I am trying to send PWM, clock, latch and blank signals from Arduino through a series (16) of TLC5940 Breakout boards and on to a grid of 512 individual controlled LEDs six feet away (RJ45). I am using op-amps to help get the serial signals pushed through the large number of boards. Power and Ground are in parallel.
Of course, I am having problems. The set-up, as pictured, works well until the 9th or 10th board, then things get wonky. They are getting power but not individual control -just flickering.
I am trying to troubleshoot. The whole thing is powered by 12 V, 30 A switching power, buck converters for three different voltages (10 V for Arduino, 4.7 V for op-amps, 6V for boards and LEDs).
I am wondering if I should tie all grounds to a single common line back to the power source (V-) or do the individual voltages (10 V, 4.7 V, 6 V) need their own ground line back to power source? Example: the five op-amps – 4.7V+ and 12 V- single line common ground? – or should they have their own ground line all wired back to the 4.7 V converter and its 4.7 V-?
Best Answer
There's nothing inherently wrong with using power line buses. Star wiring might not solve the problem.
Ideally, you'd use an oscilloscope to see how stable the power lines are. But I'll assume you don't have one.
Consider centre-feeding the power lines, rather than feeding the power in at one end. That reduces the cable runs.
Consider using fatter wires. The volt drop in a thin wire could be too high. Digital devices often require sudden spikes of current, so the power lines could be dipping even if the average voltage measured by a voltmeter looks good.
Consider adding capacitors - electrolytic and/or ceramic - between the power lines and ground near each board (you already seem to have a few ceramic ones on some boards only). This could end up a bit trial-and-error. Too little capacitance won't achieve what you want, too much will overload the power supplies on power-up causing them to shut down.