1-4 Gear Indicator

[Lloyd]

Hi Guys!! I'm new in here and I'm new to electronics and have a little knowledge about it. I'm trying to do a project in where I have a car with manual gears 1,2,3 & 4. Each will be represented by a switch so altogether 4 switches. The switches are connected through a logic circuits and ended with a 7-segment LED.

When 1 is pressed, it displays "1" on the LED, When 2 is pressed, it displays "2" on the LED, When 3 is pressed, it displays "3" on the LED, When 4 is pressed, it displays "4" on the LED,

*NOTE; I need to represent the logic circuits as Diode-Transistor-Logic or Resistor-Transistor-Logic.. Can anyone here help me build the schematic for this project? I have very little knowledge on this stuffs.. So i got no choice but to seek for help! Thanks! Cheers

 

[alec_t]

Is this a homework or school project?

I need to represent the logic circuits as Diode-Transistor-Logic or Resistor-Transistor-Logic

Why?

 

[Lloyd]

It's a school project.. Basically, it's just a concept for my project.

It's the main requirement for project.

 

[kubeek]

Ok, start by choosing the 7-seg display - it will be either common cathode or common anode configuration. Then, for each switch connect a diode to every segment that should be lit when you press the switch. Don´t forget current limiting resistor on each segment.

 

[crutschow]

Your are aware that no one uses DTL or RTL logic anymore(?).

 

[KeepItSimpleStupid]

This is like boo/hiss. You can do that with a bunch of diodes and <=7 resistors. One for each segment needed.

 

[Misterbenn]

The OP might need to use logic if there has to be a combination of switches. for example switch 1 and 2 'on' for 2nd gear, and 1,2 and 3 for 3rd gear?

This would then need some AND logic and possibly some logic to detect incorrect combinations.

 

[KeepItSimpleStupid]

No, just like a car door switch can isolate two systems. You can diode or the two 1 segments together and wire OR the segments that make up a two and for the 3 and the 4.

The segments will all stay separated because of the diodes.

e.g. Connect Vcc through a resistor, the top left side segment a diode and terminal A of a switch. Then connect the lower side left the same way Vxx, resistor, segment, diode to point A. Connect the other side of the switch to ground.

Do the same for 2.

Two and 3 share segments. A diode will isolate them.

4 shares segments with ?

 

[absf]

Years ago, my friend/colleague who was very skilled in car mechanics installed 6 micro switches around the shaft of his car gear shift. Each micro switch was corresponding to one gear position. The commons are connected to the car body. He wanted me to design a simple circuit using TTL chips to display the 6 digits on a 7-segment LED with reverse gear indicated by "A" which looks similar to "R". When none of the switches were making, indicating a "neutral" position, the character "F" is displayed meaning "Free gear".

I completed the assignment with one 7400, 7 resistors and a handful of signal diodes and a 7805 voltage regulator. But I did not keep the schematics and that car must have been long gone by now. I might be able to recreate the circuit from memories if I have the time to do it.

cheers!

Allen

 

[alec_t]

I might be able to recreate the circuit from memories if I have the time to do it.

As this is a school project, guidance rather than a complete solution would be better. The OP needs to put some effort into this .

 

[crutschow]

Years ago, my friend/colleague who was very skilled in car mechanics installed 6 micro switches around the shaft of his car gear shift. Each micro switch was corresponding to one gear position. The commons are connected to the car body. He wanted me to design a simple circuit using TTL chips to display the 6 digits on a 7-segment LED with reverse gear indicated by "A" which looks similar to "R". When none of the switches were making, indicating a "neutral" position, the character "F" is displayed meaning "Free gear".
..........................

Sounds simple enough. But I would use a "0" for neutral (no gear).