#818 CHA-81 LED Matrix Soldering Kit

Building the CHA-81 LED Matrix Soldering Kit and investigate the principles of operation. A simple design that offers endless hours of fiddling!

Here’s a quick demo..

Notes

I first saw this kit on Julian Ilett’s YouTube channel (see video links below) and immediately had to find one to play with!

The kit basically runs an X and Y ripple counters that drive a 9x9 LED array. Speed adjustment and directional controls make this a wonderful time-sink.

I suspect it may originally be a design from ICStation

Kit Details

I found “CHA-81 DC5-9V LED Tracking Light DIY Parts Electronic Production Kit 9X9 Dot Matrix Display” (aliexpress seller listing), purchased for SG$4.78 (Dec-2025).

Specifications as provided by the seller:

1. Introduction:

CHA-81 is a LED Follow Spot Lights LED Game DIY Kit. It can make the LED move along the X-axis/Y-axis/XY-axis, and the moving direction can be controlled by the buttons. It can also adjust the speed of the LED movement, resulting in a variety of LED blinking effects.

It is a very interesting DIY electronic product which enables users to understand the circuit more clearly and learn welding skills.

1. Feature:

   1. 81pcs highlight Red LED
   2. Controllable movement direction for X-axis/Y-axis/XY-axis
   3. Controllable movement speed for X-axis/Y-axis
   4. Simulate LED light game tracking effect
   5. Perfect simple circuit
   6. DIY hand soldering

2. Parameter:

   1. Product Name: CHA-81 LED Follow Spot Lights LED Game DIY Kit
   2. Product Number: CHA-81
   3. Work Voltage: DC 4.5V-9.0V
   4. Power Type: 3.5mm Power Socket
   5. Color: Red LED
   6. Size(Installed): 97x73x24mm

Kit Parts

Circuit Design

I haven’t re-drawn the circuit, but I did verify that the following schematic from ICStation appears to be correct for the board.

How does it work? The essence:

• The two 555 timers (U1, U3) are configured as astable oscillators
  • the associated variable resistor (VR1/VR2) adjusts the frequency
  • the associated push-button (S2/S3) selects the timing capacitor
  • Resulting frequency ranges:
    • 6.9 Hz - 144 Hz
    • 31 Hz - 655 Hz
• The timers provide the clock for their associated CD4017 counter
• CD4017 U2 outputs sequentially enable the LED “rows” with a high-side NPN
  • NB: because the overall current is limited by the 220Ω resistor in the LED column, there is no resistor required on the NPN base
• CD4017 U4 outputs sequentially enable the LED “columns” with a low-side NPN
• At any given moment, the LED that is on ON is the one at the intersection of the enabled U2 and U4 outputs
• Pushbutton S4 changes how U4 is clocked. It switches between:
  • 555 timer U3 output
    • i.e. row and column speed are independently controlled
  • CD4017 U2 reset
    • i.e. raster mode. CD4017 U4 increments every time CD4017 U2 rolls-over

Build

Soldering was a pleasurable couple of hours.

The kit was packed with an extra S9015 and a handful of extra LEDs, but these weren’t needed as everything worked as expected.

Credits and References

• “CHA-81 DC5-9V LED Tracking Light DIY Parts Electronic Production Kit 9X9 Dot Matrix Display” (aliexpress seller listing)
  • Originally purchased for SG$4.78 (Dec-2025)
• ICStation - possibly the original kit source
• Component information:
  • CD4017 datasheet
  • NE555 datasheet
  • S9014 datasheet

Julian Ilett’s Investigation of the Kit

Led Matrix Soldering Kit (YouTube)

What it Does - LED Matrix DIY Soldering Kit CHA-81 (YouTube)