Saturday, March 1, 2014

Bluetooth Speakers are Complete

I finished my bluetooth speakers that hook up to some old computer speakers. Streaming music from my phone or computer from anywhere in my home. It is not as loud but I could always incorporate an additional amplifier into the circuit. Before I packaged it up, I had everything completed on a perfboard and ensured everything was working. It was not powering at first but it was because I forgot to Ground the board :-/...after that everything worked great.

I packaged it up in a small project box with a 3.5 mm audio jack and it is powered from a 3.3V wall adapter which supplies plenty of current for this project. The two LED's are status LED's to see when someone is connected. Fun and pretty simple project putting some old speakers to use.

Monday, February 10, 2014

Bluetooth Speaker System

We had some old computer speakers sitting around that we utilize in the living room for our ipod or computer. Since I'm a lazy bum I got sick of standing up and "thumbs downing" songs on Pandora or changing songs when we are at the table or entertaining so I went the route of making those suckers bluetooth where we can stream through our phone or computers from anywhere in out place.

I got the bluetooth module from Sparkfun and it has a lot of great documentation on it in regards to getting started. I bought the RN-52 breakout board for convenience but you could go cheaper just buying the module. The speakers I have are 2 speakers and a subwoofer so I cut the audio jack off to see what wires I had. Turnout I had the left speaker, right speaker and a common ground among them. These speakers are externally powered so the signal is already amplified. In the case you would be using headphones or low powered speakers there would be no need to amplify the signal.

Prototype of Bluetooth Speakers
I intend on packaging everything on a protoboard and in a project box. I'm going to power it from a 3.3v wall adapter and add an audio jack if I ever change speakers in the future I won't have to hardwire anything. Functionality wise it works great!

Wheatstone Bridge Hydrometer

So I was not making the wheatstone bridge for my health. My intent was to build a hydrometer for home brewing. There are multiple ways of doing this but I wanted to play around with the strain gages. The principle being the buoyancy of a ping pong ball bolted at the end of a beam would vary as a function of a fluids density or Specific Gravity which is the typical measurement when home brewing.

This was my crude build and attempt at utilizing it as such but was not overall pleased with the results, fun idea. I had a few other ideas for making a hydrometer but ditched them because of cost and complexity to replace a simple glass tube.

Saturday, January 25, 2014

Wheatstone Bridge with the Arduino

Well...I gave strain gages a shot with the arduino and the INA125 amplifier. When I was designing my circuit I referenced a few other people who tried to apply a wheatstone bridge with an arduino. They were utilizing it as a beam in bending to measure mass ranging from 0 - 500 g. I was trying to apply it in much more sensitive application picking up a force on the beam that was 0 - <1 lb. Most people had difficulty in amplifying the signal because they could not balance the bridge or utilized a quarter or half bridge. I opted to use a full wheatstone bridge but it was difficult to get the resolution I needed for a few reasons. They had some reasonable results with the amount of force they were trying to measure.

  • The arduino can only handle a 5V signal. I was forced to use a 5 v source for my bridge which does not leave a large range of output signal for the forces I am reading.
  • After mounting all the strain gages and wiring, there is some slight variation in the resistances of the bridge which shows up as an amplified signal. I was already forced to limit my output range to a few volts. 
  • The resistance I had set for amplification was very touchy. I had to amplify the signal significantly because I was trying to read very small changes in force. A change of a few ohms on the resistance changed the amplification significantly and the amplifier would become saturated reading the maximum voltage.
  • Wiring of the strain gage makes a BIG difference. I would jiggle and bend my wires and peg the output voltage. I probably could have done better with this but didn't want to invest anymore money.
Full Wheatstone Bridge with the Arduino

I  was able to notice some change but it was not consistent and responsive. It was a fun try but don't think I will invest much more time or money into the project. I might start looking for alternative methods of measuring very small changes in force with a common micro-controller. It was interesting working with the Wheatstone bridge and it was the first time I had used the INA125. 

INA125 wired to bridge and Arduino

I have some ideas so stay tuned for what I come up with next. If anyone has suggestions or experience using the INA125 or wheatstone bridges let me know and I'll give it a shot.

Tuesday, January 7, 2014

123D Circuits

Just saw this from Autodesk. I think its pretty great idea and seems pretty functional from the little I have tried. Anyone else give this a try yet?

Monday, December 30, 2013

LCD 16x2 RGB Display

I got this display for my next project. It will be displaying two variables that are being measured with the Arduino. The RGB display can have various colors by grounding the RGB pins (16,17,18). It is a nice display and I'll have it working dynamically updating every few seconds. The project will also have a calibration button and instructions will be displayed on the LCD screen.

LCD RGB 2x16 Display

Adafruit has a great tutorial on hooking this bad boy up. Again, 17 and 18 are connected to ground to get the different colors on the RGB. That is not covered in the tutorial. Rest of the components for the project get in at the end of the week!

Tuesday, December 24, 2013

7 Segment Display from Adafruit!!

Its been awhile. I have a few projects I am working on now but taking my good ol' time. The one I would like to build using the Raspberry Pi utilizes the 7 segment display from Adafruit. I think they look really well on any project and are really easy to use.

This has the I2C backpack and they have a great tutorial on using them. Only need 4 connections and you'll be up and running. 

+3.3V, GND, SData, SClock
The other project I did has a lot of design work and I am starting to acquire and build the parts, pretty excited and I'll be posting on that in the near future. Uses some strain gages with an Arduino.