Working on a 75 watt spot, any suggestions?

[Tater Rocket]

I have my 75 watt mr16 bulb right now, $5 at lowes. They also had three packs of 20 and 50 watt bulbs (from westinghouse) for $10, I had one of those at first, hooked up the 20 watt to my car cigarette lighter plug through a cig plug cord I have (like 10 feet long, maybe part of the problem), shined it in my eyes, didn't think it was bright enough. Same for the 50 watt. The 75 still doesn't seem THAT bright (which should be blinding, right? That is why I think I need to get the DMM and see the current draw, but my darn father took it to the apartments in his electrical box, what was he thinking? ;-) )

Anyway, I am currently taking suggestions for the casing I should use for this light. It fits quite nicely in a D cell mag casing, and the business next to our apartments is a glass shop (mom is friends with the owner), so I don't think getting a thermally-safe lens will be a problem (especially since I will need one for anything I choose to use as my case). With a LITTLE bit of sanding on the inside of a 1.5 inch slip-on PVC connecter, the bulb would fit perfectly. Then, I could take some inch and a half PVC, bring it up through the back, then use a reducer to reduce it to whatever size I think is most comfortable in my hand (this wont be too expensive, I beleive i have some inch and half PVC laying around, and the connecter is 39 cents, so maybe a couple dollars). Any other suggestions? The mag case would probably be kind of hard (and expensive, I wouldn't want to make my 4D mag plug in only, I like it being portable) to do because of the pr base holder in there. However, the bulb WILL fit in there with a pr BASE in there, so is there any way to make a connecter out of a PR base so that the mr16 bi-pin base will be able to slip in there? That isn't that important though, because I'd rather use a custom case anyway.

Do you think PVC would be able to handle the heat generated by a 75 watt bulb? Am I going to have to use aluminum or copper (do they even make 2 inch copper pipe? If they do, I'd probably have to buy a full 10 feet when I would only need 3 inches or so)?

I guess my main three problems are connecting the bi-pin base to the power (which shouldn't be too much of a problem, you can solder onto the pins can't you?), finding a suitible casing (though this shouldn't be that hard either, I am thinking a 2 inch long piece of 2 inch ID pipe reduced to 3 inches long 3/4 inch or so OD pipe for the handle and it shouldn't be all that hard to find), and also the power... Does radio shack sell the female (I guess it is, like what is normally plugged INTO, say you have your wall transformer with the cylindrical piece with the hole in middle, the thing THAT plugs into is what I need.)? Surely it would... I think I will be heading over there tonight, shouldn't be more than a dollar fifty or so.

So I guess this wont be too much problem if I can get a good case and be able to solder to the pins. What do you all think, a 5 inch long 75 watt light? Yes, it is going to have limitations having to be plugged in, but the plug I have is 10 or 15 feet long (which may have way too much resistance, which may be why it didn't seem bright enough, I will try later with a salvaged (off of a CB plug we made) cig plug and heavier wire and see if it is brighter). Suggestions... Comments?

Spudgunr

(BTW, yes, basically I could have just emailed Klaus or Phantomas since they have used 50 and 75 watt mr16 bulbs before, but hey, then I can't share with you all that I am gonna be the brightest 17 year old around here.... I can just imagine it now, this one guy at school carries a half million candle power spotlight in his truck to shine at people if they make him mad.. I can get back if I want to :) Yeah, I know that might wont have as much knockdown power because it is most likely a lot wider beamed, but hey, overall it will be brighter... (no, I don't know what the beam angle is for this light, it wasn't listed on the package)

 

[Tater Rocket]

Well, great, maybe it won't be that bright... I just tested the bulb again now that it is darker outside. No wonder this little 75 watt lamp didn't seem bright, it must have a HUGE beam angle! From my car to my neighbors house, it lit up the ENTIRE side of the house. It doesn't have much more than a 100 foot effect range, and at that distance it lit up an entire two story house that was fairly long (the beam seemed slightly oblong, the bulb doesn't look centered, it looks like it is leaning to one side.... will have to check the other 75 watt bulbs at lowes for that). However, what I may do is buy one of the (puny, lol) 20 watt, 8 degree beam lamps from lowes. I was not wanting to do this though not only because it is ONLY 20 watts, but because that bulb alone was $9 while the 3 pack of the others was $10. Higher effeciency possibly? My other choice is General Electic bulbs from Home Depot for $9 each, they have the 20, 35, and 50, but no 75 IIRC. What I want is a beam of 8-15 degrees in a 75 watt bulb, preferably 8 degrees, but I don't think they make such a beast in MR11 or MR16 (not sure of the difference, they looked the same) base with the reflector. Hmm, good idea, doesn't exactly pan out though :( Well, maybe the 8 degree ones will, we'll see I suppose, but I don't want to spend another 10 bucks for just one bulb. It will be good though because I should be able to easily switch bulbs (assuming I can figure out a way to have these bulbs just PLUG into a jack, because then I could have the handle supply power, and the head just plug in to the handle (if PVC, it would just slide on snugly then I would use a screw or three to make sure it would not fall off), that would be nice.

The wide beam, 75 watt bulb will be good though for "Winter Patrol" (a feed-the-homeless thing I just got in to, there are a few dark alleys and the single tunnel that runs under St. Louis that needs to be lit so we can check for people to give food to).

Spudgunr


(edit: Just checked out these two posts and realized I am really long winded...)

 

[Graham]

Are the bulbs you're looking at sealed units, with a lens on them?

I'm in the process of doing a similar thing, although I want a portable light, currently looking at multiple NiMh AA combinations like Klaus and the others, as well as a small lead-acid battery.
I've found some MR16 style lamps here, which have the beam angle marked - narrowest is 17 degrees. They are all sealed and have some kind of glass lens attached to the reflector.

I also found a small one - only 3cm across, which is 35w, but as the lens is curved slightly I suspect it is a wider angle (not marked). Anyway, I'm going to see if I can use it to make the world's smallest 35w halogen flashlight!

Graham

 

[Tater Rocket]

Yeah, I want to do a battery powered version later too, but cannot afford that many batts plus a new light case! One of the few labeled 35 watt bulbs I saw had a curved lense, and it WAS flood (it was the ONLY one with a lense at lowes, home depot had most of them with a lense). However, not having a lense wont be too much of a problem with me, I can most likely get heat-resistant glass (though not sure how to cut it into a circle). I am guessing this bulb is 35 degree, though I don't know. Maybe I will have to try the 8 or 15 degree 20 watt bulbs from lowes or home depot, though I REALLY want a 15 degree 75 watt. I BELIEVE home depot had 50 watts, 15 degrees, but not positive, I am going to run up there and check right now, and I will most likely get back before you post again. How much are bulbs in your area?

Spudgunr

edit: BTW, if I can get the round glass lense, is it okay to epoxy it on to the bulb if the epoxy runs along the outside of the lense? It shouldn't be a problem, and I can always secure the lense with epoxy to the case, then secure the bulb in the case with screws to hold it flush, I'll figure something out, or maybe just buy a lensed version at home depot. Either way, I DO have this unlensed version, and I want to keep it as it is a great area light, so I will have to go ahead and figure out what I want to do with it.)

 

[Graham]

I'm aiming for a narrow angle as well - the narrowest I've seen in a shop here so far is 14 degrees..
However, I'm just about to go out to a different area to look for some myself (as well as cells, casing, etc)

I don't have access to any glass-cutting facilities so I'm pretty much limited to ones which have a lens out of the box.

If you plan to attach the lens using epoxy or something, make sure it is stable at very high temperatures - I think this was also discussed in one of the other topics about making this sort of light. These lamp units get *really* hot..

Prices in my area are pretty high - well over US$10 for these lamps. But then, my area is Japan, so what can I do?

Graham

 

[Tater Rocket]

Well, this 50 watt, 15 degree beam IS smaller and DOES have longer throw (I could light up an entire house at maybe 200 feet, and actually see it, though the beam is more of a yellowish it seems, and obviously not as bright). I may or may not keep it. I need to go get the DMM from the apartments, and the home depot guy told me of an actual lighting store that is basically on the way to our apartments, so I will stop by there. If they have a 10 degree or less beam in 50 watts or 75 watts (or maybe even a 15 in 75, since what I have is I think 25 maybe? just guessing comparing the beam size of the 15 degree and 75 watt), then I will get that and take back the other bulbs. Gotta love those return policies, basically no questions asked.

What should throw farther, an 8 degree, 20 watt lamp, or a 15 degree 50 watt lamp? Anybody care to tell me which will throw farther?

Thanks in advance,

Spudgunr

(BTW, Graham, if I can get the bulbs cheap, I'll keep you in mind and email you. K? Though I am sure shipping to Japan would not make this cost effective unless you bought a few lamps)


edit: hmm, surely this is too good to be true? http://www.bearlighting.com/bulb.php3?part=55105&sid=
That looks like a 50 watt, 4 degree (IF I am reading that right) mr16 bulb with 10,000 hours life! Ok, that sounds a bit fishy to me... It is $11.60 I am gonna check description to see if I can find anything else on it )

(edit edit: well, it was too good to be true http://auroralight.cc/shop/showlamps.asp shows the same thing, but it is 36 degree beam, however, in the first section (not the "ultra spot"), they have a 50 watt, 12 degree lamp for $4 MR16-12-50-EXT No manufacturer listed, but I can always check that in a minute. For 4000 hour life, that is pretty good.)

(edit edit edie: (yeah, this is getting annoying isn't it?) http://www.bulb-source.com/MR16.htm It says free shipping, 5 bulb minimum, but they list all the beam angles and everything, they have a 14 degree 75 watt lite (I want that, I would LOVE an 8 or 10 degree one though). All of the prices are $3.90 each, not bad (really good anyway), with free shipping, sounds like a good deal. Too bad I don't need 5, I only need one....)

 

[Tater Rocket]

Ok, I have a scan of the two bulbs.

The bulb on the right is perfectly centered, the 75 watt bulb on the left is slightly off-centered. Is this normal? I don't think it is, the heat sink stuff in the bottom is all globbed to one side, and the bulb appears to be un-centered by maybe a sixteenth of an inch. Will this cause a very mis-shapen beam compared to normal? I may take it back to lowes and exchange it IF the others are not un-centered also. We'll see tomorrow, it also is on the way to the apartments.

Spudgunr

(edit: Ok, well, the pic isn't showing for me, so the URL to the photo album is: http://community.webshots.com/scripts/editPhotos.fcgi?action=viewall&albumID=31812087 that SHOULD work, we'll see)

 

[Tater Rocket]

Okay, went to a real lighting store today and they can get what I want. I now have on order a 50 watt, 9 degree beam mr16 bulb. It was only $4.14 after tax and 10% discount. On the down side, it will take 3-4 weeks to get here :( So, what I think I'll do is take the $9 one back to home depot (so I have some money, I don't have ANY now, and since I won't be needing it and I will still have the 75 watt one to play with....) and mess around with the 75 watt one. I have some 2 inch and some half inch PVC right now to mount the bulb in and just the half inch as a handle. Do you think the PVC will get too hot if I only use the 75 watt bulb in 5 minute or less bursts? The bulb doesn't have glass over it, so when I mount it for now (before I get that glass, the glass guy closed at 3 today, I was there at 3:30) I will recess it an inch or so, then I really wont have to worry about touching the bulb. Also, I can leave the back open to let air circulate (I will probaby drill a slightly larger than half inch hole in the 2 inch then slide the handle in and glue it or screw it, air can then circulate that way). Do you all think I should find some way to make a copper heat sink? We have half inch copper pipe, and I can get 3/4" pipe, and if the piece is less than 2 inches long I can use the (crap, forgot the name of it, it is on a 16 inch long arm, and the arm moves up and down) saw to saw it length wise then can hammer it flat. I could then spray paint it black and dremel out a rectangular base for the bulb to fit in, then I could thermal grease (don't have any, but that is what radio shack is for) the thing on one side, and see if my epoxy is strong enough for the other side.

Spudgunr

(This is going to be a nice light, wish I had a digital camera)

Currently, I have the thing mounted in a pistol grip toy :) I used an old sega menacer I had been saving for such a project (didn't know it would be THIS powerful though), sawed off the rear handle and bottom part of the handle, then I sawed off the main tube so it was 6 inches long or so. I left two mini-switches in there, so I am thinking about getting a 12 volt relay and using the trigger to actually turn the thing on and off. Then again, I could always just mount a switch on the side. This also have a quite large hole in the back for circulation, and the bulb just happened to fit PERFECTLY (not loose AT ALL, unlike the 2 inch pvc which was about a millimeter or two too large) in the thing. How I wish I had a digicam. This thing looks cool, looks like a little toy gun, but when you plug it in, BAM, you are blinded by the light!

Oh, speaking of light, I took some measurements. When the car was off, there were 12.2 or so volts, when started, there were 14.22 volts. With my 10-20 foot long car plug, the 50 watt lamp was drawing 3.96 amps at 14.2 volts (well, that is what it was not under load, don't know how to do it under load and don't have enough hands) for a total of 56 theoretical watts, but I don't think it was really that high. When I used the shorter plug with a 5 amp fuse (soon to be 10 amps with the wiring replaced so I can use the 75 watt lamp that should draw 6 amps or so) it was pulling 4.16 amps at 14.2 volts for 59 theoretical watts. This seemed MUCH brighter than before, it seemed like 20 or 30% brighter, not like 5% I will be testing the 75 watt lamp soon (oh come on, get dark soon!) with the two cords again as soon as I get done soldering the new, heavier wire onto the clips.

 

[Graham]

Well, I managed to get another lamp yesterday myself. I got a 50w 12 degree MR16, and also figured out a way to test it - since I don't have a car battery or similar high capacity 12v supply, thought I'd have to link up a bunch of batteries. Then I realised - I have the perfect 12v supply - in an old PC lying around. Good, regulated 12v at up to about 9amps. More than enough.

Anyway, tested the smaller 35w MR11 lamp and the new 50w. As suspected, the MR11 one is quite wide angle, so will probably leave it. The 50w MR16 is very nice though - quite a good beam.
I also put together a rechargable battery pack (12 x NiMh AAs), but rather disappointing - after checking back in Klaus' original thread, realised that NiMh cells don't seem to handle high current very well. The recommendation seems to be Nicads, so guess I'll head out today and see if I can get some decent Nicads..

On the plus side, the lamp didn't seem to get too hot at all, so I may not have to worry too much about heat-sinking the lamp after all..

Graham

 

[Klaus]

Graham & Tater,

NiMh - you should try to stay below 1C (just calculate the battery capacity against the watt/12) if you use 12 NiMh cells - so using 1800ma cells no more than 20W - with 35W bulbs you need 2 strings of 12 each - 50W with three strings and so on ....

"More than 5% brighter" - if a bulb gets "overdriven" it not only gets whiter but also gains much more in output percentagewise - also this is an exponential curve (until the bulb dies) - for 10% higher voltage you get 40% more output - for 20% more voltage 90% more output. You can use a nice calculator on the WA site for this. YOur car batery won´t have that 15V under load - this should be pretty much around 12V at that load.

Mr16 bulbs - the reason for using those Philips/Osram "energy saver" or "IRC" or "high efficiency" bulbs was that they put out much more light per Watt - the difference can be as high as 1:2 comparing best to worse - this isn´t as significant when using the car-battery but IMO essential when running on whatever type of small cells.
You might find plenty of info oin those inclusing some links in the old threads.

And no worries guys - even when asking you will certainly still be the brightest guys around - at least the ones with the brightest flashlights

and IMO asking questions shouldn´t be considered a sign of dumbness but rather of smartness.

Oh and BTW - I just guess the PVC won´t withstand the heat - check out something more heatresistant I might suggest - the MR16s get awfully hot - at least put some aluminum foil (like 2 layers) behind the bulb - and using the MR16s with the lens installed you not only get a perfectly working combo with no hassles but also don´t need to worry to waterproof that part as much.

Good luck with your Lightsabers™

Klaus

 

[Tater Rocket]

For a slight heat sink, I am mounting my MR16 to half inch copper pipe. One lead will be soldered to the pipe, the other will have a larger hole drilled and will just run through. I need some heat sink compound that will get hard to act as an electrical insulator. How hot do the leads get on the bulbs? Unfortunatly, the only thing that will be touching the copper pipe right now is the one lead that is soldered on. I was hoping the rectangular part would touch, but I made my hole too large. The 75 watt bulb I have does not have a glass cover, but I have the front of the reflector recessed in the PVC about an inch or more. The only part that touches PVC on the bulb is the reflector. The part that gets hotter (at least in my brief tests) is touching the copper pipe or sits in the center of the 2 inch PVC. Also, the rear is open-ended to allow air circulation. If I notice the PVC becoming unbearably warm, I will then find a new housing for it. I would try it in a 2 C or D-cell maglight housing, but the bulb mounting thing is in the way and I am not exactly sure how to get rid of it. Also, I don't want to spend $15 just for a housing. I just bought my switch and power connecters from Radio Shack, so I will be hooking that up today and hopefully will have it done in the next few hours.

Spudgunr

 

[Klaus]

Tater,

a 35W bulb William measured at 457F after 15 minutes

These are 20Ws numbers: The lens of the bulb got up to 180 degrees F. The back of the
bulb got up to 250 degrees F. The base of the bulb where the square plug
meets the rounded reflector got up to 300 degrees F. Finally, the plug area
of the bulb got up to 275 degrees F.

And its easy to remove the unneeded parts from a Mag - just use a allen key inside the switch - the procedure is explained a couple of times on CPF already - but I understand the cost issue - a Brinkmann 2D is maybe cheaper and the head fits even better btw.

Hope this helps

Klaus

 

[Tater Rocket]

Hey, thanks for those numbers! I now have it finished. You know, it doesn't seem that bright. I guess your eyes get used to looking into really bright lights ;) I currently have one wire of the bulb soldered to that copper heat sink (my handle of PVC is also hooked to that, the copper goes through both sides of the 2 inch, then my half inch is just slipped on). The other pin of the bulb snapped off when I was pulling the wire that was soldered to it! It broke off flush, so what I did was take an exacto knife and scrape away that white cement around the remaining fragment of wire, then I stuck the wire I wanted to solder to it inside, then filled it up with solder. That was SO much easier than soldering a wire to the pin anyway!

As for heat, hopefully that copper will disperse some. The heat will be able to flow upwards out of the copper pipe from the bulb area and from the bottom of the handle. Also, it has a 2 inch hole in back. What I most likely will do is just not leave it on for long. I will have to search later for the mag dis-assembly details. Maybe I should head to some garage sales and just pick up a mag for a dollar or so? If I see a 2 D or C mag for under $5 or so used, I'll get it, and if I find a 5D for under $10 or so, I'll probably get it so I can always make the 24 AA rechargable 20 watt or so light. That would be cool. Currently, mine weights about 4 or 5 ounces (what is that, 120-150 or so grams?) without the power cord (yeah, I made the power cord able to be snapped off, not necessary, but will make storage a bit easier.

My overall dimensions are: 2 inch ID head that is 3 inches long, out of the top of that sticks about a half inch of half inch copper pipe, and out of the bottom is 3 or 4 inches of half inch PVC for the handle. It is quite small and light weight, and I am hoping since it is so small and open it will cool better. I hope it doesn't get hot enough to melt the insulation off of my wires. I'll let you all know later tonight (probably around 10:30 central, when I get home, about to leave for Winter Patrol) how the thing performed in open areas (hopefully in that tunnel under ST.L) and in the city with other lights around.

Spudgunr

 

[Graham]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Klaus:
Graham & Tater,

NiMh - you should try to stay below 1C (just calculate the battery capacity against the watt/12) if you use 12 NiMh cells - so using 1800ma cells no more than 20W - with 35W bulbs you need 2 strings of 12 each - 50W with three strings and so on ....

<HR></BLOCKQUOTE>

Klaus,

Thanks for all that info. I've read through the topics about the lights you've designed, very helpful. A couple of questions though - what do you mean by '1C' above (no doubt its very obvious and I'll bang my head on the desk as soon as I see it..)

Also, have you looked at using larger cell sizes than AA at all? I understand that your intent was to create a smallish light about a Mag 3D size or so, was that the main reason for AA? I ask because just yesterday I suddenly realised I had a good high capacity rechargable battery pack under my nose - the 7.2v Nicad pack which is almost standard for radio control racing cars.

These packs are basically 6 C cells, attached together and wired up with a plug in a very convenient package. They come in various ratings, up to 2400mAh, or 3000mAh in NiMh.
I figured that if I wire 2 of these in series, it will give more than enough capacity for a 50w lamp. The best thing is that these packs are actually designed for high current applications with discharge times of about 30min-1hour.
The cells in the more expensive packs are actually tested and 'matched' for discharge rates to get optimum performance from the pack.
Anyway, I can get 1700mAh packs for about US$15 each if I buy 3, which I intend to do. 2 of these taped side by side is thicker than a Maglite, but still a reasonable hand-carry size. I just need to find a casing..

Graham

 

[Graham]

Klaus,

I think I just figured out the answer myself (the 1C thing). You mean that its best not to exceed the Amp-hour rating for each cell, based on a 1 hour discharge. Is this correct?

For example, 20watts/12 = 1.6W/cell
Each cell is 1800mAh, or 1.8A for 1 hour. P=VI, therefore in the case above 1.6w/1.2 = current required per cell pair. In this case, 1.3A. Or 1.6A, if you assume cell voltage drops to about 1V under load..

Is this your reasoning, Klaus?

Graham

 

[Jonathan]

Spot on. A 'C' rate discharge is a current which would discharge the battery in 1 hour.

Different battery chemistries do better for total energy or total power, and for a given chemistry, battery designs can be optimized for energy or for power.

Energy is to total number of watt seconds delivered over the life of the battery, power is the total number of watt seconds delivered in one second. Some lithium cells can deliver a tremendous number of watt hours in a very small space, but they are limited to a discharge of a couple of mA, and would not be able to deliver much power. They can deliver a couple of mA for years, but could not deliver an amp even if short circuited.

NiCd batteries tend to have lower total energy storage than NiMH, but higher power capabilities. For most NiMH, you really don't want to exceed the 'C' rate, whereas many NiCd batteries are fine at a 5C rate. But there are exceptions!

Racing car and power tool optimized batteries are specifically intended to be used at high rate discharge. Specifically, the 'sub-C' cells are often rated at very high currents. For most lighting loads, the current used will be lots less than these cells can handle. For example, here are some cells tested at 20A (something like a 6C discharge), and these specific NiMH and NiCd cells did just fine:Magellan Tech. Sub-C cell tests (Note, however, how the NiMH cells were at the top of the chart for the 20A test, and at the bottom on the 35A test.) A 12 cell NiMH racing pack would be darn near ideal for running 12V lamps up to 150W or more, if you only needed a short run time (say 10 minutes).

A 12 cell NiMH racing pack would be darn near ideal for running 12V lamps up to 150W or more, if you only needed a short run time (say 10 minutes). Using a 14 cell pack with PWM voltage regulation (so you don't burn the bulb on turn-on) and a 35W IRC lamp run at 20% overvoltage (true wattage of 46 watts) would give you about a 1 hour run time of a _very_ bright light.

Regards,
Jonathan Edelson

 

[Graham]

Jonathan, thanks for that very informative reply. Good to know that I'm on the right track.

Sounds like it may be worth paying a bit extra and getting the higher-end racing packs, rated at 2400mAh. I'm particularly happy with this idea as it
1. Appears cheaper than looking for/purchasing after individual cells
2. The cells are already connected together in a low-resistance package, which will be far better than I can do with a soldering iron
3. Have a good connector setup, making it easy to create a system so that I can plug in or remove each pack simply.
4. Commonly available, cheap rechargers, again better than anything I can build.

Because this sort of RC racing is a very popular hobby here in Japan, these battery packs can be purchased quite cheaply, along with the accessories (connectors, rechargers) to use them.

Currently I'm only(!) trying for a 50watt light..but the way this looks, I may be able to build a system which will allow me to swap between a variety of lamps - high power or *really* high power, spot or flood.
It will be thicker than a Mag D size light, but still quite easily hand-carryable.

Also, while out shopping yesterday I noticed that there are also various MR16-style lamps which have a screw in base rather than the bi-pin. The mounting for the ones I saw were called either EZ-11 or E10. Next time I'm out I may get one along with the mounting, and see what its like. It may be a bit more secure/robust than the bi-pin mount. It may also dissipate heat better, since there appeared to be much more surface area in contact with the mounting..

Graham

 

[Tater Rocket]

Ok, didn't get to go to the city tonight, but that didn't stop me from testing. As expected, the light is VERY bright. However, because of the rather large beam angle, the maximum distance is probably around 200 feet. I tested it out on my neighbors house (lol, he is a cop, wonder if he saw the light), it lit up the ENTIRE house (two stories, plus basement) the driveway along the side, and some of the yard. It wasn't BRIGHT at this range, but it was easily bright enough to distinguish everything.

I WISH I could get the Osram bulbs. No place around here has had them, and I doubt they can get them (at least the 3 stores (two home centers and a lighting store) I have visited any way). It would be very nice indeed to have a 50 watt Decostar lamp.

Is there any EASY and more importantly, CHEAP way to get 14 volts into my lamp? I seriously doubt a step-up converter that could handle 6 or 7 amps would be cheap though. Oh well, guess I will have to "settle" for for "only" 75 watts of light.

Oh, for heat: I have only had it on for 3-5 minutes at a time, and during this time, it got a bit warm, but not actually HOT. I don't think I will be having it on for any significant length of time, so I don't think I am gonna have to worry about heat too much. Well, maybe I will if I put something over the back (it is fairly bright backwards too, and makes it kind of hard to see what you are lighting up unless you cover the back end, which I may do) then I will have to worry about heat, but I can probably just keep covering it with my had like I have been doing.

Spud

 

[Graham]

Sounds like you've got a pretty decent flood light there.

I'm not able to get Osram lamps either - I can get a pretty wide range, but all various Japanese brands..

Regarding heat, I noticed the same - I initially tested my 50w lamp with the 12v supply out of an old PC, and it didn't get very got at all for the 5 minutes or so I tested it. I'll have to see what happens for extended use. However, I also don't think I would be using the light for much mor than 10-15 minutes at a time. It may be interesting to make a larger, long-burning version which can deal with the heat though.

Graham

 

[Klaus]

Graham,

exactly - C is typically used to name the Capacity which is measured in A or ma (1000ma = 1A) - so a cell with 1800ma is able to supply 1.8A for 1 hour (ok not really

but at least in theory).

If you look at your bulb at 50W it means it takes 50W per hour at 12V - 50W/12V=~4A - so for 1 hour runtime you need a pack supplying 4A at 12V. As the voltage drop under loads around 1C (like a 20W bulb [20/12=1.66] at 1.66A / hour is pretty much around the capacity of those NiMh AAs) is to around 1.1V I´m using 12 cells which gives a slightly overdriven 12V (like 13 to 14) which helps the efficiency and bulb-lifetime is still OK as the original designed spec is 5K hours.

Those cells in the RC pack typically are sub-C cells - especially designed for high-current discharges. Actually they might have been a better choice than those AAs. I more or less choose the AAs based on own experience with AA but none at all with sub-c´s. Also the sub-c´s wouldn´t have fitted as nice on that Mag-body. We are currently working on that 1 hour / 35W / 24 NiMhs design and William is doing his own body - so we talked about those Sub-c cells and could have used them doing our own body anyway but stayed with AAs due to available experience and the testing already done.

I found a nice website testing and rating a lot of sub-c cells which might be useful for you:Sub-C cell tests - grin - I just see Jonathan beat my on this posting the same site. And he also explained my point on those sub-c´s very nicely and more accurate.

Tater - the mag switch dissassembly is nicely and very much detailed explained at Mag Switch dissassembly - while you don´t need to follow that as closely IMO - but you will get the general idea.

Bulbs - Tater - there is one Sylvania (like the US-partnet of OSRAM) named the True-AIM but only in 37W - look for that "IR" thing.

TRU-AIM IR® MR16
UV stop capsule with axial filament in constant color, hard dichroic reflector and infrared reflective coating on the capsule

Base Wattage NAED Description Voltage Life (hrs.) CBCP Beam Spread
GU5.3 37 58641 37MR16/IR/NSP/10 12 4000 11500 10°
58634 37MR16/IR/FL/25 12 4000 3500 25°
58633 37MR16/IR/FL/40 12 4000 2050 40°

Graham - no idea about which MR16´s are available in Japan - but look for so-called "high-efficiency" or "energy-saving" designs - I could imagine you have those too - just check out the candle power / lumen rating at a given beam angle (like 10°) and choose the best one (highest number) - and I think choosing sub-c cell RC packs is a very smart choice for this app - and using more cells and a PWM like Jonathan suggested is certainly a plus - this is under consideration for the next version of ours.

Jonathan - on a sidenote - how did you and William (and/or I

) ended up in the discussion on that project light ?

Tater - keep the engine running to get more than 12V

Sidenote: There are MR16s specified "Hot-beam" and "Cold-beam" where the cold-beam ones are the standard traditional ones - the bulbs originally designed for application lightning and therefor the designers tried to get less heat into the beam to not generate problems on the target surfaces - so the bulbs back get really hot which isn´t too good for any of our applications - the newer special breed of "hot-beam" bulbs changed that through like titanium / aluminium coating of the reflector and generates much less heat on the back of the bulb but gets warmer in the front and the beam. Unfortunately for me those IRC bulbs aren´t available (yet?) in that hot-beam flavour but I decided to go with the better efficiency / more output and work around the heat issue somehow.

Have fun guys

Klaus