New to electronics, have a basic build

[PfL597]

Hello there! I am new to not only the forum but electronics in general. I have a lot of learning to do as I have been studying Ohm's law as well as figuring out the basic components I need for my build.

I want to weigh something on a small scale, let's say the maximum weight would be 1 pound while the minimum weight would be 3 hundredths of a pound, and then I want to transmit that data over Bluetooth.

So, I know what Load Cell and amplifier I need.

Microcontrollers and Bluetooth chips are my sticking point. With so many out there that do so many things, I would like something that's cost efficient and small, something that still gets the job done.

What type of Microcontroller do I use and what brand would you suggest? The same question for Bluetooth chip.

Any help at all would be much appreciated!

 

[AnalogKid]

If your weighing platform has only one load cell, then the uC needs only one A/D input if it has an internal reference. That narrows the field to just under i gazillion parts. The real question is what are your programming skills?

ak

 

[PfL597]

They are non existent as of now. I am working with someone on this build. He has the programming skills while I am working on the hardware. I imagine that I may need to learn the programming aspect of this also. I am learning as much as I can so I have started with basic electronic knowledge. I have been doing searches for all of this stuff and have just recently narrowed down the types of each component I need. So while I plan on learning what I need to know to understand the entire circuit I am building, I am hoping to get support from people who have done this type of stuff before so that I just don't start buying parts and learning the hard way which ones are unnecessary.

So keeping in mind that I cannot yet program anything, Is there a microcontroller or bluetooth chip you would recommend to start with, or type of each at least? Since the microcontrollers I have seen vary greatly, i think my simple calculations shouldn't need anything too complex or expensive. I was actually starting to look into the Arduino microcontrollers, but then I just saw Atmel tinyAVR micro's that seem like they are better suited to what I am doing. As far as Bluetooth chip I am just guessing in that area.

 

[PfL597]

I guess another question would be, can I take parts from different manufacturers to try to keep cost down and integrate them together? Or do they need to have some sort of compatibility? Or does it all just come down to the code?

 

[brevor]

The real question is what are your programming skills?

They are non existent as of now. I am working with someone on this build. He has the programming skills while I am working on the hardware.

Well then it comes back to what are the programming skills of the person doing the programming. It would not be helpful to you if we suggested a microcontroller your partner didnt know how to program.

 

[PfL597]

Well then it comes back to what are the programming skills of the person doing the programming. It would not be helpful to you if we suggested a microcontroller your partner didnt know how to program.

What ever the code is we will learn how to use it. This really is just the first step in a huge learning process for us both. If we have to learn multiple types of code then so be it. Learning how to build what we want from small electronics, learning the coding process, and then getting into the mobile platform and how to read our data.

 

[brevor]

Well, many people feel Arduino is the easiest to learn. I can't really comment much because I have never used one.

 

[hevans1944]

I bought two Arduno Uno and two XBee modules to test a point-to-point communications application. Upside is there is plenty of support on the web for this. Downside is it won't talk to cell phones or PC Bluetooth transceivers. Make Google your friend and do a search on Xbee versus Bluetooth for lots more information. For your loadcell app, it seems that a Bluetooth link to a smartphone would be your easiest and least expensive approach. You might even consider just buying a Mooshimeter and connecting your load cell and signal conditioning amplifier to it. Before my cell phone died, I purchased a Mooshimeter and linked it to my Galaxy 4. Easy peasy and the resolution is fantastic. No programming required!

 

[PfL597]

Hevans, thank you so much for the reply. I did get a little excited about the Mooshimeter until I saw the cost. This has to be build cheaply thus it looks like we will be coding everything ourselves. The other opinion and info you provided may prove to be very useful though so again I appreciate you taking the time to respond.

 

[hevans1944]

I can see where a kitchen scale that talks to my cellphone would be a hot ticket item at Bed, Bath, & Beyond. For example, I recently purchased this one on sale at a local upscale grocery store for around fifty bux or so. It has all the features I need to measure out portion-controlled servings and experiment with recipes, including a pull-out display so I can place a larger bowl on the scale, tare it to zero, and still be able to read the weight as I add contents to the bowl. Now, if you can make a similar scale that reads out weight just as accurately to a smartphone "kitchen scale app" using a Bluetooth connection, and sells for less than ten bux... I think I would buy one as a backup for the one I have. Might even go as high as twenty bux, but the "sweet spot" for this kind of thing is $10 to $15. See this Google results page.

BTW, there is a huge difference between "build cheaply" and "build inexpensively." I am all in favor of the latter but suggest that you shun the former. If you are going to make just one of your scales, you may be better off purchasing reliable "name brand" parts from an authorized distributor rather than risk failure by using some no-name components with no history of quality-control that you obtain "dirt cheap" from an Internet seller. Sure, you may "get lucky," but if luck fails you then you have wasted considerable time and effort. OTOH, if you anticipate a production run of 100,000 units or so after proving the prototype, then it does pay to shop around and do your own quality-control after selecting a reliable vendor. Be sure to get in writing what reliable and acceptable means to you.

My "gut" feeling is you should be able to make a low-power Bluetooth scale for about thirty to fifty bux in components, including a load cell, signal conditioner, and microprocessor with analog-to-digital converter and Bluetooth interface module. Be prepared to spend a few weeks (or months) getting it all to play together nicely. You may want to consider the Mooshimeter simply as a nice and vital piece of test equipment, instead of as an integral part of the end product.

There is an intimate relationship between hardware and programming that someone on your team must become familiar with. Software simulation only takes you so far. There comes a time when you have to connect the battery and get the correct results. I know of almost no instance where this happens the very first try. It is an iterative process which you will learn as you progress. Main thing is to have fun in learning how to do it. Please come here often and post block diagrams, schematics, and component lists for our comment. There are people here who can help you with the programming too.

Sounds like a very interesting project! If you complete it successfully, you will no longer be new to electronics.