The Lamp Room

I got a gear tray from a 2x58W T8 lantern to repair (well, i already returned it, but i can still ask to get another look at it if we find a solution)

The lantern had a cheepee HF ballast that failed. This was what needed repairing. I put in a VS HF ballast in its place and it works with the new ballast

The lantern also have an EM module - Charger/inverter module with relay, that switches one of the lamps between the normal ballast (for normal operation) or it's own output (in emergency). And this module causes a problem with the lamp detection by the ballast :

If the light switch is on when power returns (that means, 230V is applied at the same time to the HF ballast and EM module), the EM module clicks the relay to connect the lamp to the ballast, but at this point the ballast allready detected that there is no lamp and shut down, so it does not light up (both lamps stay off). Cycling the light switch for a second (that is, switching the HF ballast off, and back on while the lamps are already connected to it) will get the lamps to start normally



The wiring scheme on the HF ballast :




The wiring scheme on the EM module :


It can be figured out, and i confirmed by opening the module and following the PCB traces, that this is what's inside :




The original luminaire wiring :


(the pinout of the original ballast was different, but i drew the schematic here with the VS pinout)

Assuming that the lamp detection is on the "cold" end, this wiring scheme can be expected to have the lamp detection problem. So i didn't test it, i modified it right away. Since the original ballast was essentially a "self ballasted CFL" sort of ballast, i guess that it would actually work with the wiring above just fine



Anyway, i rewired it to :


And it does exactly the problem i tried to avoid....



I took the lamp sockets off the gear tray and plugged them on the lamps freely. Then i connected power to ballast and EM pack at once, to recreate the "not working" condition. And then, i took off and connected back one socket at a time. to see which socket disconnect/connect triggers the ballast's inserted lamp detection. Result : The ballast detects the lamps on the cold end (terminals 1/2/3)

So, when the EM pack reconnects the lamp (a split second after power applied) the lamp is not detected. If then, i take off and put back on the socket on the same lamp end (same as where the EM relay is), then it does detect the lamp

Also, it does detect the lamp and start if the cold end of the lamp is inserted by hand when the ballast is powered on (few seconds after power applied, unlike few 10's mSec ? with the EM relay)



I tried to exchange the lamp roles on the ballast (swap terminals 2-3, 4-6, 5-7) to see if the other lamp's circuit does not have this glitch, but it have it as well



I guess that it is a glitch of the ballast's lamp detection logic, which can't be resolved except by playing with timings (add transistor with RC delay in series with the relay coil in the EM module ? or increase the value of some "+ main electrolitic cap to chip Vcc" initial startup resistor in the ballast ?)

Would like to read your input on the matter

Single pole relay EM pack need a double type. This is meant for switch start circuits.
Also a lot of the EM packs here have ballast and out with a small delay to stop this.

Yes, the ones I've just been fitting have the in / out terminals for mains supply to ballast for this very reason. Important to use that terminal set for HF applications. You don't need to wire to that terminal set when used with switch start.

This is a double pole relay

How would an EM with only one relay pole work for Switchstart ? There are 2 disconnects to be made for EM operation - the lamp must be disconnected from the line (on one pole) and from the starter loop (on one pole)



The 5 wire EM packs are meant for HF and Magnetic ballast compatibility - The older ones had 4 wires, without the 2 terminals that have to be jumpered when used with Magnetic (bringing the jumper to the outside was the change that made it possible to use with HF). Some manufacturers are too lazy to draw the HF wiring, but this does not mean it is not meant for HF

The 5 wire scheme is based on that HF ballasts detect lamp insertion on the cold end - So if wired with the relay disconnecting that, it is expected to work fine. And it does with pretty much all HF ballasts i seen, until this one. If wired in reverse - with the relay on the hot end - then yep, it does the lamp detection problem with many ballasts (except the cheap Chinese ones, since they dont have any lamp detection logic whatsoever)

So i guess it is some glitch with this specific ballast. (Maybe it is somewhat common, so thats why there are the EMs with the ballast input power disconnect you talk about, but i havent seen anything like that)



I'll see if there is an issue in this case (whether the user is bothered by having to flip the switch to restart the light), if yes, then i will hack at it some more. (Try to add some delay in the EM pack itself, or make a proper sequence circuit with 2 small external relays with 230V coils)