated voltage and a current(A) of no more than 0.1 of the capacity(Ah). At this rate it takes around 15 hours to fully recharge a completely flat battery, a half-discharged battery would recharge in half the time A mains adaptor, modified to provide constant current is probably the simplest, cheapest and safest option. A 15V regulated adaptor should have enough space and a bit of pcb to fit the constant current circuit inside – if you hacksaw the thing open Even though it is ‘safe’ to overcharge at these low currents, a mains timer would be a wise precaution – see time notes with the circuit |
| IP68 spec. |
IP stands for Index of Protection. The rating IPX7 is for 15cm depth for temporary immersion. The rating IPX8 should be qualified with a depth or pressure. For example, there are some glands in RS Components rated at IP68, 5 bar. There are others in RS Components rated at IP68 15bar. Same standard, different qualifier. IPX8 without a qualifier is no better than IPX7 use a "Wetmate” connector . . .. any details ? connectors for 2 miles depths !! NSW Technology in Aberdeen (01224 703595)- anyone got any details ? Use a wet connector in the cable or on the cannister. This would allow quick change of lamp, even under water Bulgin Buccaner Standard tested at 100m www.bulgin.co.uk Subconn connectors www.subconn.com - very nice, and their UK agent www.macartney.com |
| O-rings |
source from washing machine spares shops, bearing stockists etc fit so they are compressed with pressure www.bsl.co.uk www.barnwell.co.uk good technical information on O-rings and their usage at www.americanseal.com |
| Glands |
RS Components IP68 glands confirmed ok to 70m – recommended to drill and tap endplate and fit gland directly |
| Compression fittings |
some reported successes with standard plumbing compression fittings, makes me nervous though |
| Umbilical cable |
HO-7RN three-core 1.5mm pond cable I'm not sure that 'special' cable is necessary, I'll be using 4 or 5 core for flexibility and to allow for some future development, eg. fast charging, dimmer etc |
|
The Divelight Companion |
www.airspeedpress.com |
|
|
Some u/w lighting chat |
www.videouniversity.com |
|
|
Lamps / corrosion |
www.aquabeam.demon.co.uk |
- some general lamp history and notes on disimilar metal corrosion risks |
|
General lighting info |
www.epanorama.net |
- loads of information on every aspect of lighting |
|
Philips Masterline ES Osram LV Halogens GE technical catalogue |
www.lighting.philips.com www.sylvania.com ge technical catalogue.pdf |
|
|
HID info HID Ballast |
www.airspeedpress.com ~wvsp/light1 |
|
|
NiMH info - Ever Ready NiCd info - Ever Ready NiMH / NiCd info - Budget Yuasa SLA batteries |
data.energizer.com data.energizer.com www.budgetbatteries.co.uk www.yuasa-battery.co.uk |
|
| O-ring information |
www.americanseal.com |