Very new design person here needing some input

Question

I am creating a project that uses a Raspberry Pi Zero W and an ultrasonic distance measuring device (HC-SR04). I have the code done, but now I want to move from the motherboard to a small PCB that will let me hook up the tester quickly.

Here is a layout I pulled from the web that shows the need to split the signal back to ground to 3.3 volts do it doesn't fry the Pi.

So I took a stab a designing my first PCB using Autodesk eagle. It was a struggle, but I think I got it done. Here is a screenshot of the finished board

On one side I have the pins to match the Ultrasonic-module (IN) and one set of pins to go to the PI (OUT). I am using a 1K AND 2K resistor on the advice of another post to split the signal back. Before I send this out to get a PCP bid, can someone with vastly more knowledge than I look it over quickly and make sure this is correct according to the layout above. I am working on a silkscreen layer for the pins on both sides to help with hookup, but right now I just need to know if I am on the right track.

Thanks.

John

genebren · Accepted Answer

John,

Your PCB looks OK. I say this not completely understanding which pins on your 'IN' and 'OUT' are assigned to. Just guessing at this point but the 'OUT' side looks like Ground, Echo, +5v or Trigger and +5v or Trigger (top to bottom). On the 'IN' side it looks like Ground, GPIO24, +5v or GPIO23 and +5v or GPIO23 (again, top to bottom). If these are correct, then I would say that you PCB looks fine.

Good luck,

Gene

thehwcave · Answer

Hi John, just wondering, making a PCB for such a small circuit seems to be a lot of work. I would just use piece of Veroboard (aka stripboard) ...

katghoti · Answer

FYI for anyone reading this post. I found a company ( https://aisler.net/ ) that I was able to upload my Autodesk Eagle file to and they are printing me 3 boards for 4.71 euro ($5.81) with free shipping to the states. I am not affiliated with this company or site, I just found them when I was designing in Fritzing. So now I should get this pcb in 6 - 8 days or so. Again thanks everyone for the help, and I'll let everyone know what they look like when they get here.

mcb1 · Answer

Great find on the pcb company.

The HC-SR04 states it is TTL and runs on 5V.

I presume that you can drive the trigger pin using the 3v3.

The alternative way to convert levels is these little things which can drive 220mA continuous or 880mA pulsed.

https://www.sparkfun.com/products/12009

Sparkfun are just one supplier.

The above is 4 of them on a board, but you can buy the BSS138 devices on their own.

https://cdn.sparkfun.com/datasheets/BreakoutBoards/BSS138.pdf

In your application the LV would be 3v3 and the HV would be 5v.

Mark

BTW finding your way around the site is ....

"Embedded" may not be the best place and you're more likely to get answers in Raspberry Pi (a Pi zero is still a raspbery)

Very new design person here needing some input

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