Repairs to fog machine

[partyanimallighting]

Sorry, I didn't read your question properly.

I think it's quite possible that a pump could be faulty in a way that causes it to barely run at all when powered from a phase controlled signal at, say, 50% power, while it would still run at full speed if powered from a 100% AC signal. So if a suspect pump performs the same as a known good pump when they're both powered directly from 110V, that doesn't necessarily mean that the suspect pump will perform the same as the known good pump if they're both driven from the board.

Hi Kris, I normally use these units hooked up to a DMX lighting controller and, when I push up the controller slider that corresponds to the fog machine, the machine outputs. If I put the slider at 25%, 50% or 100% the fog machine outputs accordingly. The remote control however, has UP and DOWN buttons to adjust the output percentage and another button that has a "POWER BURST" feature. You mentioned that the pump could be faulty in a way that would cause it to output less but these pumps are really simple so I drew up a diagram as to their internal layout and included an image of a similar pump. There aren't a lot of parts that can cause issues but maybe you could point out something I'm missing.

 

[KrisBlueNZ]

I don't know much about pumps, so I can't tell you specifically what problem might cause a pump to run fine at full-cycle 110V AC but run very poorly at 50% phase-angle-controlled supply, but I think it's quite possible that it could. That pump is probably not designed to run from a phase-angle-controlled source. Phase angle control is normally only used for incandescent lamps.

Obviously the manufacturer of that fog machine has tested some new pumps and found that they worked OK with a phase-angle-controlled supply, but I have no problem accepting that some types of deterioration (perhaps even deterioration caused by running from a phase-angle-controlled supply in the first place) could cause the pump to run poorly from a phase-angle-controlled supply.

If you understand how the pump works internally, you may be able to guess why it wouldn't work properly from a phase-angle-controlled supply. Instead of receiving a steady sinewave, which would make the magnetic field around the coil vary smoothly, it would receive a voltage that's zero, then suddenly jumps up, then follows the sinewave shape for the rest of the half-cycle, then goes to zero again, then suddenly jumps up in the other direction, and so on. Try to imagine how that would affect the pump's operation.

That's all I can really say on the matter.

 

[partyanimallighting]

I don't know much about pumps, so I can't tell you specifically what problem might cause a pump to run fine at full-cycle 110V AC but run very poorly at 50% phase-angle-controlled supply, but I think it's quite possible that it could. That pump is probably not designed to run from a phase-angle-controlled source. Phase angle control is normally only used for incandescent lamps.

Obviously the manufacturer of that fog machine has tested some new pumps and found that they worked OK with a phase-angle-controlled supply, but I have no problem accepting that some types of deterioration (perhaps even deterioration caused by running from a phase-angle-controlled supply in the first place) could cause the pump to run poorly from a phase-angle-controlled supply.

If you understand how the pump works internally, you may be able to guess why it wouldn't work properly from a phase-angle-controlled supply. Instead of receiving a steady sinewave, which would make the magnetic field around the coil vary smoothly, it would receive a voltage that's zero, then suddenly jumps up, then follows the sinewave shape for the rest of the half-cycle, then goes to zero again, then suddenly jumps up in the other direction, and so on. Try to imagine how that would affect the pump's operation.

That's all I can really say on the matter.

Hi Kris, strangely enough, all the major fog machine use this type of pump, from the low end Chinese to the high end European manufacturers so the pumps are probably considered stable enough I suppose. When you speak of deterioration, do you mean actual wear and tear on the physical moving parts? Or deterioration of the electrical solenoid that moves the pump piston up and down? Anyway, that's the end of this particular problem and, despite my initial wrong diagnosis in the beginning, I did learn a lot from you guys. So thanks once again for all your help.

 

[KrisBlueNZ]

Hi Kris, strangely enough, all the major fog machine use this type of pump, from the low end Chinese to the high end European manufacturers so the pumps are probably considered stable enough I suppose.

Do you know whether the other fog machines drive their pumps with a phase-angle-controlled supply? They could drive it with a full cycle supply with variable voltage. This would be a lot harder to generate. Is the fog machine you're working on a cheaper product than the others? Maybe they made a design compromise.

When you speak of deterioration, do you mean actual wear and tear on the physical moving parts? Or deterioration of the electrical solenoid that moves the pump piston up and down?

As I said, I don't know much about pumps. My guess would be mechanical. When you reconditioned the suspect pump, and got it working as it should in that unit, what did you do to it? At least one of the things you fixed could have been a factor in making it run slow with the phase-angle-controlled supply.