sourcing plastic blisters

my current project needs some plastic blisters at least I think that's what they're called think small plastic box with an LED and a couple of IR devices poking out the top I want them to be inside the alleged blisters not looking for waterproof, just to keep the dust off

the application is a limit switch for a CNC mill hence wanting to keep the muck and bullets on the outside and electrons on the inside

guide size is about 3/16" to 1/4" or thereabouts

(I know it's not exactly electronics, but it's damn close!)

are you talking about and optical sensor/switch aka slotted interrupter?

http://www.newark.com/vishay-semiconductor/tcst2103/optical-sensor-switch-transmissive/dp/33C1118?in_merch=Popular%20Optocouplers&MER=PPSO_N_P_Optocouplers_None

almost, except I'm building them from individual parts was looking for a sort of dome shaped window they could peer through

seems what I was after is called a LED lens

thanks for taking the trouble

cheers Mike

wish I'd seen those first though I think I paid more for parts than for the whole unit :(

You shouldn't need anything for the LED; just drill a hole large enough for the LED (or if you want to get fancy, there are snap-in LED bezel inserts for different sized LEDs that you can use - makes the drilled hole look more "professional"), put the LED in place (with wires/leads), then blob some hot-glue or silicone into place. An LED is mostly cast plastic around the part that emits the light - no dust or water can get inside it (but it can get around the hole edge - which is why you blob on some silicone or hot glue).

As far as the IR device(s) are concerned - that can be trickier, and I don't have a ready answer (ok - maybe one). You can't just use any old plastic or glass lens/bubble - it must be IR transparent (otherwise whatever it is sensing will be missed or attenuated in some manner). The only option I know of off-hand (short of going to edmund scientic/optics and ordering IR transparent plastic or glass - which is another option, I suppose) would be to use some unexposed processed 35 mm film. Go down to your local dollar store or whatnot, buy the cheapest roll of 35 mm film you can, take it out the box, drop it in the processing cannister, and have it processed (tell the clerk processing it what you are doing - maybe they can "process" it, but not run the photopaper - you don't need a bunch of blank photos - just the processed film). When you get it back, the "negative" strips will be opaque to regular light, but transparent to IR (if they aren't fully opaque, double up the strip). Alternatively, if you have some 35 mm negatives lying around, look thru them and see if any have leader or "blank" opaque areas - sometimes you get that at the beginning/end of the roll.

hmm that's made me think I didn't check if the lenses are IR transparent they should be here in the next day or so, a quick check will reveal all

you're right about the red LED though - a small hole and some glue will probably be fine

I'm not too worried about blocking visible light as the prototype works a treat "out on the desktop"

thanks!

mmcp42: hmm that's made me think I didn't check if the lenses are IR transparent

Easiest way is to use a camera without an IR filter, and view the transmitter through the lens or plastic.

Then again - it wasn't completely clear whether your IR device was an IR LED (probably not, as we wouldn't be having this discussion - an LED is an LED), an IR receiver (little metal can with extra decoding electronics for the carrier signal filtering and such), or an IR-sensative phototransistor. If it's a phototransistor, depending on its construction you might be able to do the whole drill-n-fill routine on it, too!

mmcp42: they should be here in the next day or so, a quick check will reveal all

you're right about the red LED though - a small hole and some glue will probably be fine

If its just for moisture/dust prevention, it will probably be OK; now, if you were putting this device under water or under pressure of some sort, that's a different scenario, of course...

;)

mmcp42: I'm not too worried about blocking visible light as the prototype works a treat "out on the desktop"

thanks!

I wasn't sure if you were or weren't; I just wanted to mention something that was IR transparent and cheap to come by (you might find a piece of ordinary glass or acrylic to be transparent enough, if you need broad-spectrum coverage - all you'd have to do is cut/drill/bore a hole in your case, then mount the "window" using some epoxy or cyanoacrylate glue). Good luck with your project!

:)

cr0sh:

mmcp42: hmm that's made me think I didn't check if the lenses are IR transparent

Easiest way is to use a camera without an IR filter, and view the transmitter through the lens or plastic.

Then again - it wasn't completely clear whether your IR device was an IR LED (probably not, as we wouldn't be having this discussion - an LED is an LED), an IR receiver (little metal can with extra decoding electronics for the carrier signal filtering and such), or an IR-sensative phototransistor. If it's a phototransistor, depending on its construction you might be able to do the whole drill-n-fill routine on it, too!

the red LED is just an LED the IR pair are an IR LED and IR phototransistor - reversed diode that conducts when exposed to IR tried all my cameras - all have IR filters fitted - dammit! but since I have a prototype that works, just popping the parts inside the lenses will quickly determine if they still work

watch this space [ ]

cheers Mike

tried all my cameras - all have IR filters fitted - dammit!

You will see an IR LED through any camera viewfinder. If you are not seeing it it is not lit.

hmm I tried my Canon 5D classic and Mk II also a Canon Ixus

nothing in the viewfinder, or on "film"

device seems to be working fine though

the viewfinders are all optical, so not quite sure how they would show IR the sensors do have IR filters so that's why nothing shows on "film"

...

An optical view finder will not show it but the IR filter used is not good enough to keep out the light from an IR LED. If you are not seeing it on a recording it suggests to me that it is very dim. What voltage and resistor are you running?

5 volts 330 ohms 1.1 volts across the IR LED so current is 3.9/330 = 18 mA

so just shy of 20 mW?

That is very low for an IR LED, what does the data sheet say? I would expect a much lower resistor in the order of 33 to 100R.

you're not wrong 50mA typical, max 100mA continuous, max 1A peak

seems to work ok though but that might explain why the cameras can't see it

cheers Mike