CSTP Voltage Present when in Relay Mode and circuit set to 0
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Symptoms/Issue
I have plugged some LED lamps or Mirror Ball Rotator into my Sensor Thru Power Modules, or CSTP circuits, in relay (switched) mode, but they don't turn off.
When testing circuits with a multimeter I'm detecting voltage but you have confirmed the circuit is set to 0.
Where does this voltage come from?
Description/Explanation of Issue
In Europe, or in power control systems that are designed for Europe, it is common that you might detect voltage on a circuit with a multimeter - commonly this would be the incoming voltage to the system but could be seen as any value between 0 and the incoming voltage.
This is completely normal and expected.
The reason for seeing this is any circuit with a dimmer (and this will include any Thru Power racks or modules) must include suppression capacitors so that the system complies with the EMC regulations. These are connected in each circuit and sometimes within the rack as well.
Because these are in the circuit, they allow for a very small amount of leakage to pass through, and because the circuit is not completed your multimeter will detect that.
When a tungsten load is connected to this circuit you will measure no voltage as the circuit is completed and there is a load in line.
Because tungsten is a resistive load this works as expected and the load does not turn on at 0%.
However capacitive loads such as LED drivers/lamps or very small motors like mirror ball rotators may still turn on.
Tiny mirror ball rotators need so little power to spin, that just the power going through the suppression capacitors will mean they can spin.
Loads with switch mode power supplies or capacitive loads can be affected in different ways:
The 2 mains things you might see is the Load never turning off, either stuck at full if the load is really small, or the load is only only dimming down to a low level.
Or you might see your loads flash - this will be the capacitors in the load switch mode power supply slowly charging up from the leakage.
Once they have enough charge they will turn on briefly, using up all the power they charged up.
They will not be able to maintain a powered state as the leakage through the EMC capacitor only supplies a tiny amount of power and then start charging again.
Why does this still happen if I put my ThruPower circuit into Relay mode?
In a ThruPower system the circuit is the same up to the SCR or Triac - but when in relay mode, the relay clicks on instead of the dimming circuit turning on, so the power flows through the relay and then back out of the same terminals. The dimming circuity (including the suppression capacitor) however is not taken out of line when in relay mode.
Fix/Solution
- In some modules or systems it is allowed to take out the suppression capacitors as long as the load is small, see links below for details.
- If using Sensor racks, use a true relay module as this will not have the suppression capacitors.