Joe's Hobby Electronics
  • Joe's Hobby Electronics
    • Electronics Blog

Shift registers

13/9/2013

0 Comments

 
I've been a bit lax recently and whilst I've got piles of content that I need to complete and upload, pressures of starting a new job are taking their toll. I'm hoping that normal service will be resumed soon.

Anyway, I've uploaded an article (PDF document) that attempts to give the reader a brief introduction to shift registers. Theory is all well and good so there are some simple construction details for a PIC based project that can control up to 255 x seven-segment displays. All the source code and diagrams etc are supplied so the constructor can change the firmware to fit their own requirements.

UPDATE 20th Sept, 2013.... Just uploaded the correct version of the PDF file... sorry about that.
0 Comments

PICs, Shift Registers and lots and lots of display digits

17/4/2013

0 Comments

 
Picture
I’ve been experimenting with using a PIC to control long chains of 7-segment LED displays, and to find an approach that I can use to replace the obsolete TIL311 displays. To that end, I’ve created a tech article that describes a simple way to do this. My prototype was 24 digits long; long enough for most applications I think, but could be extended. It’s all done with a PIC18F25K22 running from its own internal oscillator, accepts data from a serial device at 9600 baud, and supports 0 to 9, and A to F value display. The code is written in AMICUS18 BASIC which is free so you can change the software to suit your own application. All the fully documented source code is supplied as well as a schematic of the circuit.

The picure above shows 24 digits (6 x 4 digit modules). The display modules each contain a 4 x 7 segment Common Cathode display, a DIL resisor pack on the modules right-hand side, and there are 4 n-channel SMT MOSFETS underneath.
The advantage of using modules on breadboards is the vast amount of time, and wire that's saved. You can throw a quick circuit together in no-time if you already have the modules pre-built. It also saves a lot of breadboard space.

0 Comments

Completed... at last...

1/1/2012

0 Comments

 
At last, it’s completed and this new programmer will make my life so much easier when it comes to PIC development.

This has been one of those projects that in some ways, I wished I’d not started as there seemed no end to it and everything just seemed to go wrong. I blame the fact that I never really had any time to just sit down and do this project from start to finish, but now it’s completed and working, I’m really pleased I stuck with it.

And here it is.
Picture
Ok, a bit of explanation as to what this lovely, beautiful piece of equipment can do.

Inside the case are six PCBs packed with electronics. There’s a PCB that contains a PSU with 5v regulator and an adjustable voltage regulator; set to around 7.3v that drives the LEDs in the push switches. Also on this board is a MAX232 and associated electronics that provide two RS232 interfaces; more on these in a second. There are four almost identical boards; one per output channel that contain a 16-bit shift register, driver chips and relays. The final board contains the PIC and driver logic that runs everything.

Also inside are two Microchip PICKIT programmers (a PICKIT2 and a PICKIT3).

On the front panel there are four 9-way D-Type connections that can be used to connect an ICSP cable to a project under development, or, in the case of this new programmer, up to four projects in development; this will make multi-PIC projects a lot simpler to develop and debug.

You can select which PICKIT is connected to which of the four ports and you can of course only connect each programmer to one port at a time. The unit also has in-built support for RS232 which I use for project debugging. My custom ICSP cable has provision for serial data to be set from the PIC to the outside world and this makes it possible to send any debugging information from the PIC, into my programmer which level shifts from TTL to RS232 and then out to a dumb terminal emulator. I’ve made provision for up to two serial ports and again, you can select which serial port is attached to which input. The serial ports are also available via four, 4mm banana sockets on the front panel for use within other projects.

The upshot of this is that you can connect one port to each PIC project under development, and allocate either of the internal programmers / serial ports on the fly to each port as required without the need to keep unplugging cables all the time.

The advantage of this new unit over my now obsolescent one (which only support up to three outputs and was very clunky), is that I could, in theory, expend the design to support as many output ports as required. It would be a lot of additional effort to increase the number of PICKIT programmers that can be supported. This was going to be a six port unit but I didn’t have a case large enough at the time. But now I’ve got all the hardware sorted out, it wouldn’t be too difficult to build a larger one if required. I’d need to tweak the PIC firmware that controls everything of course, but that’s no real hassle.

Oh yes, the reason I've used a PICKIT2 and a PICKIT3 is simple. I prefer the PICKIT2 as it's much faster than the 3, but the 3 supportes a couple of PICs that I've started to use that the 2 dosn't. I could have used any combination of programmers if desired, or even completly different programmers. It's just I rather like the Microchip ones.
0 Comments

Long bit length shift register chains

25/12/2011

0 Comments

 
I made a promise to myself to finish my PIC programmer over the holidays. This project, like a many of my projects contain a shift register chain, and this one is 64 bits long which isn’t really a lot, but the firmware controlling the project is quite complex and I’ve been having problems debugging everything. One thing that would be really useful is an external display that I could connect to a project and could give me a visual indication of the state of the shift register chain outpus in the project under construction.

So, I took another slight diversion and built a piece of test equipment that can help.

The analyser can connect to the set of control signals that control a shift register chain within a project, and display on several bar-LED displays, the status of the shift register chain being monitored.

The unit has two inputs so it can monitor two shift register chains in parallel, each of up to 56 bits, or by flicking a switch, combine the two displays together to monitor a single chain of up to 112 bits in length. The project is extendable and could be expanded to monitor shift register chains of any number of bits if required.

The unit is a bit of a compromise as I had to use parts and a case I had available, but it does employ fully buffered inputs so presents minimal external load to the project it’s being used to monitor, and has it’s own internal voltage regulator board which will accept a 9v AC/DC input. With all the LED's on, the unit draws just under an amp !!

At some point over the next few days, I’ll create a basic construction article and include the PCB foils and circuit diagrams etc.
Picture
0 Comments

    Author

    A software and hardware engineer who loves retro computers.

    Archives

    June 2020
    May 2020
    April 2020
    March 2020
    September 2019
    January 2019
    April 2018
    May 2016
    April 2016
    March 2016
    February 2016
    January 2016
    May 2015
    April 2015
    March 2015
    January 2015
    December 2014
    September 2014
    August 2014
    April 2014
    March 2014
    January 2014
    October 2013
    September 2013
    August 2013
    July 2013
    June 2013
    April 2013
    March 2013
    January 2013
    September 2012
    June 2012
    May 2012
    April 2012
    February 2012
    January 2012
    December 2011
    November 2011
    October 2011
    September 2011
    August 2011
    July 2011
    June 2011

    Categories

    All
    18f25k20
    18F25K22
    1-wire
    2114
    2764
    74hc595
    74ls595
    86-0325
    8MHz
    Access Speed
    Acorn
    Acorn System 1
    Alarm
    Aluminium Panel
    Amicus
    Amicus18
    Amicus Basic
    Amplifier
    Antex 1107
    Anti-static Mat
    Arduino
    Assembler
    Backlight
    Bargains
    Basic
    Bat
    Batdetector
    Bat Detector
    Bats
    Bench Audio Amplifier
    Bench Light
    Breadboard
    Bubbler
    Buck
    Bug
    "C"
    Cable
    Cable Gauge
    Cable Wire Size
    Capacitors
    Catalogue
    Clive Maxfield
    Clock
    Clocks
    Common Emitter
    Compiled
    Compiler
    Connector
    CPU
    CPU Simulator
    Crownhill
    Custom Computer
    Custom CPU
    Damage
    Develop
    Diode
    Diptrace
    Double-sided
    Double-Sided PCB
    Dry-joint
    Ds1302
    DS1820
    Ds18b20
    Ebay
    EEPROM
    Electronics And Circuits
    Eprom
    Erase
    Etch
    Evaporator
    Failed Capacitor
    Fake
    Fax Paper
    Ferric Chloride
    Fire Hazzard
    Firmware
    Florescent Tube
    Health And Safety
    Hidden Part Numbers
    High-Voltage
    Hv
    Incubator
    INS8154
    Instruction Set
    Inverter
    Kickstarter
    Lcd
    LM2596
    LM386
    Maxim
    Maximum Current Rating
    Mega
    Mit
    MITx 6.002
    MK4
    Molex
    Mosfet
    NE555
    Nixie
    Nixie Clock
    Npn
    OXO
    Oxo Machine
    Pcb
    Pic
    Pic Basic
    Pickit2
    Pickit3
    Pic Programmer
    Pixy
    Poster
    Pre-amp
    Prices
    Programming
    Project Box
    Project Case
    Project Enclosure
    Psu
    Psu Failure
    Qfn
    RAM
    Rapid Electronics
    Raspberry Pi
    Regulated 5v Psu
    Regulator
    Repair
    Review
    SAD (Segment Address Decoder)
    SCC
    SCC MK4
    Seven Segment Display
    Shift Register
    Silient 700
    Slow Progress
    Smoke
    Smps
    Soldering
    Speed
    Speed Test
    Stepper Motor
    Supression
    Swg
    Switch Box
    Tank
    Tantalum Capacitor
    Temperature
    Temperature Sensor
    Texas Instruments
    Thermometer
    Tic Tac Toe
    Tic-tac-toe
    Timer
    Tools
    Traffic Lights
    Transistor
    Usb
    Uv
    Vbe
    Vcb
    Vce
    W65C02
    Wash
    Weller
    Wirecutters
    Wire Cutters
    Wire Strippers
    Wiring
    Wp3eu
    X2 Capacitor
    X Capacitor
    Y Capacitor

    RSS Feed

© Joe Farr, 2011 - 2020 - Email: HobbyElectronics@kcsl.uk.com