UV flame scanner bulb used as safety-need circuit help

Discussion in 'The Projects Forum' started by Rezaxis, Aug 27, 2006.

  1. Rezaxis

    Thread Starter New Member

    Aug 27, 2006
    1
    0
    I have a flame scanner made by UV-eye, just the bulb part. It consists of a UV sensor bulb with a 1K resistor (looks like 1/2 watt) on each leg, and two 600V wires/leads. As far as I can determine, it takes a minimum of 560VDC to make it conduct. I think it's rated at 600V, it's suggested that 600V rated wire be used to connect it. But I don't know the current ratings. UV Eye part number 4-314-1 for the bulb and UV1a is the part number for the scanner assembly. I can't find any other info.

    As far as the bulbs operation: It has a rarified gas inside. If enough voltage is applied the bulb "avalanches" (conducts then opens) repeatedly depending on the intensity of the UV it senses. The more flame (UV), the more pulses per second. I found a similar circuit using a different product at the following link, if that helps

    http://www.superdroidrobots.com/product_info/R2868.pdf

    If anyone looks at that link and sees the circuit, can you tell me what the two capacitors that parallel the input and output do? The bulb I have doesn't seem to have a cathode/anode designation on it, or any other markings either. It doesn't look polarized to me.

    I can supply the the whole safety circuit with 120VAC at 9.5A. I want to use it as a one safety to interupt 120VAC going to an emergency gas shutoff valve that requires 120VAC at 0.12A to remain open. For my application I just need to know if a flame is present or not. I would like to be able to bypass this flame sensor, it's output or the controlling device, during initial startup (the emergency gas shutoff valve must be open, supplied with 120VAC, but no flame would be present till I manually light it, after which I would manually switch the UV scanner into the circuit so it acts as a safety.)

    I would also like to put the UV scanner (flame on/off) safety in series with an omni-directional tilt switch of some kind that would open the 120VAC going to the same gas shutoff valve. So, if the flame goes out the gas shuts off, or if the unit tips the gas shuts off.

    I got suggestions for a micro tilt switch on another forum. It only works after a tilt of 45 or more degrees. I need something more sensitive and without need for digital electronics. I want to keep this as simple as possible, so I am looking for a normally closed omni-directional mercury tilt switch that will handle the current requirements of the emergency gas shut off valve.

    So, in a nutshell if I got it right, it looks like I have to step up 120VAC to 1200VAC (can I use a 120V/12V transformer backwards? Can I get enough current out of it?) rectify and filter to 600VDC, apply this with proper current limiting to the bulb(I'm at a loss here), voltage divide properly, then filter the scanners output pulses and somehow control a devise (relay?) that would interupt 120VAC to the emergency gas shutoff valve.

    I don't have my electronic test/build stuff anymore, but I still got a meter and soldering iron! :) I've been out of school a looong time (1982), and haven't messed with electronic stuff in a long while either and I have forgotten A LOT, but if you kind people could lead me I can most certainly construct anything you might dream up. I DO need help here. Remember, "Cheap fart" is my middle name! You can call me that, I don't mind!:p

    Oh! and I'm a new forum member so Hi everyone and thanks to all who look and many thanks to any one who might help.

    Rez(cheap fart)axis
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    This is obviously a safety-related project. A very strong suggestion is that you obtain components with known operating characteristics. The Hamatsu flame sensor might be a good start, as it amy be had with a circuit board that will supply it with the correct voltage, and pass the signal on to the shut-down circuitry.

    With respect to the tilt sensor, the same applies. get some straight stuff that comes with descriptive literature. Understand what you are attempting to do, or else purchase a turn-key system that carries a warranty.
     
  3. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Hi,

    You just mount the tilt switch at an appropriate angle to get it "more sensitive" or rather biased.
    If you can get your hands on a mercury switch these days, just mount it to get the action (n.o. or n.c.) that you want.

    But I'll second the notion that you shouldn't play around with unknown components, especially since you state that it's a safety circuit and that you're not that well versed in the arts !
     
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