PI CHIP

[sido]

Suggestions? Leave space for a popcorn 3 terminal linear regulator, those are usually pretty quiet in emc contribution. One thing to consider is having low value series resistors (series termination, too) for digital io lines, if driving long jump wires or pin connections.

Great consideration, What value resistor's should be considered? Is this for all I/O connection lines between sub-modules (analogue/digital)?

The analog connector port should have the analog ground and ADC supply voltage connections, to continue those voltages - they're the "analog" ground and supply, and they usually connect right next to ADC to the digital world, otherwise separate to keep the analog vdd/gnd from being a conductor for digital current loops. AVDD should be filtered and separate from the digital VDD, but often needs to be present at the same time as the digital VDD. This is sometimes a make/break case for separate ADC even if the microcontroller's ADC would be "good enough" otherwise.

It's also important to consider the current route into a transient inducing component, the input of a switch reg or transistor can be a route of radiated/conducted noise as well as its output.

How about input power supplied for MCU on-board regulator is isolated totally from further sub modules via its own 2wire shielded power cable and connected to the main power supply module further inline with additional RF bypass capacitors, therefore bypassing in-between sub modules.

We usually want only the intentional search coils in our device

Not sure what you mean here, but i will take a guess that your referring to unintentional component leg(s)/connector's Induction loops created due to the inevitable longer sub module Interface Header connections with such proposed outlined design??

Thanks for the effort for everyone involved - there are often lots of people with suggestions but few people actually spending the sweat with the pcb program and workbench! If these tips saved a few more minutes of debugging than it took to read them, then it was successful...

I am no circuit designer by trade. Just a regular common Tech to be understood, but willing to learn though and your suggestions are a real benefit and most welcomed. Keep suggestions forthcoming as the main PCB design evolves.

BTW, i just started to learn a PCB layout program ( Diptace-----thanks Mechanic), which with upon further reading in low frequency circuit designs, will aid me in employing new experimental designs with critical PCB layout principles as such.

Cheers Sid

[ODM]

Suggestions? Leave space for a popcorn 3 terminal linear regulator, those are usually pretty quiet in emc contribution. One thing to consider is having low value series resistors (series termination, too) for digital io lines, if driving long jump wires or pin connections.

The analog connector port should have the analog ground and ADC supply voltage connections, to continue those voltages - they're the "analog" ground and supply, and they usually connect right next to ADC to the digital world, otherwise separate to keep the analog vdd/gnd from being a conductor for digital current loops. AVDD should be filtered and separate from the digital VDD, but often needs to be present at the same time as the digital VDD. This is sometimes a make/break case for separate ADC even if the microcontroller's ADC would be "good enough" otherwise.

It's also important to consider the current route into a transient inducing component, the input of a switch reg or transistor can be a route of radiated/conducted noise as well as its output.

And finally all signal connector pins in/out the board should have an according gnd pin close to them, hopefully all "unused" pins, to make the smallest possible current loop area. Especially for digital signals which usually emit interference, and analog signals which can be sensitive to receive interference. We usually want only the intentional search coils in our device

Thanks for the effort for everyone involved - there are often lots of people with suggestions but few people actually spending the sweat with the pcb program and workbench! If these tips saved a few more minutes of debugging than it took to read them, then it was successful...

[sido]

You suggest no mosfets on the main board, but still a non synchronous switching regulator without two-stage filtering? A linear reg option would be nice to leave in, just in case the switcher/layout/inductor proves noisy. I imagine the universal board's layout would have plenty of free space around parts and elsewhere for potential modding - always nice for prototyping.

This is for a basic UNIPI timing device that can be adapted to say Goldscan IV, SurfPI, Tinkerers great design suggestions, SD2000 frontend/backend audio with modified updated circuitry or a new latest low noise frontend device that may become available in future new designs when developed, which can be experimented with such MCU setup. Power supply circuit was for reference to power MCU only and did not consider a synchronous type. Any suggestions? Might as well include it for convenience.

Synchronous noise is far easier to live with when sampling, so a synchronizable switcher option is worth considering if the switcher reg stays - the cpu can provide this. National makes sync capable switch mode regs in their "simple switcher" product family as well.

Thanks for the suggestion. Will look into it. Plenty of free space to include it on MCU PCB.

Yes there will be plenty of free space to experiment with and will be isolated from TX and frontend amps.

That is my idea of going down this path as to minimize unnecessary internal noise, but most important to make it Universal in all aspects as outlined in previous posted pictures.

The coil driver can be rather noisy with fast high current switches, sure, but it's synchronous and thus doesn't usually prove an issue for PI frontends unless it's excessive, usually from poor bypassing or crazy layout.

And yes, mosfet drivers should be located as close to the switched transistor as possible. Those make for pretty high current transient loops.

Isolating the Mosfet drivers and TX frontend stage this way allow further shielding like full shielding in metal or copper PCB eclosures between each sub-modules and maybe the use of feedthrough caps at critical points for minimal internal noise if there is any benefit.

Another reason why i would prefer to isolate the Tx/sampling Mosfet drivers is that some circuit designs in the TX stage may not require them ( PCB component footprints) as other driver designs may be incorporated in different experimental circuits.

Moodz great work offered is universal in schematic/software design but there is no practical layout to assist for experimental use, which may be implemented into a workable in the field detector with additional sub-modules

Thanks for your input. Any more suggestions are welcomed.

Cheers Sid

[ODM]

You suggest no mosfets on the main board, but still a non synchronous switching regulator without two-stage filtering? A linear reg option would be nice to leave in, just in case the switcher/layout/inductor proves noisy. I imagine the universal board's layout would have plenty of free space around parts and elsewhere for potential modding - always nice for prototyping.

Synchronous noise is far easier to live with when sampling, so a synchronizable switcher option is worth considering if the switcher reg stays - the cpu can provide this. National makes sync capable switch mode regs in their "simple switcher" product family as well.

The coil driver can be rather noisy with fast high current switches, sure, but it's synchronous and thus doesn't usually prove an issue for PI frontends unless it's excessive, usually from poor bypassing or crazy layout.

And yes, mosfet drivers should be located as close to the switched transistor as possible. Those make for pretty high current transient loops.

[sido]

Put this on-board power supply Regulator circuit also with 2 male pin headers for input voltage. Dont include the 8 Mosfet switching drivers. So its MCU, crystal, caps, power supply, Toggle and pin header connectors etc.

Also include the ICSP connector somewhere near the edge of the board. I believe you are able to get 90 Degree Connectors to suit.

See below circuit.

Cheers Sid

[sido]

awww shucks.

Moodz, i hope you are not regretting it now

We are 1/4 of the way there, hehehehe, only jooookiiiinggggg.

Cheers and thanks
Sid

[moodz]

awww shucks.

[sido]

Sorry, sido, still haven't got up to do anything. (I'm a crappy designer, huh?) We've been house-hunting today, and we found one. So that's gonna mess up the next few weeks. But meanwhile, I should still be able to do design and layout stuff. I've installed Protel on my laptop, which runs about as fast as a 486 doing rendering, but it *does* run. So I'm going to get started tonight. I've got the footprints and schematic components imported, and from the photos it's clear that your rotary switch is a simple 3-pin 0.1" pin pitch around a .500" (500 mil) square. I've added additional pads and padded out the footprint, it will work well. That's it for now. I'll post an update later tonight.
Cheers,
Pete

Oh, yeah, I was so excited to see Paul's go-ahead, I forgot to say Thank you, moodz, you're a champion of the poor, downtrodden tinkerers! You made my day with that thumbs up, and I know sido had a smile too. Thanks, mate. Much appreciated. Now I have to really do something instead of tout my skillz!! (You utter, utter, utter, utter... )

Thanks Pete, that will be great, much appreciated

Please do not include Mosfet switching transistors on this main MCU board as this could introduce RF interference due to no shielding and close proximity to the LCD Module, Just add pins to the MCU board for the Mosfet switching which will be located on the next future board to be designed and added with Hex Spacers........which will have the mosfet switching and TX combined so as to be shielded with PCB groundplane which is located away from the main MCU and LCD Module. I will post some more info as to where the I/O pins of the Mosfet switching devices should be located later tonight. I say on the top of the LCD Module protuding behind MCU board. Design it with 2.54mm spacing for the required pin count to use straight male header connectors.

Use only single line male headers where needed for sub board connection. You can actually buy the the female headers from Element14 (stock number 488-1724) to suit the LCD Module interface to MCU PCB. They are 2.54mm spaced also. So the only connectors used for interfacing PCB's are male/female single line PCB headers or PCB jumpers (stock number 334-561). The male header connectors stocked at Element14 are (stock number 251-8351).

Not sure about Power Supply. Should we have a on board 5V PS on MCU?? for ease of removing MCU so as to be dependant on its own for other projects.??

Dont know if you read my post on PCB design software, but i have decided to learn PCB design using Diptrace. I still have a long way to be able to produce quality boards for now, so this PI controller PCB, the heart of PI will assist me later to design further sub modules as to this layout, that you are greatfully assisting which is much appreciated.

Yea, Kudos to Moodz approval

Cheers Sid

[Pete the Builder]

Sorry, sido, still haven't got up to do anything. (I'm a crappy designer, huh?) We've been house-hunting today, and we found one. So that's gonna mess up the next few weeks. But meanwhile, I should still be able to do design and layout stuff. I've installed Protel on my laptop, which runs about as fast as a 486 doing rendering, but it *does* run. So I'm going to get started tonight. I've got the footprints and schematic components imported, and from the photos it's clear that your rotary switch is a simple 3-pin 0.1" pin pitch around a .500" (500 mil) square. I've added additional pads and padded out the footprint, it will work well. That's it for now. I'll post an update later tonight.
Cheers,
Pete

Oh, yeah, I was so excited to see Paul's go-ahead, I forgot to say Thank you, moodz, you're a champion of the poor, downtrodden tinkerers! You made my day with that thumbs up, and I know sido had a smile too. Thanks, mate. Much appreciated. Now I have to really do something instead of tout my skillz!! (You utter, utter, utter, utter... )

[sido]

Hi Moodz, thanks for the thumbs up

Cheers Sid

[moodz]

Hi Moodz, thanks. Is that a YESto pursue the design of your MCU Controller on a generic PCB layout on open Forum??

Well, a little bit more information added below.
The reason why we should follow this path is shown below in Pictures.

What do you all think?? Any suggestions?? At this stage its only MCU PCB, Switch PCB and LCD Module.

Cheers Sid

[ATTACH]23278[/ATTACH][ATTACH]23279[/ATTACH][ATTACH]23280[/ATTACH]

YES

[sido]

Hi Moodz, thanks. Is that a YESto pursue the design of your MCU Controller on a generic PCB layout on open Forum??

Well, a little bit more information added below.
The reason why we should follow this path is shown below in Pictures.

What do you all think?? Any suggestions?? At this stage its only MCU PCB, Switch PCB and LCD Module.

Cheers Sid

[moodz]

Hi Pete, someone on this forum had the same idea for another project, but doing me head in trying to locate the picture.

"If you're happy with 200mil screw-in battery connectors (green, orange, or blue connectors like they use in burglar alarms and so on), that kind of more-or-less standard stuff, then that'll be quicker, but again, if you have a particular preference and can point me to a footprint, I'm always happy to improve my library!"

I think i know which ones you mean. will post a pic also soon.

I am gathering now some parts at my disposal and knock up the idea of layout. Similar to my famous drawing.
Those switches from Jaycar are ok. I have some around here.

The Toggle switch link posted by Moodz to you is the one i would be using also. Datasheet is supplied with mounting footprints. Can be bought from Element14 at $1.40 each. I have similar toggle switches here removed from a Clarion Head unit. Love recycling parts.

Give me couple of hours and will post the picture with parts i have at hand which are univerally used and easy to obatin.

Oh and Moodz, if your reading this, please let us know if we can proceed with your approval or not???

Cheers Sid

good job ... Keep going .... One of my posts seems to have disappeared??

[sido]

Hi Pete, i made up this basic board layout.

The toggle switch and press switches is from a disected Clarion for illistration purposes. Seperate board on its own.
LCD Module can easily be removed and the switch PCB to reveal beneath on the main PCB the Microcontroller and Mosfet switching.

Just got to work out what connectors to use for Plug in LCD Module and Switch PCB interface connector to main PCB and where to place I/O pins for convenience to be able to connect to sub Modules off this design.

I will keep brainstorming and add more info with everyday actual parts.

Cheers Sid

[sido]

Hi Pete, someone on this forum had the same idea for another project, but doing me head in trying to locate the picture.

"If you're happy with 200mil screw-in battery connectors (green, orange, or blue connectors like they use in burglar alarms and so on), that kind of more-or-less standard stuff, then that'll be quicker, but again, if you have a particular preference and can point me to a footprint, I'm always happy to improve my library!"

I think i know which ones you mean. will post a pic also soon.

I am gathering now some parts at my disposal and knock up the idea of layout. Similar to my famous drawing.
Those switches from Jaycar are ok. I have some around here.

The Toggle switch link posted by Moodz to you is the one i would be using also. Datasheet is supplied with mounting footprints. Can be bought from Element14 at $1.40 each. I have similar toggle switches here removed from a Clarion Head unit. Love recycling parts.

Give me couple of hours and will post the picture with parts i have at hand which are univerally used and easy to obatin.

Oh and Moodz, if your reading this, please let us know if we can proceed with your approval or not???

Cheers Sid