The Spark Gap · 26 Nov 2014 · 42m
Hosts Carl and Corey discuss PCB layout tips for hobbyists, focusing on component placement and power plane design. They cover decisions like single-sided vs. double-sided assembly, grouping components by functional blocks, and the critical importance of placing decoupling capacitors near IC pins. The conversation also addresses thermal management, power plane sizing, via current capacity, and the use of positive vs. negative layers in CAD tools.
makers and hobbyists
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Hosts Dave Jones and Chris Gammell answer caller questions on The Amp Hour, covering topics from soldering iron recommendations and PCB grounding issues to career advice for transitioning into electronics engineering. They discuss advanced PCB design resources for high-speed signals and BGA layouts, and provide technical solutions for implementing capacitive touch buttons in KiCad for a custom dry-aging meat fridge project.
Hank Zumbahlen, an application engineer at Analog Devices, discusses the critical importance of grounding, power supply decoupling, and PCB layout in analog design. He explains how digital return currents and high-frequency effects can corrupt sensitive analog signals, emphasizing the need to separate analog and digital grounds and manage impedance. The conversation covers specific technologies like MEMS accelerometers, sigma-delta ADCs, and digital isolators, highlighting how integration and physical layout impact performance. Zumbahlen also shares anecdotes about testing high-power regulators and designing audio DACs, stressing that understanding the underlying physics is essential even with highly integrated chips.
Todd Hubing, president of LearnEMC, explains that grounding myths stem from confusing signal integrity return paths with EMC ground structures, arguing that high-frequency currents follow the path of least impedance and do not cause ground loops on chassis connections. He debunks the rule that decoupling capacitor placement matters on boards with closely spaced power and ground planes, noting that plane capacitance dominates at high frequencies. Hubing also advises against using common mode chokes on unbalanced power inputs, recommending instead that designers focus on minimizing common mode voltage sources to prevent radiated emissions.
Phil King of Weekend Engineering advises host Elecia White on the end-to-end process of designing and fabricating a custom PCB, from schematic capture to assembly. They discuss the trade-offs between professional EDA tools like OrCAD and Altium, free options like EaglePCB and KiCad, and vendor-specific tools like DigiKey's SchemeIt and ExpressPCB. The conversation covers the critical importance of net lists, PCB layout challenges such as trace spacing and via types, and the logistical complexities of sourcing components and managing fabrication costs.
Hosts Dave Jones and Chris Gammell discuss the challenges of PCB layout, specifically the transition between Imperial and metric units in CAD software, and the iterative nature of schematic design involving component substitution. They analyze the Raspberry Pi's massive commercial success through Farnell and the ethical implications of established companies like Crystal Fonts using Kickstarter for publicity rather than funding. The conversation also covers the history of PCB design tools, patent trolling by Intellectual Ventures, and the hosts' personal projects including a new mill and homebrew RF circuits.
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