The First Project (aka The Gear Indicator)

This unit is designed to display the current gear in bike engined cars. It is based around a PIC 16F84 Microprocessor. These can be programmed using the NOPPP software. Alternatively I can program them, when they'll cost about ten pounds each [e-mail me if you want this option].

When fired up, the unit will display a bar "-" until a neutral signal is received when it goes to "0". The car will normally be in neutral at switch on anyway, so the unit will go straight to "0". This calibrates the unit. From then on the unit should work as planned (as long as the up microswitch is activated on an up-shift etc). If the unit becomes disorientated, and a shift is performed when it should not be possible (eg an up shift whilst in 6th), the unit will display an error image until reset. For an overshift ie it "^", for an undershift it is "V". The unit will reset when switched off. The display may therefore display the following symbols:

Please note.....

  • The LED is a common anode display. All the bits can be bought from Maplin electronics.
  • The PCB tracks are as viewed from the top.... This is so if you use an iron-on etch resist system, the tracks are the right way round after ironing (which reverses the image). If you're drawing them by hand, use a mirror image....

    You will need to decide....

  • Electrical or mechanical reverse mechanism
  • On board 5v regulator or external supply

    With the electrical reverse option, the relay is only operated in neutral. The wiring from the reverse button to the mechanism goes via the relay. In this way, reverse is only available in neutral.

    With the mechanical reverse mechanism, the relay is operated in neutral or first. The relay is used to activate a small solenoid. This pulls a small pin out of the way, allowing the reverse box lever to be moved. This stops the reverse box being used at speed.

    Most people will want to use the on-board 5v regulator. However, if you've got a regulated 5v supply from a seperate circuit you can use the second option.

    You will therefore need

  • Programmed microprocessor
  • PCB
  • Break out box
  • Microswitches on gear stick

    The shoppping list will consist of

    1* Programmed 16F84 PIC
    1* Main circuit board
    1* Break out circuit board
    2* Long arm microswitches
    2* 1N4148 diodes
    1* 100nF capacitor
    1* 470pF capacitor
    1* LM317 variable voltage regulator
    1* 78M05 5v voltage regulator
    2* TO220 Heatsink by Redpoint Thermalloy
    2* Bolts and nuts for fixing heatsink (?M2?M3)
    8* 150 ohm resistors (1/6W)
    1* 1600 ohm resistor (1/6W)
    2* 1000 ohm resistors (1/6W)
    1* 3300 ohm resistor (1/6W)
    1* 430 ohm resistor (1/6W)
    1* 240 ohm resistor (1/6W)
    1* 10 ohm resistor (1/6W)
    2* 1000 ohm variable resistors
    1* 5v reed relay
    1* Common anode 0.5" 7-segment display

    The PCB layout is available as a jpg (for printing direct onto Etch'n'peel transfer paper) or as a .pcw track file. This is for PCBCad from Hutson software. The .jpg image file has a 4.5cm line drawn along the bottom of the layout. When printing, do a test print first on paper to ensure that the image has not been magnified, otherwise nothing will fit..... This is not a problem when using PCBCad, though you will need to adjust the print settings so that it only prints the bottom layer. It is also a good option to change the bottom track colour to black from grey as you get better tracks.

    The circuit should be contained in a metal box or a plastic box lined with metal foil. Either way the screen metal should be connected to earth. With a metal box this can simply be achieved by bolting the box to an metal part of the chassis. With a foil screen try soldering or bolting a wire to the foil and bolt the other end to the chassis. Make sure the PCB tracks or component legs cannot touch the metal box/foil. The break out box can infact be simply wrapped in vinyl tape to protect it- a full box is not necessary.


     
     
    Project Part Download site Current status
    Program circuit diagram here Provisional
    Break-out box details here Provisional
    Complied 16f84 software Ver 2.0R (reversing gearbox) here Provisional
    16f84 source code Ver 2.0R (reversing gearbox) here Provisional
    Complied 16f84 software Ver 2.0R (electric motor reverse) here Provisional
    16f84 source code Ver 2.0R (electric motor reverse) here Provisional
    PCB file (.pcw format)   seperate 5v supply here Provisional
    PCB track (.jpg format)  seperate 5v supply here Provisional
    PCB component layout   seperate 5v supply here Provisional
    PCB file (.pcw format)   on-board 5v reg.  here Provisional
    PCB track (.jpg format)   on-board 5v reg.  here Provisional
    PCB component layout   on-board 5v reg.  here Provisional

    Questions? E-mail me here