How would I go about making a 7 segment LED display read off the numbers 1,2,3 and 4, when +12v is supplied from one of the 4 switches. While making shure that each circut is kept completely sepearate. I also have limited space where this display needs to go. Any Ideas?
Take 4 optocouplers and connect the diode sides to 4 switches and related 0Vs (through resistors) ..
These optocouplers will provide the required separation.
The other sides of optocouplers have transistors which collectors can be connected through a network of diodes to cathodes of 7-segment common anode LED displays (Emitters of these transistors should be connected to 0V) ..
For example, if you need to display "1" you will connect two diodes to segments B and C ..
Probably the same can be realized with 4 minature RLYs ..
so ive gotta drop the voltage to 0v with resistors, and connect a network of diodes? I understand this somewhat, but am partially lost. Any part numbers/datasheets I can look at of these optocouplers. And what is a "collector"? Maybe something else so i can draw it up on circutmaker and see exactly what I need to do and run simulations.
There are two examples on how to display numbers on 7-segment LEDs: one is activated by an optocoupler, the other one by a relay ..
The third picture shows how to use diodes in 4-in-1 combination and direct drive from voltages V1 - V4 through transistors ..
How would I go about making a 7 segment LED display read off the numbers 1,2,3 and 4, when +12v is supplied from one of the 4 switches. While making shure that each circut is kept completely sepearate. I also have limited space where this display needs to go. Any Ideas?
The solution from Ianp is very simple and effective. However if more than one of the input signals is active you will get a wrong display. Because the segments of the various inputs will be added.
Following the optocouplers. You can use a "priority encoder" like the CD4532 followed by a BCD to 7-Segment decoder/driver as the HCF4511.
This way you dont have to use a diode matrix to do the encoding and you get more inputs.
The CD4532 is has 8 bits and 3 bits output. (So you can display 0 to 7)
You may want to find a similar IC with 10 inputs and 4 bit output.
Note that I just give an example, please check the datasheets of the chips before building it.