RAPIX DALI-2 PIR sensors are listed as 2 mA current draw from DALI.
This is incredibly low.
Are we serious? Is this for real? How do we do it?
RAPIX DALI-2 Sensors & the DALI-2 requirements
DALI-2 Certification is managed by the DALI Alliance. The testing & submission guides used for certification set out the methods used to declare current draw of a DALI-2 product.
The measurement methods are moderately complex, but are summarised as:
Declared current is the peak current drawn by the product, including during an initial power on period.
We measured our DGOZ-SEN-PRSW sensor to confirm the current it uses. For the method we used, the measurement uses the voltage developed over a 100 ohm sense resistor. If this resistor has 1 mA passing through it, then by ohms law there will be 0.1 V developed across that resistor.
The image shows that after power up, the sensor draws 2 mA for a period of time, and then settles down to its static or idle current of around 0.75 mA.
Because we need to declare the peak current, the sensor is rated as 2 mA. For most of its normal operation, the actual current used is much lower.
Use of DALI Current by a Product
Manufacturers have different approaches to electronic design of a DALI product.
A consequence of these differences are:
- Some products will have a constant current draw under all conditions (for example: there are sensors that consume 8 mA always)
- Some products will have a variable current draw – taking less from the DALI line if less current is needed.
An easy way to test which of these approaches has been used is to power the DALI product from a DALI power supply, with an ordinary digital multimeter in series. In this condition the DALI line should have no communication, enabling a measurement of the idle or static current consumption.
If this measurements is significantly smaller than the declared current in the product data sheet, then the manufacturer has a design that uses lower current when the full declared current is not needed.
RAPIX DALI-2 sensors have a peak current limited to 2 mA, and typically show a static current draw from the DALI line of between 0.7 mA and 1.0 mA.
DGOZ-SEN-PRSW running from a RAPIX DALI-2 power supply of nominally 18V output. The static current is shown as 0.78 mA.
To show the static current for a lower bus voltage, we put a resistor (and had to use a resistor box) in series. We got the bus voltage down to about 10V. This show the static current draw of the sensor at 0.73 mA.
Although not shown here, the sensors with light level measurement (such as DGOZ-SEN-PRLLSW) have the same peak current draw of 2 mA, and a slightly higher static current consumption.
Typically, these sensors will use about about 0.8 to 0. 85 mA as the static (idle) current consumption.
These currents are very low. How do we do it?
Ozuno has been an expert in extreme low power electronic design for two decades, and the senior designers have been working on low power electronics for over 30 years.
The DALI-2 sensors build on this long expertise. To get ultra-low power consumption, five separate techniques were needed. Only when put together could we get a super-low power product.
Of course, we won’t disclose the “secret sauce”!
Getting to this point
RAPIX sensors have been through a product evolution over a 7 year period:
- Initial release (non-DALI-2);
- Various improvements for manufacturability; and finally:
- DALI-2 version – which includes a major electronic re-design that significantly reduced the current compared to earlier generations.
To make it easy for customers the product order codes were not changed during the product history.
DALI-2 versions have the DALI-2 logo on the product label.
Versions Prior to the DALI-2 Release
RAPIX DALI sensors before DALI-2 certification were not governed by any certification process or test method.
On those earlier versions:
- The current declared was an average measurement, which was typically around 1.8 to 1.9 mA and declared as 2 mA in the data sheet.
- The peak current draw was typically 3 to 4 mA, and in some circumstances was higher for short periods of time.
Those earlier pre-DALI-2 sensors also included a recommendation to have no more than 20 pcs per DALI line. When installed within those limits, and with typically 50 luminaires per DALI line, the nature of the peak and average currents saw satisfactory operation.