So today we realized a dimmer in our floor pocket wasn't working. Later we figured out the breaker was just tripped. But, while trying to figure out why my light wasnt coming on, I busted out my Multimeter and tested it and got 0 volts. So I thought I'd try the other dimmer in the floor pocket and make sure my multi meter was working just fine. Well in the other floor pocket, my meter read 66.9 volts. And after we flipped the breaker back on the original circuit, my meter read regular voltage. So my question is what could cause that one dimmer to be 67 volts? Both dimmers I tested are in the same module. And the CEM said they were both okay.
67 Volts?
- Thread starterShawncfer
- Start date
Do you have dimmer doubling?
epimetheus
Well-Known Member
JD
Well-Known Member
The SSR firing circuit allows some voltage to pass even when the dimmer is at 0 if there is no load on the dimmer. If you measured one dimmer that had no load, that dimmer would show voltage, if you measured the same dimmer with a load plugged in, you would get 0 volts (unless the low end trim is set high.)
I am actually surprised it was only 67 volts, but depending on the layout of the firing circuit, this reading will change a bit. I suspect the "0" dimmer had another load on it somewhere.
Note: FYI- In the case of an SSR, the post-opto circuit is part of the molded SSR power cube. On older SCR and Triac dimmers, the circuit is external. Bottom line, on an SSR dimmer, you will not see this circuit that allows the bypass on the schematic as it is part of the SSR component itself.
I am actually surprised it was only 67 volts, but depending on the layout of the firing circuit, this reading will change a bit. I suspect the "0" dimmer had another load on it somewhere.
Note: FYI- In the case of an SSR, the post-opto circuit is part of the molded SSR power cube. On older SCR and Triac dimmers, the circuit is external. Bottom line, on an SSR dimmer, you will not see this circuit that allows the bypass on the schematic as it is part of the SSR component itself.
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We don't
It is not. However it was able to read other circuits just fine and this one was being bumped to full on the board. And in the patch (ETC Express), the channel wasn't already assigned a maximum level.
When I measured other dimmers that were off I still got a reading of 0 Volts. And when we would turn them on I would get 120 volts. It was the same for the original floor pocket once we flipped the breaker. The problem floor pocket, however, would read 0 Volts when of and 67 Volts when bumped on.
Woah, you totally lost me there.
JD
Well-Known Member
We think of the SSR (Solid State Relay) as a part. Often called a "power cube." The SSR however is actually a circuit composed of a couple of SCRs, a photo optic isolator, and a handful of resistors, capacitors, and other parts all potted in an epoxy block. On the outside, it is a cube that mounts to a heat-sink with input and output terminals, but there is a lot inside. Some of what goes on inside allows some voltage to pass at a very low current. Under normal conditions with a load attached you will not see this leakage, but it is why we get crazy voltage readings from dimmers that have no load attached. It is normal and does not indicate a defect. It is also why you should flip off the circuit breaker before you can be sure there is no output voltage.
If you turned on the circuit and the lamp only went to half brightness and that is when you got the 67 volt reading, It would indicate one of two problems:
1) A gating failure inside the SSR is only operating one of the SCRs inside the cube.
2) It is an ETC dimmer that accidentally got switched into dimmer-doubling mode and is only turning on one of the two SCR's inside the cube.
In either case, the reading should be closer to 77 volts, but due to meter limitations may be giving you the 67 number.
One other note: When there is no load on the dimmer, you may get an arbitrary output reading when the dimmer is full on as there is really not enough current in the circuit to latch the SCRs when they are gated. This may vary among SSRs just due to parts tolerances.
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