Vasile, The solenoid and motor signals are being generated in the box, but will=20 have it's own cable branch. So I'm more concerned about those signals=20 inside the box inducing noise on the low-level serial signals inside the=20 box. I'm still learning about ferrites to select something appropriate to=20 isolate noise inside the box. Cheers, -Neil. On 8/27/2015 2:11 AM, embedded systems wrote: > This is the major problem (the cables) when use a single connector for > power, analog and digital signals. > The power cables and digital wires are aggressors for the analog signals > carried by wires, even if using shielded cables. > > So in such system (but not only) the major concern is to reject the noise > induced in the analog paths by the digital and power signals, the last > being the most aggressive. > As long a bunch of cables will go from the same connector to your externa= l > devices, is likely you'll have plenty noise induced by solenoids or motor= s. > > Once you can separate the cable groups, the noise may be (not *is* for > sure) smaller. Every group of cable should have it's own local ground, bu= t > finally you'll have just one ground. The trick is to avoid the passing of > the noise from one ground to the other as well from one power supply to t= he > other. > > Vasile > > On Thu, Aug 27, 2015 at 4:15 AM, wrote: > >> Hi Neil - >> >> I'd be more concerned with the bundling of the cable - do the different >> wires bundle together in a single cable? Do they go to one destination? = How >> long is it? Any shielding? Is this a ribbon/IDC connector or >> individual/crimped? Is there another ground path (chassis)? >> >> Also, how much resolution do you expect from your analog signals (I assu= me >> you will digitize). What is the source impedance? Amplitude? How many? >> >> I personally would associate any spare ground with the analog signals. >> >> Good luck! >> Stephen >> >> >> >> -----Original Message----- >> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf >> Of Neil >> Sent: Wednesday, 26 August 2015 4:55 AM >> To: Microcontroller discussion list - Public. >> Subject: [EE] Best practices for reducing noise >> >> I'm trying to figure out how best to allocate connector pins for a >> mixed-signal board. The system has high-current, high-voltage, >> repeated-switching signals (motors and solenoids), serial data signal >> pairs, and a number of analog sensor signals coming in. The catch is th= at >> this board has only one 30-pin connector (3 rows of 10 pins each). >> >> Currently, I have, in order starting from one end towards the other: >> - Motor + and - (12V, 6A max) >> - Solenoids (up to 4A, but with reverse spikes will see 30V+) >> - Power & ground (12V) >> - Serial signals (3 pairs) >> - Digital I/O >> - Analog sensor signals >> >> The PCB has the motor and solenoid drivers on one side of the board, pow= er >> supply in the middle (but off towards the back), and 2 PICs that handle = all >> the logic near the other side. The analog circuitry is kept really shor= t >> and off in one corner of the board nearest the end of the connector with >> those signals. >> >> So what I'm wondering is: >> - Is there a better way to organize the signals on the connector? >> - I have one spare pin -- should I run a separate logic ground? >> - If so, where would I connect these on the board (or wouldn't this caus= e >> a ground loop)? >> - If I do or don't, should I split the ground plane so the logic side is >> separate from the motor/solenoid side? >> - Anything else I should do? >> >> Cheers, >> -Neil. >> >> -- >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> >> -- >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .