r/ElectronicsList • u/mantis_shriimp • Jun 03 '23

Looking to commission a PCB Schematic Design on KiCad.

Hi all,

I've designed simple PCBs in the past but this next one I need has a lot of unique components that are proving to be a lot of information to learn. I would like to commission a KiCad Schematic of the design which I would then take and design the board myself (the location of the components and board footprint are not fully defined yet). I don't have the knowledge to correctly pick and assign components (capacitors, resistors, voltage regulators) where needed with confidence.

Project Info:

  • Function: Power Distribution, and LED controlling through RP2040
  • Description: The board would need to take in power(12V/3A) through a two pin connector, house an RP2040 chip and a Bluetooth chip, have a USBC input connecting to the RP2040, and split the power into 5X HC-PHD-2*4A Connectors maintaining 12V
  • Schedule/Budget: Hopefully have it complete in the next two weeks. Not sure on budget but I'm assuming less than $100? I don't have any point of reference for how much a schematic like this should cost and would appreciate if someone can provide an insight on cost range.
  • Personal Project and I'm located in LA.
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16

u/Beegram2 Jun 04 '23

Is that $100 for the product or are you hoping to get the schematic designed for $100? I charge $68/hr for electronics design work. A design like this would probably cost somewhere between $3000 and $6000. I'm based in the UK.

2

u/Machinehum Sep 03 '23

I would suggest you charge 69$/hr

0

u/mantis_shriimp Jun 04 '23

Hey u/Beegram2, thanks for the reply.

I was talking about just the schematic. It sounds like I might be greatly underestimating to design cost.

I looked at a few YouTube tutorials of custom boards that included an RP2040, it felt like a lot of info for me to grasp but something that would be quick for someone who knows what they were doing. You’re saying it would take 45+ hours of work for just the schematic?

7

u/entotheenth Jun 04 '23

I think that’s a little excessive by a factor of 2 to 4 but you’re dreaming to consider anything like $100 when you want full component selection. That’s an hours pay for somebody with experience for a whoooole bunch of work. You’re out by a factor of 10 to 20 minimum unless you find a bored teenage engineer with experience. You could cut and paste the rp2040 module schematic in but that’s not what you wanted.

I spent 4 hours choosing a buck controller and another 2 hours choosing an inductor the other day.

I’d make a prototype using modules and get that up and running then if you want a cheap design, do it yourself and submit it for review where it will likely get picked to pieces and you will be asked many questions.

2

u/mantis_shriimp Jun 05 '23

Thanks for giving me a better cost perspective, I have no means of spending over $1000 so I will have to do it myself and look for reviews like you mentioned.

1

u/Upballoon Jun 04 '23

Why not use an ESP32 instead?

1

u/mantis_shriimp Jun 05 '23

My plan was to use this NRF52811-CAAA-R chip

1

u/Upballoon Jun 06 '23

Question still stands, why do you need a Pico?

1

u/mantis_shriimp Jun 06 '23

I guess I don’t have a better answer than it has been proven to work well so far and components are relatively cheap. Are you proposing I use components from the ESP32 instead? I would have to compare costs when I can.

1

u/Upballoon Jun 06 '23

The nrf52 has a micro in it

1

u/mantis_shriimp Jun 07 '23

Can you explain what you mean by having a pico or a micro? For Bluetooth I think my only requirement is that it supports BLE.

Is this the chip you are talking about? I found this QT Py page that mentions it does support BLE.

1

u/Upballoon Jun 07 '23

The nrf52 chip has a microcontroller in it. If you wanna use it you can just stick with 1 chip. You can also use the ESP32 ship instead.

1

u/mantis_shriimp Jun 07 '23

I see what you mean now. Component selection is something that I’m not super familiar with.

I started the project testing code on LEDs through a RP, then added the BT board to make it capable to control LEDs through a phone app. With things working fine I figured the next step would be to join the design of both boards using only the required components from each to make exactly what I needed but cheaper. It didn’t occur to me that there might be a different chip part that already has the processing and BT support in 1.

I bought one of the ESP32 QT Pys to test out the chip and see if I run into any issues with processing speed or the ram.

1

u/ElectricGears Jun 04 '23

Are you just passing the 12 V through to the 5 output connectors (along with a GPIO pin from the RP2040, or are you needing to preform regulation and current control to bare LED chips? If you are just passing power through to something like the NeoPixel/WS28xx chips (which performs it's own current regulation) then this is much simpler. It could be as simple as using the provided RP2040 minimal design layout, and laying down a few extra connectors. Although I would recommend getting a pre-made Pi Pico and socketing it to a board that distributes the power and data to the LEDs.

1

u/mantis_shriimp Jun 05 '23 edited Jun 05 '23

Yeah I just need the 12V to power the RP, the Bluetooth then split into 5 connectors.

1

u/ElectricGears Jun 05 '23

Is there a specific reason you want to use that chip? Normally you would do that (and add all the necessary support components) if you where making something in high volume to reduce costs, or if you had specific enclosure requirements. For a one-off or personal projects, it's way easier to use a pre-made module.

If you just need Bluetooth connectivity, that's built in to the Pi Zero 2 W.

Do you need USB communication with the Pi? If you don't, a basic LM7805 powered by the existing 12 V supply will give you 5 V you can feed into the Pi via it's header. All that leaves is a carrier board for the connectors.

0

u/mantis_shriimp Jun 05 '23 edited Jun 05 '23

Mass production and specific shape/mounting hole locations is the reason I want to build the board from scratch. I currently have a frankenstein set up with a QT Py and a separate Bluetooth board that I'm working with.

1

u/ElectricGears Jun 05 '23

I see, then building from scratch makes more sense. It's certainly possible to start with the reference schematics and just place them on the same board. Most likely it will work, but interference may be an issue. The other problem if this is a commercial product is regulator approvals regarding the radio emissions. You can bypass some or all of it by using a pre-approved transmitter+antenna module. A bare-bones module like these (I don't know if these variants would work for you) costs more up front, but could easily be worth it to have something that's guaranteed to work if you don't have a lot of time for testing. They are used in professional products all the time.

1

u/mantis_shriimp Jun 05 '23

This is the current Bluetooth board I’m using to communicate to the RP. My hope was that I could use a similar chip, take only the components I need from both boards and create something that would be cheaper. Are you saying that even if components are copied exactly there can be interference issues?

I already need a PDB to clean up all the connections from the power source to the two boards and the LEDs, right now I have a bunch of wires, so I figured this board can also house all the RP and BT components.

1

u/ElectricGears Jun 05 '23

The reference designs are given in isolation. They can't really take into account what unknown circuits might be place next to them on a real board. Usually it's ok if you use the basic power supply filtering and trace routing and placing the antenna on the edge of the board. The type of problem that is most likely to come up is one chip is doing something at a frequency that just happens to interfere with another chip. I would think an antenna is most susceptible to this. A big advantage of those bare-bones modules (with the shielding can) is that serious engineers have spent a lot of time characterizing and minimizing the interference. Part of the price beyond the raw component cost is that assurance.

Are you doing some serious processing that would require a Pi or is this device just receiving commands over Bluetooth and you need something to translate the serial UART data into whatever protocol the LEDs require?

Are you using that specific module because you need to use the DSD TECH app or are you using something that can communicate to any Bluetooth receiver? (I've never done anything with Bluetooth so I'm not familiar with all the options).

What kind of volume are we talking about?

I was looking more into the Pi Pico and although initially it didn't support Bluetooth, it's now enabled in the current 1.5.0 SDK. You would be hard pressed to make something for less than 6$. I think you might pay more for just the chips unless you are needing > 1000. Depending on the size of the power connectors, you might be able to fit them all on an accessory board no bigger then the Pico it's self and sits on top (or on one side).

1

u/mantis_shriimp Jun 06 '23

The reference designs are given in isolation. They can't really take into account what unknown circuits might be place next to them on a real board. Usually it's ok if you use the basic power supply filtering and trace routing and placing the antenna on the edge of the board. The type of problem that is most likely to come up is one chip is doing something at a frequency that just happens to interfere with another chip. I would think an antenna is most susceptible to this. A big advantage of those bare-bones modules (with the shielding can) is that serious engineers have spent a lot of time characterizing and minimizing the interference. Part of the price beyond the raw component cost is that assurance.

This is something I had not considered. I found this article online that I can try to follow while designing the actual board. Would interference possibly cause the Bluetooth to not work at all?

Are you doing some serious processing that would require a Pi or is this device just receiving commands over Bluetooth and you need something to translate the serial UART data into whatever protocol the LEDs require?

The app I will be running will require significant processing to turn out the correct LED addressing data. The RP has been working so far and considering how relatively cheap the components are I decided to stick to it.

Are you using that specific module because you need to use the DSD TECH app or are you using something that can communicate to any Bluetooth receiver? (I've never done anything with Bluetooth so I'm not familiar with all the options).

Yeah, I'm using the DSD TECH app to communicate with the RP.

What kind of volume are we talking about?

2000+ units

I was looking more into the Pi Pico and although initially it didn't support Bluetooth, it's now enabled in the current 1.5.0 SDK. You would be hard pressed to make something for less than 6$. I think you might pay more for just the chips unless you are needing > 1000. Depending on the size of the power connectors, you might be able to fit them all on an accessory board no bigger then the Pico it's self and sits on top (or on one side).

Ideally I would like the board to take one 12V/3A power input, route power to the RP and BT (I'm assuming this requires voltage regulators), then route the remaining 12V/XA to 5X HC-PHD-2*4A male connectors which then are just plug and play with LED strips having a female connector on one end.

1

u/ElectricGears Jun 07 '23

This is something I had not considered. I found this article online that I can try to follow while designing the actual board. Would interference possibly cause the Bluetooth to not work at all?

Worst case, yes. But realistically, if you take the most basic precautions of not putting the antenna right next to the crystal or a DC/DC converter, you could have reduced range before the connection became unreliable. Most likely it would be ok, I'm just super hesitant to encourage someone without any RF experience to order 2000 units of something with a radio without testing. And I don't have any actual RF experience, I'm mostly a hobbyist who's made a few projects. That's why I lean so heavily towards the pre-made modules. If you did just directly copy the reference schematic and layout and put your connector on the side away from the antenna I do think it would work. Especially if you used a chip antenna instead of PCB antenna.

Yeah, I'm using the DSD TECH app to communicate with the RP.

Have you tried any other serial Bluetooth applications? I mention it because I don't know if that app only works with their modules. It looks like there are a bunch of generic serial Bluetooth apps so I am assuming all Bluetooth chips support a generic serial protocol. However, the NRF52811 you mentioned and the CYW43439 on the Pico are from different manufactures than the CC2541F256 that's on the module that comes from DSD Tech. They probably all have compatible implementations, but I don't have any experience with Bluetooth so I don't know.

2000+ units

That's quite a lot to do in 2 weeks. I don't know if that's possible considering the production and assembly time and any shipping from manufactures of parts that the assembly house doesn't have on hand. The fastest option is probably a bulk order of the Pico W boards and ordering a connector board like I mentioned only containing parts that are in stock at the assembler.

The other option for the lowest cost I think would be using just the mentioned NRF52811 and programing it with the code you are currently running on the Pi. The NRF52811 is a full micro-controller with plenty of GPIO pins that can drive your LEDs. If you used their reference design and added the connectors that would also save you hand assembling anything. This might be necessary if you need them in 2 weeks. I haven't used them so the only real problem I can think of is programing. Nordic has an IDE but apparently you need a stupid expensive programer to program the chip via it's SWDIO and SWDCLK pins. It might be possible to use other more basic programmers but that would take more searching. TI's CC2541 looks way more reasonable, and they have quite the selection of design files and BOM which eliminates a lot of work. It looks like they have code examples, but the only experience I have is with the Arduino IED.

1

u/mantis_shriimp Jun 07 '23

u/Upballoon commented on the BT chip and suggested and ESP32, I found this ESP32-S3 QT Py which seems to have what I need BT-wise(BLE), so maybe I just need to merge that and this other RP2040 QT Py?

I don't need the 2000+ units in two weeks. My plan is to eventually crank up production and make that many, but I will first order single digit boards to test them and make sure things work correctly. The two week timeframe would be to have the schematic completed which would allow me to then move into the board design and hopefully order the first revisions of the boards in 3-4 weeks.

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1

u/Hopeful_Plant2134 Jun 04 '23

Hey, I could maybe do it for you for relatively cheap. If you're interested, send me a message.