The PCBs arrived two weeks ago from the fabhouse. They look great and professional and are of good quality. However I can already spot some design mistakes that I’ve made, and can think of some improvements:
- Some vias are too close to solderpads.
- The Bosch BMP180 appears to be hard to get your hands on, so I am thinking of going with another sensor, like the MPL3115A2, which is widely available.
- I’m thinking of putting the LCD on the back of the PCB, but I like the flush backside I have now.
- Switch to using 1206 smd resistors instead of 2010. I thought it would be easier to solder, but 2010 resistor appear to be hard to get. 1206 are more common.
- Originally I wanted to use a ~2500 mAh LiPo batter, but those too appear to be hard to get, so I’m considering switching to using 18650 lithium batteries, they are easy to get (ebay is full of them) and there are easy PCB mount available. Thus solving the problem I had with mounting the lipo to the pcb.
- Use one pcb layer as ground, this will cut the amount of traces in half, and will need less vias. It will also decrease the ground resistence and increase the current handeling capability, which is a good thing.
- Use the auto router less, the traces look terrible.
So these points will probably be the improvements to v1.1 of the pcb design. I have not tested the PCBs yet, because I’m waiting on some components to arrive.
Today I added some features to the circuit, a latching push button on/off and backlight switch. The on/off button is connected to the enable pin of the LDO. After I finally finished the circuit I started on the board design, which was something I had never done before. But with some help from the autorouter I finished it quite quickly. Then I’ve sent them over to pcbway, who made 10 boards for 20 dollars inc shipping. Now it’s time for the waiting game.
files (sch, brd and gerber (.zip)):
Today I came a long way designing the circuit for the thermometer project. I found out that powering the atmega328p-au directly from the vbat pin of the charge controller wouldn’t give a lot trouble, but other components were a bit more picky. So I opted for a LDO voltage regulator (MIC5219-3.3v), which has a low dropout voltage and even works as a dc-dc upconverter! Sadly the datasheet is not very extensive on example circuits, but I guess the battery voltage is stable enough so support circuity is not really necessary.
I mostly used the Sparkfun eagle libraries and I looked at some breakoutboards from adafruit to see how they hooked things up. It’s released under the Open Hardware and CC Share Alike 4.0 licenses.
Now I’m going to check the circuit a few times, and then I’m off to prototyping on the breadboard and designing the pcb.
Here are the files:
Arduino Thermometer (.PDF)
Arduino Thermometer (.SCH)
After brushing up on my eagle skills, I almost completed the design for the powersupply for the thermometer project. It uses the MCP73831 charge controller, hooked up to the usb connector and to the battery. I’m not shure if I can hook the Vbatt pin of the chargecontroller directly to the atmega’s Vcc pins, but we have to find out I guess.
Yesterday I did a lot of research online on available components and I came up with the following components and functions.
||Temperature and humidity sensor
||Barometric pressure sensor
||Charge management controller
||Generic 16×2 character LCD
||8-bit-AVR-Microcontroller TQFN package
||2500mAh LiPo battery
The thermometer should incorporate the following functions:
- Display absolute temperature in degrees Celsius, at 1 decimal point resolution (maximum resolution according to the datasheet)
- Display absolute relative humidity in percentage, at 1 decimal point resolution (maximum resolution according to the datasheet)
- Display absolute air pressure in hPa (mbar), at 1 decimal point resolution (can do up to 2 according to datasheet, but it’s not necessary and takes up valuable space on the lcd)
- Display battery percentage left, at 0 decimal point resolution (measuring battery voltage with the adc, using onboard 1.1v reference)
- An ability to turn the device on and off with a push button
- An ability to turn back light on and off
- Operate from battery and mains
- An ability to charge with a standard phone charger with micro usb port
- An ability to use a ICSP programmer to upload new sketches
I’ve linked the adafruit breakout boards for most of the components, but in the end product I will just use the chips and support circuity. It’s convient to look at the adafruit pages because all the information is located in one place.
Featured image By Fabian ~ (Fabian R at de.wikipedia) – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=15684889
I have been into electronics for a long time now and always had the desire to built one of my designs on a pcb. And with cheap pcb prototyping services from China that has become very easy and cheap (about 30 usd for 5 boards). I want to make something usefull aswell so I decided to start off with something simple, a thermometer. Much like the one I made on a breadboard a while ago. I do want to use a bigger display though. In order to get this done I have to take the following steps:
- Stating exact functions of the thermometer & choosing components
- Designing the circuit
- Prototyping on breadboard
- Designing the pcb
- Assembling pcb and testing
- Designing an enclosure (3d printed or wood)
The project will be entirely based upon open source hardware. I will try and log my progress as I get along with this project. If the project is succesfull I might sell the remaining boards as a kit, with detailed instructions.
I have been working on a Quadcopter for about a year now, but about half a year ago I lost motivation for the project. Now finally found some motivation to continue with the project. I started it because I really like everything with a remote control and lots of electronics in it xD. Also it was a lot in the news a year ago, with all the NSA and army things (civillian surveillance, remote attacks). The original plan was to make a drone as cheaply as possible, while also having a lot of opencource hardware/software, so no DJI controllers etc.
Rightnow have the following things complete:
- Frame (found it on ebay awhile ago)
- Flight controller (MultiWii PRO 2.0 from readytoflyquads.com)
- Remote Control (Turnigy 9x)
I chose the MultiWii because it is Arduino based, and if you didn’t know, I LOVE arduino. It’s modular and easy to understand, and yet powerfull enough for most tasks. I chose the Turnigy basiclly only because everyone uses it (lots of info) and you can upload your own firmware to it.
That leaves the following things to be bought/ done:
- ESC´s (Speedcontroller for the motors)
- Battery + charger
- Power distribution
The second list lists also the most expensive parts of a quad build, probably about 100 euros (150 dollars). And it is the most work.
In the future I would like to add FPV and GPS location fixing.
Good links for building a quad yourself are:
Normally the lab is this cold harsh place, mostly due to the TL lighting. But today while I was testing my leds for my 4x4x LED cube, I turned the lights down and it looked real cosy with the red lights (on the run)
With the red leds:
Will be updating soon on my ledcube.
I recently came across a bargain on Marktplaats (Dutch Craigslist), a Dell PowerEdge 2950 II with 4* 1TB HDDs. This was a no brainer. Buying the disks alone would cost equally as much. Picked it up a few days ago and the server is running VMware ESXi 5.5. I currently have set up FreeNAS as a VM, it’s running SABnzbd, couchpoatato and sickbeard. I’m planning to make some more VMs to run a VPN and do some backups, but I need to upgrade the CPUs and RAM for that. Right now it only has a dual core xeon x5100 @ 1.8ghz and 5GBs of RAM. The CPUs and RAM are dirtcheap on eBay.
In two weeks the projectweek at my school will start. I was asked to come up with a good assignment for elementary school students, who will soon attend our highschool. The scope of the project had to be technical. The assingment will be: “Make your own Wheater Station”. I went for the Arduino platform, as it does a good job at combining physics and computer science. I will provide all the equipment and a manual, the kids have to build it. Earlier this week I wrote the code, and now I have made the circuit myself. The project consists of a pressure sensor (BMP085) and a combined temperature and humidity sensor (DHT11). The readout will be displayed on a 16*2 character LCD display. I will upload the (dutch) manual and the code soon. Expect an instructables.com link this later this week.