The most common method is of constructing embedded controller systems is a Printed Circuit Board (PCB). I think all electronics know, that simple PCB is constructed of insulating material like epoxy impregnated glass cloth with a thin copper sheet(s) on one or both sides.

There are many conflicts about requirements on how to design interconnection patterns of PCB. But the main purpose for all is to make PCB reliable, effective and producible. If circuit operates in low speed, then requirements are not as strict as for high frequency devices where parasitic effect cannot be ignored. Each PCB stray has its own resistance, capacitance and inductance. These are main effect that distort the signals.

Ground and Power planes

This is not very actual for hobbyists as they usually develop single or double side boards. But if design uses four layer board, then it is recommended to dedicate two layers for power and ground. So two PCB plains in parallel form a parasitic power supply decoupling capacitance which reduces power supply noise. And of course these plains act as a shield for electromagnetic radiation.

Many circuit problems can be caused of improperly implemented ground. It may cause from noise or erroneous operations to safety problems. Fro instance, because of excessive inductance there can “ground loops” appear. Or maybe because of bad insulation between different grounds like earth, analog, digital the circuit wouldn’t work. Even wrong grounding path may induce a voltage for another circuit. The solutions to these problems may vary. Sometimes it is enough to reduce current flow by using single point ground and shielding.

EMC

Electromagnetic Compatibility (EMC) problem arrise when there are a big number of electronic devices used witch radiate electromagnetic energy at frequencies close to communication frequencies. To solve EMC problem first you need to identify it, then you need to eliminate or reduce it to defined limits by using shielding or simply removing/replacing noise signal source.

ESD

Electrostatic Discharge (ESD) is also important consideration in embedded systems. ESD also have potential for failures and errors in operation. ESD usually occur if there is an external electric fields near by. Then the impressed voltages may reach tens of thousands Volts. This simply can happen if you just walk in humidity environment before touching the device and damaging it. The cure is only one- using grounding and shielding.

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This entry was posted on Wednesday, January 17th, 2007 at 1:12 pm and is filed under Electronics. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.