Designing a physical parts layout from a schematic - Page 1
Forum section: electronics / beginners

author: Chris Wilson
author_rank: Super Contributor
timestamp: November 25, 2014, 03:10:14 pm
content: I have normally built projects that have a PCB design available for them, or ones so simple a layout on tag or strip board is easy to work out and achieve. I am now about to tackle something that to me is quite a bit more complex. I have Googled for tips on layout design from a schematic and found little, nor have I found any YouTube videos. Has anyone any links or tips on going from a schematic to a layout and how to decide if making a PCB is necessary or if alternative options would be easier yet reasonably aesthetically acceptable? the circuit is in the link, maybe with luck also attachedI intend to have the power supply section on a separate board, and appreciate the MOSFETS may need short leaded components associated with them. I doubt I have time or patience to learn PCB layout software, and asking someone else to do it for a fee may be impractical without them having some of the actually components to hand for sizing purposes. I want to socket the DIP packages. Thanks. Maybe a good video subject for someone to consider making?http://www.chriswilson.tv/136bigtxv2.doc

author: richard.cs
author_rank: Super Contributor
timestamp: November 25, 2014, 04:56:03 pm
content: Some tips for that circuit:1) Print out a copy of the schematic and draw boxes to divide it up into sections. I suggest PSU, high-power RF, small signal TX, small signal RX.2) Think about what bits will get hot and require heatsinking. Highlight these and think about placing them near the edge of the board or by cutouts depending on what you want to do.3) Think about the traces where high currents flow with fast rise times, highlight these and when laying out these are the ones that need to be kept short4) Highlight any sensative RX nodes and put these as far from the high power transmit bits as you can.Hopefully you've now divided the schematic into regions, you can some idea what bits need to be kept scrunched up together to perform well, which bits need to stay away from where. You can then think about placement, whether designing a PCB or doing it with stripboard or even deadbug.

author: Dave Turner
author_rank: Frequent Contributor
timestamp: November 25, 2014, 05:34:41 pm
content: Have a look at Dave's tutorial.I think this is still validhttp://alternatezone.com/electronics/files/PCBDesignTutorialRevA.pdf

author: Zero999
author_rank: Super Contributor
timestamp: November 25, 2014, 07:17:17 pm
content: Please don't take this the wrong way, remember this is the beginner's section. I think you should think twice about building this. The fact you need to ask such questions indicates a lack of understanding of the potential safety issues with this project.Another thing to consider is the legal implications: do you have a licence to broadcast at this frequency?

author: Neilm
author_rank: Super Contributor
timestamp: November 25, 2014, 07:32:57 pm
content: Quote from: Hero999 on November 25, 2014, 07:17:17 pmseconded - the mains will require safety clearance and creepages for starters.

author: lapm
author_rank: Frequent Contributor
timestamp: November 26, 2014, 12:17:25 am
content: I usually recomend external power pack/wallwart for people not experieced with electronics design... Easier and keeps that lethal mains out of your circuit usually..

author: Chris Wilson
author_rank: Super Contributor
timestamp: November 26, 2014, 11:21:17 am
content: OK, thanks for the warnings, no worries about that, I appreciate the concern. I appreciate the potential the mains voltage has, and the rectified 100V plus DC. I am of an age where a few risks hobbying is about as exciting as life gets save when I am motor racing, and I am getting slower these daysPassing to the next life via a good flash and bang sometimes seems less worrying than lying in an old folk's home, wondering when the money is going to run out for a bowl of cold soup and a few sarcastic comments from the whipper snappers clock watching until going home timeThe link to the pdf from Dave was very useful, thanks for that, and the tips from Richard are also very helpful, thank you!

author: Chris Wilson
author_rank: Super Contributor
timestamp: November 26, 2014, 11:52:09 am
content: Well, I am not *that* old, I just feel it, and needed to address that continuing racing single seaters competitively is perhaps becoming a somewhat unrealistic goal as I limp into my latter yearsI failed to say, yes, I am licensed to transmit up to 1 watt ERP on this frequency, and my lossy antenna system will never achieve 1 watt, even with a kW out of the back of the amplifier. Let's face it, what ham does *not* have a very lossy antenna system at 136kHz(Waits for some US ham to post their equivalent of Rugby Transmitting Station in their back yard)....Thanks for the last reply!

author: m100
author_rank: Regular Contributor
timestamp: November 26, 2014, 12:21:06 pm
content: Quote from: Chris Wilson on November 26, 2014, 11:21:17 amI still recall the noise of a colleague touching 650v DC in a lab 30 years ago. No injuries apart from a few strained stomach muscles from us laughing at his girl like squeals. He was bloody lucky though