Need help with Relay for auto start CX-900 Lamp House

[Frank Raia]

I have a Cinemeccanica CX-900 lamp house and would like to make it auto strike so I can use it with my TA-10 automation. The manual has a section about adding a relay. I found the relays on ebay but there are 2 different ones. I take it I need the 24v dc one? Or the AC one?.

Also the relay schematic page has a auto/manual switch. I can not find the switch anywhere in the lamp house. Anyone know the location? Do I have to add one?

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[Mark Gulbrandsen]

I never liked the sensitivity adjust pot. I always changed those over to a zener diode version. With the potentiometer, when the AC line voltage sags, especially in Summer, often you will still have to hit the manual strike button anyway. Check out the manual for the Super Lumex on page 23. Strong used a zener diode instead of the pot.

[Frank Raia]

No one? Where are you guys?

[Ryan Gallagher]

The document reads like you are installing the auto/manual switch too to "upgrade" to a unit capable of automation. One would not necessarily want a lamphouse that could "only" be fired via automation, so I think the switch is added in this setup. If the lamphouse has no switch currently assume it only does "manual" operation as configured. Any old two position switch should work as I don't think that line will be related to the high voltage/current at all? But if you want to play it safer, a plastic rocker switch rather than a metal flip switch.

Most of the Strong lamphouses has a manual/console switch if you need to reference another design manual to understand the concepts better.

I don't have any advice on the relay question.

[Ryan Gallagher]

Though I suppose on the AC vs DC relay question. The document does say "P.B. KRP 11 DC Relay with polarity protective diode"... DC seems to be your answer there.

[Frank Raia]

Ryan, thank you. I can add a switch but the relay is the problem. I wish the manual stated the voltage because there are multiple voltage relays listed as KRP 11 DG. Also I guess I will have to add the diode myself as the relays dont have them inside. I did email cinemeccanica, but Im sure they wont answer about a product that is over 50 years old.

[Ryan Gallagher]

Ryan, thank you. I can add a switch but the relay is the problem. I wish the manual stated the voltage because there are multiple voltage relays listed as KRP 11 DG. Also I guess I will have to add the diode myself as the relays dont have them inside. I did email cinemeccanica, but Im sure they wont answer about a product that is over 50 years old.

It was a bit hard to read, I read that as "DC"... but maybe the part numbers you are finding are in fact "DG" there.

[Josh Jones]

I had the same lamp. I installed a 75v zener in series with the coil. Be sure to put a ceramic bypass across the zener to protect it from ignition transients. The lamp will then auto strike when the bulb voltage hits about 90 volts.

Alternatively, you can swap out the relay for a 120vdc one and place the coil directly across the lamp supply. Ac relays can be used, but they need a lot of resistance between them and the supply feeding them or the coil will overheat. Dropout voltage is also very low, maybe 10% of RMS coil voltage.

[Frank Raia]

I had the same lamp. I installed a 75v zener in series with the coil. Be sure to put a ceramic bypass across the zener to protect it from ignition transients. The lamp will then auto strike when the bulb voltage hits about 90 volts.

Alternatively, you can swap out the relay for a 120vdc one and place the coil directly across the lamp supply. Ac relays can be used, but they need a lot of resistance between them and the supply feeding them or the coil will overheat. Dropout voltage is also very low, maybe 10% of RMS coil voltage.

Josh, This is the Relay I purchased. In your opinion will this be okay or do I need a different voltage? krp11.jpg

[Josh Jones]

That should work.

[Frank Raia]

That should work.

Josh, so the diode would go across pin 2 and 7 correct? What would happen if no diode?

[Josh Jones]

Using a 110VDC relay, the diode is not needed. Connect the coil across the lamp supply terminals in the lamphouse.

[Frank Raia]

Using a 110VDC relay, the diode is not needed. Connect the coil across the lamp supply terminals in the lamphouse.

I'm sorry to be a pain, I don't understand what coil?

[Josh Jones]

Connect terminal 2 of the relay to +, terminal 7 to -. Wire the normally open contact to your igniter, the common to AC line.

[Frank Raia]

Connect terminal 2 of the relay to +, terminal 7 to -. Wire the normally open contact to your igniter, the common to AC line.

Isn't that what the relay is doing?