Sealing electronics

[miketsp]

I haven't found any reed switches that take more than 1 amp........sounds like alot, but not enough "head-room" for some apps..... at least I'd like a bit more . What kind of lights are you talking about..........dive lights?

I control anything!
In the case of a heavy amperage, example 50W Halogen bulb at 12V ie over 4A, I just add a cheap circuit using 1 small signal transistor, 1 small electrolytic cap (1uF) a few small resistors and a MOSFET, IRF540 or similar (28A / 100V). This circuit also gives me soft-start (0.5 second ramp up) so no risk of blowing bulb at turn-on. The on resistance of the MOSFET is below 0.06ohm so almost no power loss. At 4A no heat sink needed.
For data sheet see
http://www.ece.utexas.edu/~valvano/EE345M/IRF540.PDF

 

[DepthCharge]

I didn't say it couldn't be done..........I just want to keep the components to the bare minimum. The advantage is limited holes in case..........drawback is added components
The other way....advantage is less components.............drawback is additional water ingress point. Can be a difficult choice.
The one problem that I encountered with the reed switches, is that the case had to be substantially thinner at that location. I'm not sure what the pressure would do at that point, granted it's a small area, but it is a good deal weaker. I'm talking about 140-150 psi +.
I did some testing a while ago with reeds and magnets. The distances wern't that great with most of the ones I used ( I'll have to see if I still have the chart) IIRC all were less than 0.1 in. I haven't tried some of the newer exotic magnets. Problem with the exotics, is that I can't find any that are small enough. I'd have to move the reeds farther apart, making the case larger when I really want to make it smaller.
I'm already cramming 6-7.2 V 1.4ahr batteries in there along with everything else. (CCR controller).
What kind of depths have you had your light to? The depth thing is truely my biggest concern. Maybe I'll make a housing with the reed pocket and see if the pressure pot will break it.

 

[miketsp]

Using ordinary magnets recovered from an aquarium pump, 1.5cm x 0.8cm x 0.5cm I have operated reeds through a pvc wall of 1cm and through 4.5mm of structural grade aluminium alloy (it's the hardest you can buy).
I do the mechanical designs to 50m, max tested 25m. I have attached photos of an early prototype - but this is a pretty big housing. Front is 10mm polycarbonate backed by 4.5mm structural aluminium. Rear faceplate is 4.5mm structural aluminium. Battery 12V 9AH. In this example the magnet slides along the outside and locks into 4 positions, 20W 38degree lamp, 50W 8degree lamp, off, and "charge".
The charging terminals feed the battery through a diode to avoid electrolysis when in use. The rear magnet position operates a reed which closes a relay to short out the diode.
The only opening in the enclosure is 2 tapped holes in the aluminium backplate for long term gas release. In storage the screws are left out.

 

[DepthCharge]

For some reason, I can't open the thumbnails. If you can you can send the pics to dpthcharg@yahoo.com. I'd appreciate it.
WOW! you're getting alot more distance than I was getting, which was why I gave up on that way. I'll have to see what magnets I can find to use. Do you have any problem with the magnets rusting? The aquarium pump ones are coated I'm sure, but I don't have a busted one to take apart ;-). How about placement of the reeds? Specifically, how close can you get them before the magnets cause two to be active?

 

[miketsp]

For some reason, I can't open the thumbnails. If you can you can send the pics to dpthcharg@yahoo.com. I'd appreciate it.
WOW! you're getting alot more distance than I was getting, which was why I gave up on that way. I'll have to see what magnets I can find to use. Do you have any problem with the magnets rusting? The aquarium pump ones are coated I'm sure, but I don't have a busted one to take apart ;-). How about placement of the reeds? Specifically, how close can you get them before the magnets cause two to be active?

OK mail sent, let me know if you don't get it.
As for opening the thumbnails, maybe you have a problem with file association, they are jpeg & not jpg.

I just varnish dipped the magnets and never saw any rust.
There are magnets which are just cheap iron bars magnetised - those will rust quickly. Normally the ones I use look more like ferrite (as are the ones off the aquarium pump).
You could probably try "tool dip". It's like a rubberised dip to put on handles of tools.
Since I am operating the reeds some distance away, they also have to be more spaced. But you could try different orientations, alternately 90degree shifted and then rotate the magnet.
Thinking about it & based on the fact that any iron in the path will concentrate the lines of force, it should be possible to pin part of the path. Imagine you have a wall of PVC (or similar) say 10mm thick with a reed behind it.
Now drill 2 holes 3.5mm diameter, depth 8mm into the wall, separated by the length of the reed. Into to 2 holes you stick 2 soft iron pins 3mm diameter, 9mm long and epoxy them in.
The wall has lost almost nothing of its structural resistance. Put the reed behind the pins and then pass the magnet across the other end. You should get high resolution operation. Probably makes no difference if the pins go outside inwards or inside outwards, although in the latter case there will not be any corrosion problem.
This idea just ocurred to me and is probably worth experimenting.

Mike

 

[DepthCharge]

OK mail sent, let me know if you don't get it.
As for opening the thumbnails, maybe you have a problem with file association, they are jpeg & not jpg.

I didn't get the e-mail....because I gave the wrong address it's dpthchrg@yahoo.com Pretty dumb huh? :doh:

I just varnish dipped the magnets and never saw any rust.
There are magnets which are just cheap iron bars magnetised - those will rust quickly. Normally the ones I use look more like ferrite (as are the ones off the aquarium pump).
You could probably try "tool dip". It's like a rubberised dip to put on handles of tools.
Since I am operating the reeds some distance away, they also have to be more spaced. But you could try different orientations, alternately 90degree shifted and then rotate the magnet.
Thinking about it & based on the fact that any iron in the path will concentrate the lines of force, it should be possible to pin part of the path. Imagine you have a wall of PVC (or similar) say 10mm thick with a reed behind it.
Now drill 2 holes 3.5mm diameter, depth 8mm into the wall, separated by the length of the reed. Into to 2 holes you stick 2 soft iron pins 3mm diameter, 9mm long and epoxy them in.
The wall has lost almost nothing of its structural resistance. Put the reed behind the pins and then pass the magnet across the other end. You should get high resolution operation. Probably makes no difference if the pins go outside inwards or inside outwards, although in the latter case there will not be any corrosion problem.
This idea just ocurred to me and is probably worth experimenting.

Mike

I never would have thought about doing the pin thing..........like the idea. Will give it a shot.if you don't mind :unsure: