LED/"LASER" Printers - How are +5000 LEDs addressed/controlled?

  • Thread starter Thread starter NTL2009
  • Start date Start date
  • Tags Tags
    Leds
Click For Summary
SUMMARY

This discussion focuses on the addressing and control of over 5000 LEDs in LED printers, particularly at a resolution of 600 x 600 DPI within an 8.5"x11" printing area. The proposed method for controlling these LEDs involves using shift registers, potentially configured in parallel to achieve a clock speed of approximately 711 KHz, which may enhance fault tolerance and cost-effectiveness. Additionally, the conversation touches on the operational mechanics of laser printers, including the use of a rotating mirror for horizontal scanning and common failure modes related to the scanner motor IC. Relevant service manuals and technical resources are also shared for further exploration.

PREREQUISITES
  • Understanding of LED printer technology and operation
  • Familiarity with shift registers and their application in digital circuits
  • Knowledge of clock speed calculations and timing in electronic systems
  • Basic principles of laser printing mechanics
NEXT STEPS
  • Research "Shift Register Applications in LED Control" for practical implementations
  • Explore "Memory Mapped I/O in Microcontrollers" for advanced data handling techniques
  • Investigate "Common Failure Modes in Laser Printers" to understand maintenance and repair
  • Review "FPGA Design for LED Control" to learn about alternative hardware solutions
USEFUL FOR

Engineers, electronics hobbyists, and technicians involved in printer technology, LED control systems, and those interested in the maintenance and repair of laser printers.

NTL2009
Messages
637
Reaction score
393
I recently re-watched this video:



And I wondered, how are +5000 LEDs addressed/controlled? At 600 x600 DPI and an 8.5"x11" printing area, you need ~ 5120 LEDs across and 6600 scans. At 20 ppm, the scans would need to be less than 3 seconds total ( need to allow time for fusing, etc), so ~ 0.45 ms to "load" 5120 LEDs.

I'm thinking shift registers? One long register would be ~ 87 ns per LED, or ~ 11.377 MHz clock? I'm not sure that speed would be practical across that large an area or not, but it's far less than motherboard speeds. Maybe several (16?) in parallel. With 16 (a convenient digital hardware and software number), the shift registers would only need to be 320 deep, so 1.4 us per LED, or ~ 711 KHz clock? That speed may be more fault tolerant and/or cheaper to implement?

Or a different approach? It just seems like shift registers would be the simplest layout for such a small space (1:1 output with the LEDs, no matrix wiring).

-TIA
 
Engineering news on Phys.org
A LED printer would be easy compared to the significantly faster update of a 4k OLED screen.
 
Reply
  • Like
Likes Rive, DaveE, russ_watters and 2 others
Laser printers use a single Laser diode. The horizontal scanning is done with a rotating octagonal (or maybe it hexagonal, don't remember for sure) mirror.

The vertical (length-wise) scanning was just the paper movement thru the printer.

One of the common failure modes in some early, major brand, printers was the IC (chip) that drove the scanner motor. I don't remember the details but the electrical design was rather borderline. I have repaired a few by replaceing the IC in the scanner assembly and adding a few resistors.

The other, less common failure mode, was the bearings wearing out, requiring a motor replacement; but it was more practical to replace the whole scanner assembly.

The service manual for an early (2004) Laser printer is available here:
https://www.printertec.com.br/arquivos_download/1160.pdf
Lots of technical info there!

Have Fun!

Cheers,
Tom
 
There are a lot of potential methods for writing data to HW in a uC.
In general, I don't really see that this is any different than writing to RAM as viewed from the uP buss. Memory mapped I/O is one common method in larger uC systems. It doesn't take long for a special purpose uP or FPGA to fill up 5K of RAM.
 

Thread 'uA709 op amp compensation'

Most likely this can only be answered by an "old timer". I am making measurements on an uA709 op amp (metal can). I would like to calculate the frequency rolloff curves (I can measure them). I assume the compensation is via the miller effect. To do the calculations I would need to know the gain of the transistors and the effective resistance seen at the compensation terminals, not including the values I put there. Anyone know those values?
View full post »

Similar threads

How Do You Program a Sequential LED Light Pattern in MIPS Assembly?
  • · Replies 3 ·
Replies
3
Views
4K
Multi-Cycle Processor Implementation in Verilog?
  • · Replies 1 ·
Replies
1
Views
13K
Satellite internet constellations
  • · Replies 6 ·
Replies
6
Views
4K
Requesting suggestions for languages, libraries, and architectures for parallel (and sometimes non parallel) numerical and scientific computations
  • · Replies 8 ·
Replies
8
Views
4K
Can Evolved State: Dichotomy Capture Your Imagination?
  • · Replies 1 ·
Replies
1
Views
4K
News Patriot Act 2: Summarized by Alex Jones
  • · Replies 10 ·
Replies
10
Views
4K
News Bush Honest & Trustworthy Until How Many Lies?
  • · Replies 65 ·
3
Replies
65
Views
11K