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Hey everyone! I've got a LOT of HID lighting in use around the home and shop, and I very much enjoy them (so I have no interest in switching to LED or fluoro), but it is getting quite hard to source the bulbs when it comes time for replacement.
I'm using all Probe start bulbs and ballasts (ANSI M57) which is basically just an inductive reactor to limit current while applying mains voltage between a main electrode and a small low current starter electrode, which ionizes the fill gas enough to ignite the main arc between the two main electrodes. These bulbs typically fail by way of ablation of the starter electrode, resulting in a failure to start. If you take the used up EOL probe start bulb and place it in a Pulse start ballast, which uses a 1.5-5kV pulse to ignite the arc, they will fire right up and work for thousands of hours more.
The problem is; I have perfectly good probe start ballasts, but finding probe start bulbs is not easy. Most places that still use HID have switched over to Pulse start bulbs and ballasts. It isn't financially feasible for me to go out and spend several hundred dollars per fixture to upgrade to Pulse start ballasts. I know there are "core, coil, and cap" type pulse start ballasts which use an external igniter similar to what I need, but these ballasts have a tap on the secondary winding which supplies a differential voltage to the igniter. I don't know the voltage difference, nor do I know if they can be used on a standard probe start ballast which has only one output voltage, nor can I find a schematic of the internals of one of these igniters to determine what goes on inside the magic box, so to speak.
I would like to design a small, preferably mains (120V) powered circuit that I can wire in along with the standard M57 reactor ballast that will apply a suitable ignition pulse to the lamp. This way I can greatly extend the life of the bulbs I currently have, as well as use the cheaper and easier to find Pulse start bulbs when it does come time for a replacement.
I've tested simple common HV sources and found that HF AC is more than capable of easily igniting the arc, but it is hard to find AC flybacks and the support circuitry and transformer make it kind of bulky, not to mention the need for a stepdown transformer for the LV supply. Likewise a SSTC ignites it with ease, but I'm not about to build and mount a small SSTC on to each fixture! I couldn't seem to get ignition from DC flybacks, but I suspect the trouble was rather from the difficulty of coupling the HV to the bulb; it isn't like I could just wire it straight in without causing reflected power (going from sec to pri) from being burnt up in the body diode, and being DC I couldn't just loop some wire around the bulb like I did with AC.
So, this leaves me needing a version of the standard igniter for MH/MV bulbs that does not require a separate tap on the reactor secondary to function. Does anyone have any ideas for a circuit I would need to make to accomplish this? Hell, there may be a simple modification I could do to standard igniters to get it to work, but I have no expertise in this area.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
You can get igniters with built-in pulse transformers that don't require a tapped choke, like the ZRM series from Tridonic. Or if you like living dangerously, you could try a starter from a high-powered fluorescent tube fixture.
If designing your own, the basic circuit is the same as the igniters for gas cookers and boilers: a capacitor charges to about 300V, and discharges through a gas spark gap or SIDAC into a pulse transformer. The pulse transformer secondary goes in series with the lamp.
Finally, you could go round every evening waving a SSTC on a pole, like a Victorian lamplighter. :D
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Yes, there are cheap and small ignitors which superimpose HV pulses on the ballast output. At least here in 220-240 V land they are very common. I have a schematic for a 1 kW ignitor which I designed for my needs, if you want. It takes 230 VAC input but might work for other ballast output voltages too.
Another, less efective but simpler option, is to wire a fluorescent starter in series with a capacitor and a safety resistor, all this in parallel to the lamp. For ballpark values try 1-2.2 uF 1000 V for the cap, and 220 ohm 5 watt resistor. The fluorescent starter must fire reliably at the ballast output voltage but must stay open at the lamp arc voltage. Two starters in series are possible.
You can get igniters with built-in pulse transformers that don't require a tapped choke, like the ZRM series from Tridonic. Or if you like living dangerously, you could try a starter from a high-powered fluorescent tube fixture.
If designing your own, the basic circuit is the same as the igniters for gas cookers and boilers: a capacitor charges to about 300V, and discharges through a gas spark gap or SIDAC into a pulse transformer. The pulse transformer secondary goes in series with the lamp.
Finally, you could go round every evening waving a SSTC on a pole, like a Victorian lamplighter. :D
Eureka! Thank you very much, this is exactly what I was looking for. Apparently, superimposed pulse ignitors with ballast isolation are widely available in the UK. I wonder why they are not used here. I found a single Tridonic ZRM 175W compatible pulse ignitor on US eBay for $12 shipped and grabbed it. The spec sheets all list >198V input required, but a quick measurement of the OC voltage of my ballasts confirmed that they're all basically current limiting step up autotransformers putting out ~230Vac, so I think it should work fine.
If it doesn't work then it isn't a big loss and I can live with that. Then, I'll have to try the DIY approach. I had thought it might be as simple as dumping a cap across a pulse transformer, but wasn't sure, having never seen the insides of a commercial one. Hardest part would probably be sourcing suitable transformers inexpensively. I had considered trying a fluoro starter, but didn't want to muck about with possibly blowing them up and I had no idea if it would work or not. Thanks!
Oh, and the idea of igniting the lamps by hand with a SSTC Victorian style had crossed my mind, haha! Would make one hell of a steampunk set up, a VTTC started MH lamp! Too bad I'm not really into steampunk and haven't ventured much into valves.
Dr. Dark Current wrote ...
Yes, there are cheap and small ignitors which superimpose HV pulses on the ballast output. At least here in 220-240 V land they are very common. I have a schematic for a 1 kW ignitor which I designed for my needs, if you want. It takes 230 VAC input but might work for other ballast output voltages too.
Another, less efective but simpler option, is to wire a fluorescent starter in series with a capacitor and a safety resistor, all this in parallel to the lamp. For ballpark values try 1-2.2 uF 1000 V for the cap, and 220 ohm 5 watt resistor. The fluorescent starter must fire reliably at the ballast output voltage but must stay open at the lamp arc voltage. Two starters in series are possible.
Luckily most 175W Magnetic HID ballasts used here output ~230V OCV due to them being just current limiting autotransformers. I'll definitely request your schematic if the cheap commercial one I got does the trick. I doubt I could reliably find more available here across the pond.
Also, thanks a ton for the fluoro starter option info. I hope I don't have to try it but I certainly will if need be. How much less effective is it, and in what way? Does it blow through starters often or is it just a matter of it failing to ignite? IIRC the voltage across the ignited lamp drops to around 2-5Vac. I'm not even sure if I could find fluoro starters rated for 230V here in 120V land.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
The starter method is less efective in a way that it generates lower voltages. Most sodium lamps fail to ignite on it, with halides there is a better chance, but still some lamps fail to light up. The life of the starters should not be affected. You can connect two 120 volt starters in series.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Starters are non-linear, I don't believe they can be connected in series. One will stay closed and the other will take all the voltage.
Like most other discharge lamps, fluorescent tubes need more than 120V supply voltage for stable operation. They all have an arc voltage of about 100V, so 120V doesn't provide enough headroom. I think in America, fluoro ballasts are also step-up autotransformers, and their starters must also be rated for about 240V.
Registered Member #3343
Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311
Sigtur:
The ignitor for metal halide bulbs are a small tesla ckt... Believe! It is a small tesla coil in series with the conventional basllast, that add 3~5kV pulse to 230v line in order start the bulb, BUT stop imediatelly the bulb glows . The ignitor has to be wired 1-2m close to the lamp. It is cheap device, and you may buy it in a nice lighting store These ignitors uses the SiDAC device, Please see the attached data sheet , if you canot see, send me a PM.
See figure 10 a typical metal halide ignitor
I have used sidacs to make arc starters for arc welders.
Excellent! Just the schematic I was looking for, thanks Newton Brawn!
(for the benefit of readers who may face similar issues, be aware of the following:) The type shown in the schematic, which has one HOT input from an untapped ballast, one Neutral, and one HOT/HV output to the lamp is unfortunately not available domestically in the United States. It is, however, widely available in the UK (and presumably elsewhere) as evident in the searches I did once learning of their existence.
Here in the United States all that is available domestically is an ignitor which can only be used with a tapped ballast as it is unable to carry the ballasted current and is thus wired in parallel with the lamp (unlike the ones in UK which are in series with the ballast current). These ignitors cannot be used on untapped Probe Start ballasts (the ones I have) as the ballasts are not designed to withstand the ignition pulse voltages and can arc over internally causing a fire hazard (and destroying the ballast!). Tapped ballasts are given different ANSI designations and are designed to withstand the high voltages and be used with ignitors. Even if I could find a US available ignitor that would still output the HV start pulses when wired to an untapped ballast (both the input to the starter and the output from the starter would be effectively shorted), since there is no isolation between the HV and the ballast in US Ignitors it would be unacceptable to use. The linked schematic should solve this issue, but of course one has to find a source for suitable HV pulse transformers!
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Just make the pulse transformer yourself, it is very easy. Get a core from ATX transformer, wind around 3 turns of primary winding and 30 turns of secondary winding. The wire gauge depends on the carried current. Keep the coupling as high and possible and use HV-capable insulation (interlayer and other).
Here is the simplest superimposed-type ignitor circuit, using an SCR:
Got the Tridonic ZRM Superimposed ignitor in the mail yesterday and installed it in today. Fired up my protected PowerStrike Pulse Start bulb immediately. Surprisingly it would not start my probe start bulbs, but in retrospect it makes sense that the probe start resistor is likely excessively loading the OCV of the ignition pulse. It just sat in cold cathode glow mode. When one of my probe start bulbs fully fails to start from probe ablation I'll throw it on this fixture and see if it starts then. For now, this is certainly an inexpensive and reliable upgrade from Probe to Pulse start. Thanks!
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Designing a retrofit HV Pulse starter for Metal Halide and Mercury Vapor HID Ballasts
