Displaying the number (serial number) of closed switch using 7 Segment display.

Thread Starter

adityaabhi

Joined Sep 21, 2017
3
Hello, guys!!
I'm a mechanical Engg student so I need ur expertise on electronics.
problem: I want a circuit that displays the serial number of the closed switch in a row. To be precise, if no switches are ON it should display 0, if the first switch is ON then it should display 1, if the second switch is ON then it should display 2 and so on up to 6.

It is actually a gear shift indicator for my project, every shift puts a different wire in connection with the Engine (which is grounded in vehicles), whereas the neutral is an open circuit.

This circuit is to be attached to the dashboard of the vehicle, so if it can be designed w/o using Arduino(as said by the local project shop.) , it shall help with the packaging.
 

crutschow

Joined Mar 14, 2008
30,814
It could be done with a CD4532 priority encoder driving a CD4511 7-segment display driver.
The priority encoder generates a 3-bit binary number indicating which of 8 inputs is active (high).
This 3-bit number then controls the CD4511 to light the 7-segment display corresponding to the binary number.

The CD4511 has a 4-bit input for numbers 0 through 9 but you only need 3-bits for 0 through 7.
You just tie the 4th input (D) low (to ground).
 
Last edited:

Thread Starter

adityaabhi

Joined Sep 21, 2017
3
It could be done with a CD4532 priority encoder driving a CD4511 7-segment display driver.
The priority encoder generates a 3-bit binary number indicating which of 8 inputs is active (high).
This 3-bit number then controls the CD4511 to light the 7-segment display corresponding to the binary number.

The CD4511 has a 4-bit input for numbers 0 through 9 but you only need 3-bits for 0 through 7.
You just tie the 4th input (D) low (to ground).


Thanks , but i couldnt understand anything you said. is there a wiring diagram that you can provide me with?
 

crutschow

Joined Mar 14, 2008
30,814
Here's my first cut at a schematic using the priority encoder and display driver.
SW1 through SW6 are the gear selector switches.
I had to add a signal inverter at each switch output so that a grounded switch signal will give the required positive input to the respective priority encoder input.
The resistor values R1 through R7 depend upon the current requirements of the display you use.

upload_2017-9-24_11-40-2.png
 
Last edited:

Thread Starter

adityaabhi

Joined Sep 21, 2017
3
Here's my first cut at a schematic using the priority encoder and display driver.
SW1 through SW6 are the gear selector switches.
I had to add a signal inverter at each switch output so that a grounded switch signal will give the required positive input to the respective priority encoder input.
The resistor values R1 through R7 depend upon the current requirements of the display you use.

View attachment 135732
thank you very much...thats helpful.
 

AnalogKid

Joined Aug 1, 2013
10,126
Just to be clear, a priority encoder circuit like Wally's displays the highest switch position that is closed. It does not indicate which (if any) switches below that one are closed.

ak
 

absf

Joined Dec 29, 2010
1,968
I did a similar design for my friend many years ago. He is a good auto mechanic and he mounted 5 micro-switches inside the gear shift assembly (manual gear system). He wanted me to design a simple circuit that could display "F" when none of the contacts are making. The 5 gears would display "1, 2, 3, 4" and "A" which looks like "R" for reverse.

I did the circuit with 1n4148 diodes and resistors and a 74LS00 or 74LS08 chip ( couldn't recall clearly). And the circuit worked and he was very happy.

Allen
 
Top