Metal-halide driver current\voltage measurment - Page 1
Forum section: electronics / projects

author: kokodin
author_rank: Regular Contributor
timestamp: July 06, 2017, 07:15:54 am
content: Hello/I am upgrading my ohp/lcd projector for this summer outdoor cinema, and i decided to swap 150w metal-halide lamp to a 250w Metal halide lamp. You know 12000lumen<20000lumen, more lumen more better projector. :]But while buying those stuff i did not check the current values of the lamp, and magnetic balast i bought on a internet sale. Watt ratting matched, suply voltage matched, and a type of a lamp matched so i bought it.After initial hype "it works" i noticed that it is not all that much brighter (and i don't belive i messed up the optics part) , so i begin to look for a cause.Unfortunately seller did not provide electrical parameters of the lamp, it is probably over the counter distribution anyway, because lamp was produced for japanese market. Slovakia made Toshiba lamp, sold to Poland without a word in understandable language. :] model number MQD-TS 250W/WDL/UVS (fc2 socket) and i can't find anything for it. I belive it is a similar lamp in specs to ostam hqd-ts lamps so i assume it suposed to work at 2,8~3AThe problem is my balast lists the current of only 2,13A so almost 1/3 less. At the power rating of 250wthat would either sugest overvolting the lamp to get 250W out of the balast, or undercurrenting the bulb.It light up on the first strike though.So i will have to make measurments to check if by any chance the label wasn't missprinted.Current will be easy, AC clamp on the power cord or bulb lead.But i never measured voltage over an arc lamp, and i am kind of afraid to blowing up my meter. I know it should measure ac lines just fine, but when i think of the strike voltage of a starter (around 6,5kV i belive) John Smith videos come to mind. I know i should measure it when the lamp is lit, but still.I will appreciate any pointers.

author: Kjelt
author_rank: Super Contributor
timestamp: July 06, 2017, 07:57:14 am
content: You'll need a HV (high voltage) differential probe for your oscilloscope. The Voltage across MH lamps are square wave + to - V with a H bridge so you can't measure it properly with a multimeter.Indeed do not connect while igniting, create easy accesible measurement point but take care of the isolation gap for the high voltage.Anyway, the right way is you buy a lamp with the proper companion ballast together, if not all things might go wrong like the lamp dying after 40 hours, OVP and OCP not working properly shutting down the lamp even while nothing is wrong. If you have an intelligent driver with a microcontroller in it and the lamp stays lit for over half an hour you have a decent combination.QuoteDid you measure it before and after with a white screen and lux meter (can be bought for $10) ?If not, you might experience human flaw, when the light is brighter the iris of the eyes close so a human is incapable of estimating amount of light correctly even a factor 2 (unless it is A/B side by side).

author: kokodin
author_rank: Regular Contributor
timestamp: July 06, 2017, 08:24:41 am
content: So it is as i thought, no way of measuring it in my workshop. I don't have high voltage probes and only old crapy analog scope.The lamp stays lit for more than 30 minutes but it is driven by old magnetic balast, so no protection of any kind there, other than a fuse on a power cord. It is not a valid test.As for light sensor, i don't have one. My experience was based on a blackscreen brightness in a dark room.i expected it to be more visable given the same distance and screen size, but it was less visable. Basically contrast between the non-lit wall and black screen is less noticeable, or i am imagining things.edit********************************************i belive i might just bought mercury vapor balast instead of metal-halide one, because amp rattings would match that.

author: Kjelt
author_rank: Super Contributor
timestamp: July 06, 2017, 08:49:48 am
content: Then the only thing left to do is measure the entire device power usage with a standard powermeter (20 euros wallwart thingy).The voltage of the ignited and runup bulb is constant by the way depending on the age of the bulb, the older it gets the higher the voltage. The current through the lamp is the variable.

author: kokodin
author_rank: Regular Contributor
timestamp: July 06, 2017, 09:37:48 am
content: or google translate to the rescueI found the same lamp on a japanese ebay, my only hint right now.Seller listed lamp parameters as:voltage 100Vcurrent 3Acolor temperature 3000K Ra 80 (well i expected 4000k from metal-halide lamp but oh well)light stream 20000lmminimum life expectancy 6000Hacorging to this sitehttp://layrton.com/en/products/hid-built-in-ballasts.htmllabel on my balast is incorect because it states metal-halide nas sodium lamps at the exact specs of that mercury vapor/ metal halide 2,13A balastI might just replace it for the peace of mind to a 3A one, and end on that.

author: Kjelt
author_rank: Super Contributor
timestamp: July 06, 2017, 11:13:38 am
content: 3A 100V than it is a 300W bulb.3000K CT that is for livingroom/ building / garden lighting definitely not for projection systems.Projectors need lamps in 6000K range, no wonder the picture was not very bright.This is useless for projection and the colours of the picture will also all be too redish.

author: kokodin
author_rank: Regular Contributor
timestamp: July 07, 2017, 01:05:25 pm
content: Thanks for info, next time i will be more carefull buying stuff, i localised a store where i can buy osram lamps rated for the new balast i ordered (3A) and they are either 4200 or 5500k so i could chose whitchever i would like.Osram also specyfies them as 98V 3A lamps with "rated power" of 250W so that Toshiba lamp might just have the same power rating that is not consistent with math.I also read something about overdriving and underdriving metal halide lamps, what would heatup and what would blow up if misused :].My Toshiba lamp as it is now, produce fairly blue-ish light, so no much yellows are shown corectly, also not sure how much different the brightness is to the old 4500k 150w lamp. I borrowed old broken dlp projector i might compare brightnes to this, dlp is dead in it but the bulb still works.I forget to add, that my local seller does not know anything about the Toshiba lamp, and specyfied color as white. Translated sites specyfies this bulb color for a range from 3000 to 4200 and one even shown 5000k as an option to chose. so lottery.

author: Kjelt
author_rank: Super Contributor
timestamp: July 08, 2017, 06:36:38 pm
content: Brand new uhp projection lamps are always a bit more blue-ish, this changes rapidly in the first 100 hours and then stays reasonably stable. That is why projectors are best calibrated after that period.

author: kokodin
author_rank: Regular Contributor
timestamp: July 09, 2017, 10:52:42 am
content: Well i played around optics for a little bit and i get a little bit more brightness out of my old 150W setup (around 1/4 more).And i found internet sources to be a little bit inconsistent wth the spherical mirror setup. Should the bulb be located just below reflector radius, or just over the focal point (so the edge of the high presure container be at the focal point or at the center of the reflector radius)I was aiming for 45-60 degree light source with a reflector doubling that and corective lense, but now i just don't know, i was trying to draw this and i just got dumb.So where should the bulb be located exactly? At the focal point as some of toutorials show or at the center of the reflector radius (2x focal point distance)? I don't want for the reflected light to be reflected back at the high presure light source at the 90 degree, because the container itself would be in the way for that light, i don't want it to be at the center of a focal point either , because then all reflected light would only brighten a reflector shaped part of the lcd, most likely circle with a lamp shaped shadow in the middle.Darn those matal halide bulbs, the light source is so big they only make trubbles. :] And i have n idea where to get elipsoidal reflector of apropriate size. Is making lce projectors from ohp pointless?

author: Kjelt
author_rank: Super Contributor
timestamp: July 09, 2017, 02:54:18 pm
content: Sorry I have no optical knowledge, most projectorlamps have the bulb cemented with their mirror.Can you post a picture of your bulb? Does it have an arc of a few mm or do you have a bulb for instance for streetlighting with a long ceramic burner?

author: kokodin
author_rank: Regular Contributor
timestamp: July 09, 2017, 06:57:57 pm
content: 150w metal halide is a Philips MASTERColour CDM-TD 150W/942 RX7http://www.ledvista.ie/images/MASTERColour%20CDM-TD%20150W%20942%20RX7s.jpgi bough two of those last year because they were the cheepest metal halide i could find on local ebay-like site for a specyfic footprint. I wanted thin bulb with small light source in the middle, possibly short and with uv block. It also had to be with the high pressure container in the center of the bulb. I also bought first used magnetic balast i could find, so entire setup with the starter and capicitor was probably under 20$, ohp was free, and reflector was bought at a local home improvement in a form of soup spoon. (90mm diameter and 48mm radius, 30 mm high) since i positioned the bulb across the mirror in the vertical shorter plane, mostly the whole screen is evenly lit. , comparing to 230W bulb of dlp projector (benq mp670), it is around 9 times dimer thoughAs i understand metal halide burners do not like to work standing up, so i decided against using other style of lamp inside/in center of the reflector. Anyway optics of the ohp projector would not allow for standing bulb, not enough space for long bulbs anyway.that is why going up with power i chose fc2 style lamphttp://images.okazje.info.pl/p/dom-i-ogrod/6188/osram-hqi-ts-250w-ndl-fc2.jpgif the color really be too redish i think i will go for that osram 5000k, because it would swap right in with no modufications (after i replace that balast and lamp sockets for the fc2 lamp i have of course)I tryed to focus light reflected from the mirror at the closest to the screen edge of the high pressure light souce bulb thing inside the lamp (and slightly focusing 90mm diameter glass lense on top of the bulb), because it gives the most light on the screen in my opinion, and less light is wasted.If my calculation are correct , fully lit 250w lamp should match 1/4 of that dlp projector brightness, regardless of the light color. That is still only about half of the light produced by the lamp though.

author: Kjelt
author_rank: Super Contributor
timestamp: July 10, 2017, 09:56:24 am
content: I was afraid of this, those are not projector bulbs but regular bulbs for shopping stores and other commercial applications.How were you thinking of using these in a digital projector ? Or did I miss it and are you updating an older 16mm movie projector ?See picture below those are bulbs made for projectors, the arc is extremely small <0,5mm or something like that, while with your bulb has the entire ceramic burner of a few cms act as a light source, that requires totally different optics to converge the light to the small area.

author: kokodin
author_rank: Regular Contributor
timestamp: July 10, 2017, 11:29:10 am
content: Yes that is correct, that is also why i am using normalised magnetic balast. it is more of a build for fun than any other purpouse.i converted something like thishttp://www.aoxing.net/products/s/2010102790534.jpgacording to online manuals and forums.The craze for making those begins somewhere in the early 2000's and i was around 13-15 at the time so i always wanted to make one, and now i did, only i did not think that i will have so much to think about while making it. :] Anyway 3A balast seems to work fine, , picture with the bulb out of aligment with the reflector and no lense is still around the leverl of that 150W lamp at full brightness with the lense, so i might have a little more light if i work the bugs out. and it seems that you were right with the color temperature, with the proper balast picture is more redish/yellowish. Not less bright but it have a different tint to it, with the "blue preset" on the lcd picture seems almost ok though.on the picture is the comparsion to 2300 lumen projector with spotty dlp, i don't think it looks that bad if not for the light coloredit..........................................................................ok a mannaged to get about 1/4~3/10 of the comercial projector brightness out of than bulb/mirror/lense setup, quite a bit more than from that 150w lamp. but then the lense broke :] Didn't like the heat it seems. Without lense it still is a brighter picture than 150w+lense a little bit dimmer than it was with tle lense, but not much , most of the work was done by the mirror. i can always try to lift the lamp assembly up a little bit, that would also help with the brightness, until edes of the screen start to get blury.Well the initial problem with the wrong balast was resolved though and id i would have to change the bulb i know i have to go for 5000k one.

author: kokodin
author_rank: Regular Contributor
timestamp: July 13, 2017, 08:04:39 am
content: There is another question that builds up in my mind.Can you connect 150W metal halide lamp i posted before to an 200/150W AC mercury vapor ballast from a lcd projector?I have like 3 of those from the days i was trying to fix one, and they all works kind of, with no lamp is hard to say, they are Sanyo. So i was thinking about connecting that lamp for a while as a dummy load, just to check if the rest of the projector works. Just stuff that lamp under the bed and test the lcds, polarisers and stuff before i decide to buy a proper, or even chinese replacement lamp.And saying they are Sanyo i ment, they have serial communication between the logic board and the balast, so fulling opto couplers doesn't do much.Philips lamp have those parametersarc voltage 96-110Vcurrent 2,5A start, 1,8A nominal (again that might be a total for a magnetic ballast?, because it kind of make it 200W instead of 150W)strike voltage is around 5kVI don't care for this lamp anymore, kind of don't have use for it, and i have 2 of those. Again only a temporary solution to test the projector logic without auto-shootdown afret 3 failed lamp ignitions. And lamp doesn't have to be in the projector. I seen it done on youtube with 70W metal halide lamp, but i don't know if the current shunts on the ballast were modyfied for that power.

author: Kjelt
author_rank: Super Contributor
timestamp: July 13, 2017, 02:06:46 pm
content: I can't answer that question because it depends how the ballast is programmed.In a previous job I wrote firmware for MH lamps and the software was programmed that the ballast would shutdown at the EOL of the bulb.The EOL was usually determined with the voltage of the bulb but also the number of false ignitions would cause an EOL.So before the parameters were programmed first in many many experiments the bulbs were tested and measured for current and voltage over time and esp. the EOL parameters.So let's say that the bulb had an average voltage of 94-98V when it is brand new and an average voltage of 118-122V when it is 6000 hours (EOL) than the software would kill the power if the voltage after runup would still be below 90V or above 125V something like that.So if your Sanyo ballast does the same for its expected Sanyo bulb and the parameters differ widely from your bulb than it would kill after a few minutes. If not and runs for half an hour than you might have a match with this remark that the Power in the bulb should match the bulb also, if the driver inputs more power to the bulb than in a good case it just wears out sooner, in a bad case it might explode the burner.

author: kokodin
author_rank: Regular Contributor
timestamp: July 13, 2017, 04:38:32 pm
content: So basically i understand that as:"try it out, if it works, it will work, if not, balast will kill the power and nothing else"Well it is a highly sufisticated ballast on the other end of a spectrum than magnetic one. it probably won't explode the bulb or itself :]I have 3 of those projectors for some reason (different model, the same ballast and part of internals) I probably just hook up the one i don't care about and see what happen then. with 5 w led gu10 as a light source of a a5 paper size screeni only need about 5 minutes to test every projector, so even if it kills the power after that time it is ok for me.thanks anywayedit i googled tha balast itself, i have one of those projectors in little pieces about now anywayinput 350V dcoutput 75-110V ACpower output 100-200Wcurrent output 1-3 Ait kind of hook into the range of that metal halide at full power :]edit2well i must say i am surprised, not with the mh lamp iginiting and not blowing up, but with the fact that those projector for 10$ each just might be fully operational with a little bit of love and a replacement bulb, and since they have the same optics i could even stack them :] (for total 5000 lumen projection)edit3i know why one projector did not ignite the lamp. it is because it uses shp dc lamp and ballast is different than in two other projectors, even though all 3 projectors shate the same lower case and most of the internal components.Is there any cheap shp alternative to test that ballast before going internet shopping for that lamp?

author: kokodin
author_rank: Regular Contributor
timestamp: July 16, 2017, 08:10:54 pm
content: One more try for my homemade projector, we'll see what happens.Few minutes ago i find discounted projection metal halide lamp PHILIPS MasterColour CDM-SA/R 150W (4200k)https://images.philips.com/is/image/PhilipsConsumer/25d49f7cad78471dafbca4ad014ec9f9-RTP-global-001?$jpglarge$&wid=1250 for around 18-20$ so i bought it just for fun. Because electrical parameters are close to my smallest ballast for that 150W straight lamp, and since this one comes with a reflector and can stand on its own ceramic socket. Might work better than that 250W lamp with little to none modyfications to the whole thing.I checked the specs of the lamp, it would sadly not fit into any of my sanyo projectors, it is quite big for that.Well i am spending my vacation money on wierd things this year :]