Monday, 12 November 2012

Dive Light - Part #5 - Electronics

The Drop-in has a two mode driver, on and off, to control it underwater I used a reed switch and magnet arrangement shown below. The reed switch can't handle the current draw ( 1.6A @ 8.4v) ) from the LEDs so you need something a little more capable i.e the FET. Here is the Eagle schematic.

2k resistor.

The FET I used is an IRF 540N.

I ordered it from Conrad UK... they also have an outlet on ebay.

The reed switches were also off ebay, these are SPST glass ones.

The plastic block connector has been trimmed down to fit more easily into the case.

The FET had its pins gently stretched and bent to fit across the block connector.

My old electronics teacher would not be impressed with this construction ;)

It was further covered with electrical tape and the reed switch placed against the wall of the maglite so an external magnet would trigger the circuit.

As the reed switch needs a magnet to be placed within range to keep the light on, I needed an arrangement to move the magnet in and out of range without loosing it underwater! My solution was to use a rigid tube which goes round the maglite body... which can rotate with the magnet attached.

Luckily, a bit of waste pipe was just near enough the diameter to fit round the maglite, it wouldn't fit unless a lateral cut was made though.

Cut off about 2cm to make the rotating ring.

To keep the ring tight against the magite, I found some drysuit tape ( but this could easily be inner tube), from this I made a loop using black witch glue. Also gluing a magnet to the rubber loop.

The magnet used was from dealextreme, product description : Super Strong Rare-Earth RE Magnets (20-Pack 12mm x 1mm)

So, to turn on and off the light, just twist the ring. Its relatively tight on the maglite so not expecting it to go anywhere.

Update : I dropped the torch head in the pool carpark, it worked for a while and then stopped after it had completed a successful 4m depth test. It transpired the glass on the reed switch had broken. I replaced it with another one but will have to keep an eye on this, as it may not be robust enough...

Dive Light - Part #4 - Canister WIP

Its a sort of canister, rather more of a test tube, but it is water tight to 35m (114ft) when i wrote this, can contain 3 ultrafire batteries and is easy to create.

The end plugs are from ebay, and compress sufficiently to give a good seal. One of the plugs came with a hole already in it, its quite a small diameter hole so needs to be widened with a drill bit. Just enough to force the cable through. I put some gasket sealant on the cable and pulled it through which glued it tight.

I think this enclosure has quite a good future for projects......

and "fitted out with some batteries.... Two 18650 cells, 4.2v each max giving 8.4v in series... 

To be attached around my STA on a wing. Tubing is surgical type, made of rubber and stretches round the STA under tension.

Run time was approximately 1hr with these two batteries.

Springs came from original maglite and another one I had hanging around.

Block connectors are trimmed down to fit in the tube.

The battery circuit, which is two cells in series, is created by  a thin wire running from one end to the other. Because the batteries are such a tight fit in the arcylic tube, I couldn't find a cable that would fit in there with the battery, so the only answer was to remove the cable sheath (still tight but works).

Cable is hard core cable from a 15a mains cable.

This is a picture on a Frog Indigo wing... 

With the cylinder on the STA it should keep the tube in place.

Dive Light - Part #3 - Light Head

The light head is a standard 3D maglite I found on ebay, it had a rotten battery in it that was stuck but this didn't matter for my use. 

The body of the torch is quite soft metal so a junior hacksaw was enough to cut it, cut just after the switch assembly so as to preserve the end of the torch.

To Disassemble the torch have a look on the web for instruction or at the link below.

The Head of the lamp is screwed to the body of the torch, the cut end now fits into the torch grooves.

I found it didn't go in a long way, so ground the threads down with a small grinding wheel. It didn't make it go in a great deal more but enough to jam it solidly and glue with the liquid metal (JB Weld). This was liberally spread onto the two mating surfaces, the cut end of the torch body and the inside threads of the torch head. 

The picture below shows the resulting join between the head and the shortened barrel.

Here is a view from inside the torch head, the liquid metal sort seeped in quite a bit to cover the join and cover the ground down thread of the inside of the torch head.

The end cap was drilled out to accept the cable gland. The material used on this end cap was not so soft and I had to ask a friend to drill it out as my meagre drill slipped all over it... Recommend you have a proper bench drill for this.
The end cap screws off, I had purchased a new o-ring to replace the one that was there originally,however, in the end I decided to use instant gasket material, apply wet and screw up, no o ring.

The logic being, I can unscrew it and start again easily < update near impossible to get off !>

Apply silicon grease to the cable and o-ring within the cable gland.

The o-rings in the head unit are all upgraded ( see parts list), there are three, one around the head as shown below....

A second o-ring in the lid or rim of the head.....

The third sits on the lense itself in the groove , this is the underside of the lense or the edge that faces in.
The original lense from the maglite was a flimsy piece of plastic so I replaced it with two pieces of acrylic glued together, one with a slightly smaller diameter so that the o-ring is kept aligned to the torch head.

Here is a side view with the o-ring mating to the torch head and the lense.

When its all tightened up, the first o-ring should just be visible.

All o-rings are greased up with silicon grease.

The light head I choose was driven by the desire to have as many lumens are possible, in the end it probably wasn't the right choice as it took an awful lot of grinding to make it fit and i was lucky it still worked afterwards!
I've no metal working tools are such, only an angle grinder I used for cutting some concrete posts! But it can be done, put the light in a vice and gentle grind away. Stopping frequently so as not to let it get too hot.
Keep comparing the size of the drop-in with the opening in the torch, it will need a lot of grinding to get rid of all the fins...

Here is what it looked like before I ground it up!

5*Cree R2 1200-Lumen White Light Drop-in LED Module (52.7mm*42mm/8.4V Max)

Nice snug fit... the edging on the drop in needs to be completely removed so that the lense sits directly inside the torch head in order to make a good seal.

The end product.

Dive Light - Part #2 - Parts list & Sources

Parts list & Sources

Old 3D maglite torch

Get an old one off ebay, it doesn't matter what condition its in...

Cable - Retrieved from an old kettle plug. Its was chosen to fit the cable glands. I bought those first and then found a cable to match.

LED Drop-in

5*Cree R2 1200-Lumen White Light Drop-in LED Module (52.7mm*42mm/8.4V Max)

5*Cree R2 1200-Lumen White Light Drop-in LED Module (52.7mm*42mm/8.4V Max)

Acrylic Tube

From ebay, these fits the batteries I already had, three Ultrafire 18650.


Rubber stops

From ebay to fit the above tube, 19mm 1-Hole Red Rubber Stopper Bung Laboratory, you need one with a hole for the cable and second one without a hole.

Cable gland

M20 CABLE GLAND, HYLEC, 56020M-LLNC, again from ebay for a couple of £ each.

0 rings

I bought two sizes, one for the head unit and one for the base of the light unit, in the end I didn't bother with the smaller one on the base, but here are the sizes:

Nitrile Rubber O-Rings 48mm x 2mm 48 ID x 2 Thick NBR70

BS124 Nitrile Rubber O-Rings 31.42mm x 2.62mm 1.237" x 0.103" NBR70

Other bits/off ebay.



Sunday, 11 November 2012

Dive Light - Part #1 - Intro (WIP)

Dive Light - Part #1 - Intro - Maglite conversion

I've a UK Kinetics HID Light Cannon which is a great reliable torch, has great power output and the light colour is a nice white...But its a little old hat compared to the LED lights of today and its just to big for my more streamlined diving profile and hence the desire to build my own led umbilical came about. Now I'm cheap so i've been scouring the internet for parts and ideas, luckily i'm not the only one doing this so there are loads of  good ideas out there... Hopefully I will add some of my own to the mix...