Module cascade



Wiring: The module reserves a 2.54mm-3P pad for cascading. The user can first solder

the 3P bent header and then use the Gravity 3P digital sensor cable for connection.

Insert one end of the cable, PH2.0-3P white male connector, to the PH2.0-3P white

female connector of the module, and the other end, black 2.54mm-3P female header

connector, to the 3P bent header of the previous module. Connect the modules in such

way one by one to forming a string of lights. As shown in the figure below, the "+", "-",

and "DO" are connected to "+", "-", and "DIN" respectively of the next module.



Code: The sample code applies to a single module. To use in cascade, you need to

change the value "1" in the sample code (as shown below) to the number of modules to

be cascaded. Otherwise no matter how many module is cascaded, only the first one will

light up. For example, a RGB LED strip is made up of 32 modules. The value should be

changed to "32".

 #define NUM_LED 1     // Number of LEDs in a strip 



Power consumption and length estimation: The length of every section of a RGB LED

string (Module + Gravity 3P Digital Sensor Cable) is about 32cm, which greatly

reduces the number of LEDs and power consumption per meter compared to the

ordinary RGB LED strip. Under the same power supply, the entire strip can be extended

to several tens of meters. If modules are powered by 5V, set to white color and brightest,

power consumption can be up to 48mA. Under this condition, if the strip is powered by

the USB of the Arduino whose maximum output capacity is 500mA (determined by the

Arduino internal self-recovery fuse). Such configuration can drive about 10 modules with

a total length of about 3.2m. If the Arduino is externally powered by 7-12V (using a

power adapter, 2s 7.4V or 3s 11.1V lithium battery), its maximum output capacity is

800mA (determined by Arduino internal LDO). Such configuration can drive about 16

modules with a total length of about 5m. If the Arduino is externally powered by IO

sensor expansion board V7.1 , where the servo external terminal SERVO_PWR is powered

by 5V 2A AC adapter, such configuration can drive 48 modules with a length of about

13m. The estimation above provides the lower limit (worse case) of the cascading

number from the perspective of the supply current and the maximum power

consumption of the module. The actual maximum cascading number is affected by the

actual power consumption (color or brightness) and the voltage loss in cable (the

voltage is dropping through the cable). Usually, the power supply voltage of the last

module of the string should not be lower than 3.3V. The number and length of the

cascade can be much higher than the estimated value above. By properly decreasing

brightness, the maximum cascading number can be greatly increased.