For my engineering class, I am building a digital scale. My team has assembled the prototype out of:

  • Arduino Uno
  • Hx711 amplifier module
  • 1 kg load cell
  • 2 push buttons
  • A 4 digit 7-segment display module we found online, but we don't know its specific name
  • HC-05 Bluetooth module, no specific manufacturer
  • Lilypad switch CR2032 battery module
  • DC-DC step up to 5V boost converter module

Our prototype works. Well, sort of (we're still trying to work out the boost converter and c2032 to work). We have diagrammed how each module connects to each other on a piece of paper. However, we want to properly diagram this in a way so we can create a PCB for it.

I have tried the Eagle and Fritzing programs. I am very inexperienced with them. I am not able to find the HC-05 and LED display .sch or .fzz files online for this, so I have came to a halt. I am not sure how each of these modules are actually wired together either.

What can I do next?

closed as too broad by Chris Stratton, user31481, per1234, jose can u c, gre_gor Nov 29 '17 at 15:29

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • 1
    I'm a bit unclear what your question is. If your prototype works, can you not look at it to find how it's wired together? There are many good tutorials on Eagle. Don't bother with Fritzing - it seems easy at first, but you'll hit its limitations very quickly. – Mark Smith Mar 3 '17 at 16:28
  • Thank you. I'm lost as to what to do next, as no one in my school knows about PCB manufacture. – MN Chino Mar 6 '17 at 14:23
  • As I wrote there ^^, I don't understand what you're asking for help with. Could you clarify please? Removing all information from your question which is not directly relevant to the question would be a good way to start. – Mark Smith Mar 6 '17 at 15:52
  • You're enrolled in engineering at a school where nobody (not even the teachers?) know about PCB design? I found Fritzing to be very useful for new users, you should check out some youtube tutorials on how to import components you find off the web. Also, probably running the whole thing of a CR2032 won't last long with the 4 digit 7 segment display, afaik. Have you calculated the power usage? Engineering isn't just flicking some parts together ;D – Paul Apr 2 '17 at 16:57
  • You can just place a pin header on your diagram, where you'll want to solder (or mount) the HC-05 module. Or check the internet for existing HC-05 fritzing files. For the 4digit7segment I think you'd be able to find a genereic one. Mind the difference between common anode/cathode and you'll be fine. – Paul May 2 '17 at 17:54

You can find the parts on fritzing.org. Anyway. You can get rid of some parts and save money if you pick the right ones. Instead of an Arduino Uno take an Arduino Pro Mini with 3.3V and HC-05 without a breakout for 5V Arduinos.

Doing that everything will smaller and running on 3.3V thus getting rid of the DC-DC converter.

  • Sorry, I am very inexperienced. Would I be able to run everything at 3.3 volts with a CR2032 coin cell battery? That is why I have the DC-DC converter. I am not able to use AAs as I am trying to use as minimal space as possible – MN Chino Mar 6 '17 at 14:31
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    Possibly. But you have to take tight control over everything. I assume your Scale will be off most of the time. If you turn everything off and put the Arduino Pro Mini into sleep you can get as low as 1µA. A coin cell battery like CR2032 has something about 200mAh capacity. So it can stay in sleep mode for 200'000 hours or 22 years. Of course the battery will self-discharge much faster. While active your components will draw much more power. You need to examine how much power all your components draw and if you can turn them off. This can be a long path of trial and error. – Kwasmich Mar 6 '17 at 14:47
  • I am trying to use as minimal space as possible - there are quite a few Arduinos that are much smaller than the Uno, for example an Arduino Micro. – Nick Gammon Oct 30 '17 at 5:13

You can try to implement the circuit without an Arduino board on a breadboard. So you can get more information about what works and what not. From there after making necessary changes (if there is any), you can draw the schematics and create a PCB layout using Orcad, Eagle etc.There are a lot of tutorials out there about PCB designing.

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