Latch required?

[Wokyerdog]

I need to set up a circuit that uses tactile switches as inputs and led's as outputs and operates under the following conditions:

- two Led's each have a respective tactile switch
- pushing Button "a" turns on it's respective LED and stays illuminated until "a" is pressed again and then the light goes out
- if button "b" is pressed while the "a" LED is on, the "b" LED turns on also (BOTH LED's should be on at this point) until either "a" or "b" is pressed.
- pushing button "b" turns on BOTH LED's until either button is pressed and then they BOTH go out

I guess im mroe or less looking for the appropriate chip to use for this. I wish there was a way i could find some sort of directory to see what chip does what but I have a feeling that most of this application know-how just comes from experience.

-tim

 

[Reloadron]

What you need to do is get familiar with the truth tables for the families of flip flops. That would be your latch.

Ron

 

[ARandomOWl]

What you need to do is get familiar with the truth tables for the families of flip flops. That would be your latch.

Ron

This. It seems like you need something similar to a bistable latch. If you can draw up a truth table you will be able to construct what you want with a few basic logic gates.

 

[alec_t]

I wish there was a way i could find some sort of directory to see what chip does what

Google for flip-flops and latches then download the appropriate datasheets from the manufacturers. That will give you all the basic info you need to get you started.

 

[Mikebits]

Actually sounds like a state machine.

 

[Wokyerdog]

I understand some stuff about logic. (i.e. and gates, or gates, nor gates, etc). What i dont understand is how to really use them.

Say i have a chip that is full of "and" gates. pushing 2 switches together makes the output positive and it turns on an LED or whatever. How do you keep the light on? Does the light stay on until you hit the reset for the chip?

I think i understand what you guys mean about the latches though. These types of chips would sustain power to the output until a reset is enabled.

-wok

 

[Reloadron]

I understand some stuff about logic. (i.e. and gates, or gates, nor gates, etc). What i dont understand is how to really use them.

Say i have a chip that is full of "and" gates. pushing 2 switches together makes the output positive and it turns on an LED or whatever. How do you keep the light on? Does the light stay on until you hit the reset for the chip?

I think i understand what you guys mean about the latches though. These types of chips would sustain power to the output until a reset is enabled.

-wok

This is why I suggested getting familiar with Flip Flop circuits. They do exactly what you are looking to do. The point here becomes if I draw out a circuit doing what you want it to do then you come away from the table with nothing. The idea is to have you gain a basic understanding of not just AND gates but the family of gates and their associated truth tables. Flip flops are the next logical step.

Ron

 

[alec_t]

@Wokyerdog
You haven't, it would seem, followed up on the advice you were given in posts #2, #3 and #4.
Forum members will be reluctant to advise you if you ignore their advice.

 

[Gorgon]

Why not start at a manufacturer site and look through the different types of chips and their datasheets. Like www.nxp.com . Select 'logic' and start browsing.

 

[Wokyerdog]

I didn't mean to make you think that i ignored your advice. I DID look up some of that stuff, that's why i said that i understand some stuff about logic gates. I guess i was just looking for a more pointed direction of where to go and look. I don't mind looking stuff up but sometiems i just get overwhelmed by ALL the info that is out there. I still relatively new to this stuff but I'm doing my best.

-tim