A friend of mine asked me to design a home automation for him. He wants me to build something that will communicate with his air condition through an IR receiver that it has, and it will act as a programmable timer, to turn it on and off automatically. This circuit will help you understand how to use the built-in I2C communication module of PIC microcontrollers, and also how to use the Maxim DS1307 Real Time Clock chip.
Using a potentiometer, i control the speed of a PC fan, from 350rpm up to it's max speed (1300 rpm). The fan is a 3-wire PC fan. Using the Pulse-Stretching method, i get accurate RPM feedback, twice a second, and display them on an LCD display.
From time to time, i have use many circuits that generates PWM pulses. Most of them will translate a resistor value into duty cycle change. Although that is handy and easy, sometimes a voltage controlled PWM generator is needed. There are of course those micro-controllers that could make almost any kind of PWM signal translation, but i preferred to study and create a circuit without the use of such chips. I tried to keep it as easy as can be, but without this reflecting to the accuracy and integrity of the output pulses.
I just got a 100 Watts submersible aquarium heater from ebay! No, i don't have a fish aquarium in my house, nor any other living creature larger than bacteria or other microorganisms. The reason that i bid on this item is because i will use it for my homemade PCB etch bath!
Hello to pcbheaven's readers once more!!!!!In the following pages i will present you an RFID reader connected to a pic microcontroller.The pic microcontroller is the pic16LF1939 from microchip and the Rfid reader is the MiniProx 5365 from HID global Secure Identity Solutions.Their datasheets are able to be downloaded from here and here.
The pic runs at 16mhz internal clock speed and the oscillation frequency of the Rfid reader is at 125mhz.The communication between the pic and the reader is accomplished through the wiegand protocol.I will provide extra info of how this protocol works on the reference section.
This project is only to give you a new idea. I upload such projects from time to time, because i know that sharing simple solutions and ideas is more useful than sharing a complete and complex project.
The problem that i had, is that i wanted a battery holder that will hold 4 AA batteries in one series. I will use this pack for my door key-code lock project. I need to have 4 batteries inside the door, so space is critical. I cannot have the typical 4-pack battery holder, because it is too thick to fit inside the door. So this is what i've done:
A walk through on making a professional-like panel label for your project.Equipment required are an inkjet printer, a laminator, laminating pouches, scissors, hole punches, adhesive.
I have began working with SMD chips and especially with my favorite QFN package some time ago, and i have already manage to radically reduce the size of my PCB to minimum, thanks to the tiny footprint of those packages. Slowly i began replacing my titanic through-hole parts with SMDs (whenever possible). One problem that arises with QFN PIC packages is that the microcontroller must be programmed after being soldered to the PCB. I know that there are QFN sockets that i can use to make a QFN chip programmer, but they are still very expensive to get, almost $100 each.PIC ICSP Instant SMD Connector with Pogo Pins - [Link]
One of my latest projects i just finished is a hardware thermal printer driver. This project designed/developed for “Delmac Instruments” as a part of my internship. Thermal printers are used in cash and weighting machines for receipt printing.
What the specific hardware does is to receive ASCII characters, escape sequences in UART and convert them in a printable form to send to printer mechanism for printing. Escape sequences are used to send commands to the printer to change character size, line spacing etc.
Thermal Printers don’t use ink as usual printers but they have a head of tiny resistors in a row (about 384) which behave on the paper as dots. Also they use a suitable paper which is thermal sensitive.
By supplying voltage to a single resistor, you heat the resistor and you make the paper burn at the specific point drawing a tiny single dot on the paper. If you supply voltage to a single resistor and you move the paper at the same time by stepping the head motor you will have a tiny width vertical row. This is the basic. (Resistors are refered as elements).
Over the past few years, I’ve built up a few battery packs for myself and for other people. Most of them worked fine – in fact, one of the first packs I built over five years ago is still in service, working fine in a torch in the bottom of my cupboard.
The big problem with soldering to batteries is that you tend to damage the plastic separator, and the cell seals. This – as you might guess – is not a Good Thing™. In some cases, solder can splatter over the cell’s pressure relief vent. There’s a reason the datasheets make a big fuss about the vent – in an overpressure situation, the vent is used to release the excess pressure in the cell. Needless to say, blocking the vent with solder is never a good plan, unless you’re trying to get a Darwin Award, or you happen to enjoy watching your battery pack undergoing rapid, uncontrolled self-disassembly.
In industry, resistance welding is used instead of soldering. Not only are the welded joints smaller than solder blobs, but they cause less damage to the cell. The only problem is the cost of resistance welding equipment. A low-end resistance welding machine can cost upwards of GB 2,000.
The design is based off of the EEVblog design shown on episode #102. The purpose of the device is for when you need a constant load to test things like power supplies, or batteries. No matter what the voltage coming out of the power supply, the constant current dummy load will adjust automatically to provide the same amount of current.DIY Constant Current Dummy Load -- [Link]
I was digging around trying to find some information on an obscure LCD module, and came across this interesting table (compiled partially in Russian) that correlates a lot of older mobile phones with their specific LCDs, LCD controllers, dimensions, serial bus, etc. If you’re looking for cheap LCDs of a specific physical size or resolution, this might be a good starting point since there may still be spare parts floating around out there. If nothing else, it’s just an interesting read looking at how much time and effort went into this thing (presumably a repair shop owner, or something similar). Original Excel Spreadsheet: http://vrtp.ru/index.php?act=Attach&type=post&id=385043, or safer HTML conversion courtesy google.Interesting Mobile Phone LCD Spreadsheet - [Link post]
The projects I do tend to fall in one of two buckets – either proof-of-concept (so I can learn new stuff) or items that have some sort of functional use. The need for this project came about when my wife was prodding me about the humidity in the house and whether our humidifier was doing it’s job correctly. Most people would just go out and buy a temp / humidity sensor and be done with it. However, if you have a look around here, you will see that I don’t fit that mold. Instead, I decided to build an accurate temp / humidity sensor with a Sensiron SHT11 to read the values, a RBBB Arduino kit to process everything and an Adafruit 128×32 OLED to display the results – all wrapped up in… LEGO! Read on for more…
Pinguino32-DIY is now fully functional. The board is working with its own HID boot loader.
We have now some work to do to incorporate this board in the Pinguino IDE. The job should be done this week and we should propose a new version of the IDE next week-end !!
At this moment,’GENERIC250F128′ works with a 8 Mhz crystal for a finally system frequency of 40 Mhz. The goal is to make it work with the internal oscillator.
