DMX Relay
- Thread startertschnuckel
- Start date
chawalang
Well-Known Member
Something may have been lost in translation
You are looking to turn the bubble machine on and off?
You are looking to control the bubble machines rate at making bubbles?
As far as power you do not want to connect solid state electronics to a dimmer parked at 100%, it will damage various components over time. You want it plugged into a non dimmable 20 amp circuit for power, a la a relay tray in a sensor rack or a wall plug.
As far as control does it have 3 or 5 pin on it? You should be able to control the various attributes using desk channels.
Is there a specific reason you want to use a DFD Relay? That unit is not a dimmer.
You are looking to turn the bubble machine on and off?
You are looking to control the bubble machines rate at making bubbles?
As far as power you do not want to connect solid state electronics to a dimmer parked at 100%, it will damage various components over time. You want it plugged into a non dimmable 20 amp circuit for power, a la a relay tray in a sensor rack or a wall plug.
As far as control does it have 3 or 5 pin on it? You should be able to control the various attributes using desk channels.
Is there a specific reason you want to use a DFD Relay? That unit is not a dimmer.
GreyWyvern
Well-Known Member
The key there is dimmer. It will be fine on a relay pack in a dimmer rack, just not a dimmer pack in a dimmer rack, even if the dimmer is set to 100%/non-dim/switched/etc. because the dimmer messes with the AC sine wave and could damage the power supply.
How handy are you? How about this:
http://northlightdmx.com/dmxtorelay.htm
http://northlightdmx.com/dmxtorelay.htm
tschnuckel
Member
That might be a good option since I can solder. It seems like there would be more options for a relay.
I've got a carpet dryer that I wish I could put DMX on too. CITC or Antari does on their fans, so the speed could be controlled. 1200 bucks seems like a lot for a $200 fan. Especially when my ION was 7k and does way more.
coldnorth57
Active Member
porkchop
Well-Known Member
What kind of dimmer racks do you have? Many manufactures have relay modules that can be swapped with the dimmer modules already in the rack. This allows you to use the existing power and data runs while providing the mains power that many devices need.
Also if that doesn't work or is too expensive Blue Point Engineering makes a variety of DMX goodies at a reasonable price.
Also if that doesn't work or is too expensive Blue Point Engineering makes a variety of DMX goodies at a reasonable price.
kicknargel
Well-Known Member
I had a thread about similar issues. I too had trouble finding a reasonable 120v DMX relay. I ended up using DJ dimmer packs, but my use was short-term and I didn't really care if I burned out my electronics. One thing that was suggested was using a cheaper 12v DMX relay to drive a second beefier relay controlled by the 12v.
tschnuckel
Member
Didn't think think about doing it that way.
Les
Well-Known Member
If it's just a bubble machine, that's basically just a fan and "rotisserie" motor, correct?
The problem I've seen with motors on dimmers is when you get it down to stall-out voltages. The motor continues to receive power but sits there and bakes instead of dissipating the energy the way it should.
I doubt you would have a problem in relay mode.
Goes against what the manual said, though. Either there is something in there that can be hurt, or they included the passage as "blanket" protection and to reduce troubleshooting calls.
The problem I've seen with motors on dimmers is when you get it down to stall-out voltages. The motor continues to receive power but sits there and bakes instead of dissipating the energy the way it should.
I doubt you would have a problem in relay mode.
Goes against what the manual said, though. Either there is something in there that can be hurt, or they included the passage as "blanket" protection and to reduce troubleshooting calls.
Last edited:
David Ashton
Well-Known Member
A little long, and a little technical... but, if you want to know exactly what you can do, what you can't do, and the underlying reasons why, read on.
(Hopefully this dispels any myths, but also prevents people from "doing something dumb" and regrettable, or doing something unsafe for those of you who like to "jump in the deep end" and get into the electric/electronic circuits.)
The issue with "dimmers set to 100%" to power anything other than lights is their TRIAC (or double SCR) triggering gets a little funky if the load has a complex impedance. (That is, if the voltage waveform and current waveform do not remain in-phase.) Incandescent light bulbs have a simple "ohmic resistance" with no complex roots, so they're fine. Motors and "imperfect" transformers naturally present a load impedance with an inductive component; linear and switch-mode power supplies often present a load impedance with a capacitive component. These complex impedances can cause the TRIAC or SCRs in the dimmer to chop up the sinusoidal AC power wave at some point before or after the zero crossing (even if set to 0% or 100%), leaving you with "dirty power" that's not really very sinusoidal anymore. This can have a number of implications:
"Power factor corrected" devices try to minimize the complex part of the load impedance, so they behave more like a simple resistive load. That being said, if your bubble machine, fan, or whatever else you want to control has a power factor of 1 (or very close to it), running it from a dimmer that you can guarantee will stay at 100% (or 0%) is fine. Trouble is, few products list their power factor in the specifications.
If you have access to an oscilloscope, you can clip it to the AC power output from the dimmer and check if the voltage tracks a fairly "clean" sinusoid when you connect your bubble machine, fan, whatever. (To do this safely and properly, you need an oscilloscope with at least 2 input channels, and set it to display the "difference" between the channels. Then use attenuating probes on both channels, specifically designed for measuring high voltages. Clip one probe to the AC Live, and the other probe to the AC Neutral, and set the oscilloscope sweep oscillator to trigger either at the measured zero crossing (which always works), or synchronized to the oscilloscope's own AC power (which works if you're powering it from an AC source at the same frequency as the dimmer -- nearly always the case). (There is a way to do it with single-channel oscillopes too, but it's dangerous if you don't know what you're doing and if anyone else is around who might touch things, so I'm not going to encourage it.))
Strange enough, if the power is not nice and smooth, you might actually be able to "clean it up" and get the "chops" closer to the zero crossings by turning down the dimmer level slightly! (It doesn't seem intuitive -- more power at less than 100%, but slight power drop as you approach 100%? But depending on the dimmer's triggering circuit, and the load's complex impedance, this can sometimes be the case! Especially since the trigger system of many dimmer circuits is effectively in series with the load, and therefore the V-I phase offset of a complex load impedance affects the phasing of the dimmer's trigger!)
Interestingly, variable speed controls for ceiling fans and variable-speed electric drills actually operate the exact same way as light dimmers do! How do they do it without damage? They limit the range of their trigger point to keep it close to the start of the half-cycle, so the motor never stalls. (Or as a more intuitive concept, they "only operate in a small upper range".) Their trigger circuit is also not too-badly affected by the motor inductance. And their TRIAC is rated to handle voltages a fair bit higher than nominal AC peak. Ceiling fan controls also initially turn on the power at "100%", so the motor gets enough start-up torque before the operator will likely turn down the speed. (And in both cases, the motors are also designed so a little phase-chopping won't hurt them.)
So if you have a carpet dryer or fan or whatever which you want to run at variable speed, the answer may not necessarily be a definitive "no"! Look into its motor design, and the design of the dimmer you intend to use, and how the two interact. If the device has separate control electronics with their own power supply (and you don't mind voiding its warranty and modifying circuits), you can usually disconnect that from the motor's supply and run it off a separate "clean" continuous AC power line. (If there are heating elements though, you don't want to reduce the air flow over them when they're in use! Best bet is to disconnect any heating elements if you're going to be monkeying around with variable air flow rates.)
(Hopefully this dispels any myths, but also prevents people from "doing something dumb" and regrettable, or doing something unsafe for those of you who like to "jump in the deep end" and get into the electric/electronic circuits.)
The issue with "dimmers set to 100%" to power anything other than lights is their TRIAC (or double SCR) triggering gets a little funky if the load has a complex impedance. (That is, if the voltage waveform and current waveform do not remain in-phase.) Incandescent light bulbs have a simple "ohmic resistance" with no complex roots, so they're fine. Motors and "imperfect" transformers naturally present a load impedance with an inductive component; linear and switch-mode power supplies often present a load impedance with a capacitive component. These complex impedances can cause the TRIAC or SCRs in the dimmer to chop up the sinusoidal AC power wave at some point before or after the zero crossing (even if set to 0% or 100%), leaving you with "dirty power" that's not really very sinusoidal anymore. This can have a number of implications:
- If the "positive" half-cycles are chopped asymmetrically compared to the "negative" half-cycles, the AC power going to your device will effectively have a "DC bias". This can cause the core of your device's motor or power supply transformer to magnetically saturate, then draw excess current, and overheat. (I've never seen this happen on a dimmer at 100%, but I've seen melted transformers from being placed on dimmers at <100%.)
- If the half-cycle chopping is offset significantly far from the zero crossings, the transformer or motor back-EMF can cause high-voltage spikes to appear on the coils (which can damage the dimmer's TRIAC or SCRs), and in the case of transformers, also induce spikes on the secondary coils (which can damage your device's internal electronics). (I've never seen this happen on a dimmer at 100%, but I've seen (and repaired) dimmers that got damaged from this while running at <100%.)
- Also if the half-cycle chopping is offset significantly far from the zero crossings, the motor or transformer will start to behave like a choke and impede the current flow. For devices with linear power supplies, this can cause a "voltage sag" in the power rails inside your device (from which its internal electric/electronic components are powered). (This makes sense, because "chopping the wave far from the zero crossing" is exactly how dimmers reduce the power going to a lamp! Only in this case, the reduction is a little more pronounced.) For switch-mode power supplies (which have a feedback loop), this can cause the power supply to draw excess current in an attempt to maintain proper internal system voltage. And for motors, this can significantly drop the torque, which reduces the motor's intended "regulating" back-EMF, causing it to draw more current (even though the motor appears to have "less power").
"Power factor corrected" devices try to minimize the complex part of the load impedance, so they behave more like a simple resistive load. That being said, if your bubble machine, fan, or whatever else you want to control has a power factor of 1 (or very close to it), running it from a dimmer that you can guarantee will stay at 100% (or 0%) is fine. Trouble is, few products list their power factor in the specifications.
If you have access to an oscilloscope, you can clip it to the AC power output from the dimmer and check if the voltage tracks a fairly "clean" sinusoid when you connect your bubble machine, fan, whatever. (To do this safely and properly, you need an oscilloscope with at least 2 input channels, and set it to display the "difference" between the channels. Then use attenuating probes on both channels, specifically designed for measuring high voltages. Clip one probe to the AC Live, and the other probe to the AC Neutral, and set the oscilloscope sweep oscillator to trigger either at the measured zero crossing (which always works), or synchronized to the oscilloscope's own AC power (which works if you're powering it from an AC source at the same frequency as the dimmer -- nearly always the case). (There is a way to do it with single-channel oscillopes too, but it's dangerous if you don't know what you're doing and if anyone else is around who might touch things, so I'm not going to encourage it.))
Strange enough, if the power is not nice and smooth, you might actually be able to "clean it up" and get the "chops" closer to the zero crossings by turning down the dimmer level slightly! (It doesn't seem intuitive -- more power at less than 100%, but slight power drop as you approach 100%? But depending on the dimmer's triggering circuit, and the load's complex impedance, this can sometimes be the case! Especially since the trigger system of many dimmer circuits is effectively in series with the load, and therefore the V-I phase offset of a complex load impedance affects the phasing of the dimmer's trigger!)
Interestingly, variable speed controls for ceiling fans and variable-speed electric drills actually operate the exact same way as light dimmers do! How do they do it without damage? They limit the range of their trigger point to keep it close to the start of the half-cycle, so the motor never stalls. (Or as a more intuitive concept, they "only operate in a small upper range".) Their trigger circuit is also not too-badly affected by the motor inductance. And their TRIAC is rated to handle voltages a fair bit higher than nominal AC peak. Ceiling fan controls also initially turn on the power at "100%", so the motor gets enough start-up torque before the operator will likely turn down the speed. (And in both cases, the motors are also designed so a little phase-chopping won't hurt them.)
So if you have a carpet dryer or fan or whatever which you want to run at variable speed, the answer may not necessarily be a definitive "no"! Look into its motor design, and the design of the dimmer you intend to use, and how the two interact. If the device has separate control electronics with their own power supply (and you don't mind voiding its warranty and modifying circuits), you can usually disconnect that from the motor's supply and run it off a separate "clean" continuous AC power line. (If there are heating elements though, you don't want to reduce the air flow over them when they're in use! Best bet is to disconnect any heating elements if you're going to be monkeying around with variable air flow rates.)
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